title stringlengths 0 1.13k | abstract stringlengths 1 15.7k | PMID int64 22 36.5M |
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High frequency titration methods in the investigation of complex formation. | High frequency titration is a valuable tool in the study of complex formation in solutions, and the breaks in the titration curves can be used, in conjunction with the results of other physical methods, to determine the composition of the complexes formed. High frequency titration and other methods have been used to study the complexes formed by thorium, indium, plutonium(V) and boron with various complexing agents, and to develop methods for the determination of thorium and yttrium in rare earth mixtures, and of indium in the presence of zinc, cadmium, aluminium, nickel and cobalt. | 18,960,079 |
Precipitation from homogeneous solution applied to the drop technique for the study of nucleation. | The technique of precipitation from homogeneous solution has been successfully coupled with the drop technique for study of the nucleation process. | 18,960,081 |
Precise determination of uranium in pure uranium and uranium compounds by constant-current coulomeric titration. | A procedure is described for very precise determination of uranium in high-purity uranium and uranium compounds. Uranium(VI) is reduced in a concentrated hydrochloric acid solution by metallic aluminium in the presence of cadmium ions to uranium(III). This is oxidized to uranium(IV) by protons on addition of an excess of orthophosphoric acid, and then oxidized to uranium(VI) by adding a weighed quantity of potassium dichromate in small excess. The excess of potassium dichromate is determined by constant-current coulometry. The coefficient of variation does not exceed 0.003%. | 18,960,095 |
[L'application des radioisotopes a la chromatographie sur colonnes de celluloses substituees-IV L'analyse du mercure et du zinc dans le bismuth]. | The Chromatographic behaviour of nanogram amounts of bismuth has been studied by radioisotope techniques on cellobiose, cellulose and seven substituted celluloses. All celluloses in ethyl ether adsorb bismuth, provided that it is as nitrate, and that excess of nitric acid is avoided. Bismuth can be eluted with thiocyanate in ether-methanol or with hydrochloric acid in methanol, depending on the retention strength of the various functional groups of celluloses. A very simple method of separation of bismuth from mercury over a wide range of concentration is presented. | 18,960,099 |
Precipitation from homogeneous solution by photochemical action: determination of thorium. | Thorium was precipitated from homogeneous solution by photochemical reduction of periodate to iodate in a solution containing thorium and perchloric acid, by means of a 2537 A low-pressure mercury vapour lamp. For weighing, the precipitate was redissolved, precipitated once as thorium hydroxide, and finally as thorium oxalate, which was ignited to thorium dioxide. Quantitative results were obtained in the range 35-180 mg of thorium. | 18,960,114 |
Rapid microchemical method for the determination of magnesium in biological fluids. | A photometric method for the determination of magnesium in the presence of up to 50-fold excess of calcium is described. A magnesium-Azovan Blue lake is formed, stabilized with polyvinyl alcohol, and the absorbance is measured (Kodak No. 7 filter). The method has been used to determine magnesium in sera. | 18,960,134 |
1-Hydroxy-ethylidene-1,1-diphosphonic acid as a titrimetric agent. | 1-Hydroxy-ethylidene-1,1-diphosphonic acid (HEDPHA) has been proposed as a highly selective titrimetric reagent for thorium. In the presence of 1,2-diaminocyelohexanetetra-acetic acid (DCTA) a soluble binuclear ternary complex, Th(2)(DCTA)(2)(HEDPHA), is formed. The determination of thorium is carried out in a slightly acidic medium, buffered with urotropine, with 0.025M HEDPHA, and Xylenol Orange as indicator. DCTA masks all bivalent metals, rare earths, scandium, yttrium, bismuth, iron, gallium and indium. Only zirconium, titanium, aluminium and large amounts of thallium(III) interfere. | 18,960,136 |
Extraction of antimony with tertiary amines. | The extractability of antimony(III) and (V) with tridodecylamine from various aqueous solutions is reported. Extraction from nitric and hydrofluoric acid solutions is low, but extraction from sulphuric, hydrochloric and hydrobromic solutions is high. Antimony-(III) can be separated from antimony(V) in 7M nitric acid or 0.64M hydrobromic acid. The extraction of antimony from hydrochloric acid solutions in methanol, ethanol, and acetone-water mixtures is greater than from pure aqueous solutions of the same acidity. The elements from which antimony can be separated with tertiary amines are given. | 18,960,147 |
Kinetics of the precipitation of palladium dimethylglyoximate from homogeneous solution. | The kinetics of formation of palladium dimethylglyoximate in the post-nucleation and pre-nucleation stages, and the effect of palladium on the reaction of biacetyl and hydroxylamine, have been studied. | 18,960,161 |
APDC-MIBK extraction system for the determination of trace elements in saline waters by atomic-absorption spectrophotometry. | A technique has been developed for the determination of "soluble" cobalt, copper, iron, lead, nickel and zinc in saline waters by simultaneous extraction of their complexes with ammonium pyrollidine dithiocarbamate (APDC) into methyl isobutyl ketone (MIBK) and subsequent analysis by atomic-absorption spectrophotometry. Particulate matter is analysed separately by dissolving millipore filters in an acetone-hydrochloric acid mixture. Various analytical and instrumental parameters have been evaluated. The method is selfcompensating in that it makes allowance for any incomplete extraction of the complexes. The technique has been applied to the determination of these elements in sea-water and saline lakes. | 18,960,166 |
Solvent extraction of ammine complexes. | The ammine complexes of zinc and of cobalt(II) can be extracted effectively as the dipicrylaminates or tetraphenylborates by using nitrobenzene as the solvent. | 18,960,177 |
[Not Available]. | A physico-chemical study of the conditions of formation (pH, time, temperature) of dodecatungstates and of their separation with tetraphenylphosphonium chloride is presented. In the iso- and heteropolytungstate series only the anions of the form [XW(12)O(40)]((8-n)-(where n is the oxidation number of X) are precipitated by this reagent. The reaction is quantitative and can be used to separate the dodecatungstate from a mixture of tungstate anions. By using tetraphenylphosphonium chloride as a specific reagent for dodecatungstate it has been possible to show that in the condensation of sodium tungstate in high concentrations of acid the dodecatungstate begins to appear at pH ~ 6 and all the tungstate is in this form at pH ~ 2. Factors such as dilution, time and temperature also affect the formation of dodecatungstate over this pH range. The reaction is used for the determination of a series of dodecatungstates. | 18,960,179 |
Determination of sorbic acid with sodium chlorite. | A new method for the determination of sorbic acid is proposed, using sodium chlorite in hydrochloric add medium as reagent. In these conditions the hydrochloric acid is oxidized to chlorine which adds on to the double bonds of the sorbic acid. The addition is rapid (30-90 sec) and for this reason the determination is more rapid then others similar to it. Sorbic acid has been determined in foods by this method, after a preliminary solvent extraction or steam-distillation. | 18,960,193 |
Neutron activation analysis by standard addition and solvent extraction: Determination of impurities in aluminium. | A separation scheme based on selective extraction in conjunction with the standard addition technique has been developed for the determination of impurities in aluminium by neutron activation. Preliminary investigations have been carried out on the extractability of Sc, Co, Hf, Fe, Sn, Cd, Zn, Ag, Cr, Ce, Cs and Rb by TDA and TBP from acidic media. The best conditions are predicted for the separation of these elements into fractions suitable for analysis by gamma-ray spectrometry. Recovery values of approximately 90% were obtained for all the elements. | 18,960,206 |
A critical review of methods of isolating and separating the noble metals-III Chromatography, precipitation and fire assay. | This review deals with the chromatographic, precipitation and fire-assay methods of separating the seven noble metals, published subsequent to the previous reviews and prior to January 1966. The noble metal species present in solution are discussed in so far as they relate to separation and determination. | 18,960,211 |
Separation and acid equilibria of xylenol orange and semi-xylenol orange. | A mixture of Xylenol Orange (XO) and Semi-Xylenol Orange (SXO) was chromatographed on a cellulose column and ion-exchanged with Diaion SK-1 resin. XO and SXO in the acidic forms were titrated with sodium hydroxide to determine the basicities and the acid formation constants. The absorption spectra of XO and SXO were measured over a wide pH range, and were used for the calculation of acid formation constants, molar absorptivities, and the effect of ionic strength on the activity of XO. The purity of a commercial XO was measured by absorption spectroscopy, and it was found that the sample contained 36.3% of XO and 17.2% of SXO. Pure XO and SXO form a 1:2 and a 1:1 complex respectively with Zn(II). On the basis of these data the ionic structure of XO and SXO have been compared with those of Cresol Red and iminodiacetic acid, and discussed. | 18,960,230 |
The meaning of "sensitivity" in trace analysis. | The concepts of the ratio of the change in output signal produced by an increment of a material to be determined to that increment, and the smallest quantity of a material that can be detected "with certainty" are examined. The name "sensitivity" is suggested for the former, and "detectability" for the latter. Mathematical relationships are proposed that will permit the comparison of the detectability of two different analytical methods. | 18,960,242 |
Complexation reactions of dithiocarbamates. | The complexation reactions of various disubstituted dithiocarbamates are discussed. Special attention is paid to studies of composition and stability of various metal complexes. The conditions of complex formation in solution are treated in terms of side-reaction coefficients. The properties of metal-dithiocarbamate complexes are presented as a function of the nature of the substituents in the ligand molecule. | 18,960,244 |
Application of thermoelectric potential measurements in chemical analysis-II Determination of aluminium in iron alloys. | A method is proposed for the rapid determination of aluminium in iron alloys by means of thermoelectric potential measurement. An instrument has been modified, and a method devised for thermoelectro-analytical measurements. The thermoelectric potential of iron-germanium and iron-zinc alloys has been measured, and an attempt made at a theoretical explanation of the influence of alloying elements on the thermoelectric properties of transition metals. | 18,960,250 |
Electron spin resonance analysis of the redox indicator variamine blue II. | The oxidation of the redox indicator Variamine Blue in an aqueous medium has been studied by the ESR method. The optimum conditions for the formation of the radical have been determined. The spectra have in some cases shown hyperfine splitting, from which conclusions could be drawn for the nature of the oxidation reaction and structure of the oxidized product. The coupling constants have also been determined for the radicals. The correctness of the assumptions for the structure of the radicals has been supported by the simulation of spectra and the investigation of deuterated derivatives. | 18,960,255 |
Determination of critical micelle concentration of non-ionic surfactants by electrocapillary curves. | A method is described for the determination of the critical micelle concentration of non-ionic surfactants by measurement of their effect on the electrocapillary curves for a dropping mercury electrode. The method was compared with the iodine-solubilization, surface tension, and polarographic maximum suppression methods. | 18,960,267 |
Gravimetric determination of copper(II) with p-aminobenzoic acid. | A method has been developed for the gravimetric determination of 20-100 mg of copper(II) with p-aminobenzoic acid. Ag, Hg(II), Pb, Al, Fe(II), Bi, Sb(III) and Sn(II) interfere, but Zn, Co(II), Ni and Cd do not. The precipitate can be weighed after drying at 80-100 degrees , or can be ignited to copper(II) oxide at temperatures above 400 degrees , and weighed in this form. | 18,960,272 |
Volumetric determination of the U/O ratio in uranium oxides. | A method is given for determining the general formula UO(2+x), of sintered uranium dioxide pellets and uranium dioxide powders. Uranium(VI) is reduced by titration with iron(II) ammonium sulphate, after which the total amount of uranium is oxidized by titration with potassium dichromate. The end-points of both titrations are detected electrometrically. Determination of x in the range 0.0001-1.00 is possible. | 18,960,276 |
Determination of (3)H and (85)Kr in aqueous samples by liquid scintillation techniques. | Analytical procedures have been developed for the simultaneous determination of tritium and krypton-85 in aqueous solutions by liquid scintillation techniques. The effects of sample size, amount of water and dye were investigated. | 18,960,285 |
Polarography of molybdenum in aspartic acid solution. | The polarographic behaviour of Mo(VI) in solutions of aspartic acid is reported. In 0.01M acid, two waves are obtained, but at pH 4 only one, and they are diffusion controlled. The determination is possible in the presence of Ni, Cr(VI), W(VI), Mn(II), Co(II), Cu(II) or Th, with an accuracy of 2% in the range 10(-5)-10(-3)M. | 18,960,293 |
Improved method for the simultaneous absorptiometric determination of cobalt and nickel with quinoxaline-2,3-dithiol. | A new, more stable reagent, S-2-(3-mercaptoquinoxalinyl)thiuronium chloride (MQT), is proposed for the simultaneous absorptiometric determination of cobalt and nickel. It is hydrolysed rapidly to quinoxaline-2,3-dithiol (QDT) in ammonia buffer at pH 10. In the presence of zinc(II), QDT is stabilized by complex formation and the reagent blanks are reduced. Samples containing cobalt(II) and nickel(II) react with the mixture on warming to give 1:3 cobalt and 1:2 nickel complexes, with maximum absorbances at 472 and 520 mmu respectively. The sensitivity of the method is high, 0.0017 and 0.0028 mug cm (2) for cobalt and nickel respectively, and there is a significant improvement in accuracy and precision, which is about +/-1 % over a 15-fold change in cobalt to nickel ratio. The selectivity is moderate; Ag(I), Cu(II), Pd(II), Cd(II), Hg(II), Sn(II), Pb(II), Bi(III) and Pt(IV) cause significant interference but most other common cations and anions can be tolerated. | 18,960,307 |
Complexometric titration of calcium in the presence of larger amounts of magnesium. | A simple and accurate titrimetric determination of calcium in the presence of larger amounts of magnesium is proposed. Calcium is extracted into a small volume of organic solvent as its glyoxal-bis(2-hydroxyanil) complex, and the calcium is titrated with EGTA. The end-point is sharp, and occurs when the red colour of the organic layer vanishes. This method has been successfully applied to the determination of calcium in sea-water with an error less than 0.1%. | 18,960,309 |
Replacement substoichiometry and its application in activation analysis. | A new method based on the substoichiometry principle has been developed. Instead of substoichiometric amounts of chelating agent, substoichiometric amounts of aqueous solution of a competing metal are used. Theoretical relationships have been derived for this method of substoichiometric replacement. Possibilities for its application are discussed. | 18,960,317 |
Application of electroluminescence techniques to the determination of aromatic hydrocarbons. | An account is given of the quantitative determination of certain fused-ring aromatic hydrocarbons by means of the electroluminescence induced by application of a small a.c. voltage to inert electrodes placed in a solution of the hydrocarbon in dimethylformamide. | 18,960,335 |
Studies with dithizone--XII. Formation of thiadiazolines by condensation with aldehydes and ketones. | The red colour that develops when mineral acids are added to solutions of dithizone (I; 3-mercapto-1,5-diphenylformazan) in certain samples of dioxan is mainly due to the formation of 2-methyl-3-phenyl-5-phenylazo-1,3,4-thiadiazoline (II) derived in part from adventitious traces of 2-methyldioxalane. A purple compound of molecular formula C(13)H(10)N(4)S is also formed from (I) by an independent and slower reaction. The thiadiazoline (II) is readily prepared from (I) and acetaldehyde, but analogous compounds from formaldehyde benzaldehyde, acetone and ethyl methyl ketone are obtained in better yield by starting from diphenylthiocarbazide. Di-p-tolyldithizone gives similar reactions. Reduction of the thiadiazoline (II) [which has spectra very closely resembling those of 1:1 complexes of (I) with arylmercury (II) cations] with ammonium hydrogen sulphide in ethanol yields diphenylthiocarbazide by opening of the hetero-ring and elimination of an alkyl residue from the intermediate 3-alkylmercapto-1,5-diphenylformazan. Other examples of nucleophilic displacements from the formazan group by SH(-) have been investigated. | 18,960,368 |
Determination of part-per-milliard concentrations of mercury by atomic- fluorescence flame spectrometry. | A method is reported for the determination of mercury in the range 0.002-1 microg/ml . Mercury is extracted by dithizone from aqueous solutions into chloroform or isobutyl methyl ketone, the organic solution is aspirated into a hydrogen-oxygen name, and the intensity of atomic-fluorescence of mercury is measured. The method should be particularly useful for the determination of mercury in urine and for the determination of organic-bound mercury without prior decomposition. | 18,960,379 |
Coulometric titration of acids in non-aqueous solvents. | Coulometric titrations of mineral acids, sulphonic acids, carboxylic acids, enols, imides and phenols have been carried out in t-butanol or in acetone with electrically generated tetrabutylammonium hydroxide. Either a potentiometric titration or a visual indicator end-point may be used. The amount of acid titrated ranges from 10 to 60 muequiv, and the precision and accuracy of the method are excellent. | 18,960,387 |
Complexation of uranium by 2-(2-thiazolylazo)-4-methoxyphenol and 2-(2-thiazolylazo)-5-methoxyphenol. | A comparative study has been made of the complexation of uranium(VI) by 2-(2-thiazolyl)-4-methoxyphenol (TAMH) and 2-(2-thiazolylazo)-5-methoxyphenol(TAMR). The complexes are less stable and have lower molar absorptivities than the PAR and TAR complexes but are still useful for determination of uranium. The TAMH chelate can be extracted into isobutyl methyl ketone. Both complexes are 1:1 metal :ligand. For the TAMH complex log beta(1) = 8.8, = 1.4 x 10(4) at 610 mmu; for the TAMR complex log beta(1) = 8.1, = 2.0 x 10(4) at 530 mmu. | 18,960,388 |
Activation analysis for selenium and tellurium trace impurities in gallium, arsenic and gallium arsenide. | Destructive and non-destructive activation analysis for selenium and tellurium has been studied. In destructive analysis the selenium and tellurium activities are co-extracted from the irradiated and dissolved matrix elements with dithizone/CCl(4), reagent in a hot-chamber by remote manipulation, then separated from each other by diethylammonium-N,N-diethyldithiocarbamate/CCl(4) extraction, tellurium going into the organic phase and selenium being retained by the aqueous phase. The sensitivity of the method is 10(-8)g for both elements. By non-destructive methods, selenium can be determined down to 10(-6)g on short irradiation, and down to 3 x 10(-8) g on long irradiation and cooling, and tellurium down to 10(-6) g with long irradiation and cooling. | 18,960,391 |
Potassium-argon dating of the cape granite and a granitized xenolith at sea point. | Ages obtained by potassium-argon dating are reported for the total rock, light mineral fraction and heavy mineral fractions of the Cape Granite, and of a granitized xenolith derived from the Malmesbury sediments. These ages lie between 430 and 554 million years. The heavy mineral fractions from each rock type show the oldest age, 540 (granite) and 554 (xenolith) million years. These ages are interpreted as lower limits, and the granite age confirms the age of 553 million years found by rubidium-strontium dating. The coincidence of the ages of the different fractions of the granite and xenolith samples is discussed in the light of the different suggestions about the age of the Malmesbury sediments. The conclusion is reached that all pre-granitization history has been eliminated. The possibility of the use of argon retention as a measure of metamorphic activity is suggested. | 18,960,415 |
Mass spectra of some bivalent transition-metal ion chelates with pyridylazo phenols and naphthols. | The mass spectra of 2- and 4-(2-pyridylazo)phenol, 2-(2-pyridylazo)-1- and 1-(2-pyridylazo)-2-naphthol and several chelates of these compounds with manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) are discussed. Comparisons are made with the results of solution studies of complex formation of the same chelates. | 18,960,426 |
Mixing efficiency and instrumental delay effect on recorded kinetic curves. | The effect of reactant addition time and instrumental response time on recorded kinetic curves was considered. The mixing-time. effect was considered for first- and second-order reactions in the case that a simple function of the concentration is measured, and for first-order reactions in the more complex case of non-adiabatic enthal-pimetric measurements. For any ratio of addition time to half-transformation time the proposed equations allow calculation of the correct rate constant and the error in the calculated initial concentration extrapolated from the experimental curve and show which portion of the experimental curve must be disregarded owing to the misleading effect of the addition time. The distortion due to the response-time of a thermistor used as concentration transducer has been calculated from a simplified model. The experimental kinetic measurements performed by quasi- and non-adiabatic enthalpimetry agree very satisfactorily with the theoretical data. | 18,960,438 |
Spectrophotometric determination of some vic-diols. | Conditions have been established for the determination of mannitol and sorbitol (0.4-14 mug), mannose (3.6-18 mug), myoinositol (1.5-6 mug) and pinacol (11-70 mug) by periodate oxidation. The iodate formed is determined spectrophotometrically by reaction with iodide to form tri-iodide. Exce'ss of periodate is masked with molybdate. | 18,960,443 |
Polarographic investigation of syn-phenyl 2-pyridyl ketone oxime. | The polarographic reduction of syn-phenyl 2-pyridyl ketone oxime to alpha-(2-pyridyl)benzylamine over the pH range 0.78-12.88 is reported. Two waves are observed, both of which are pH-dependent. The complex electrode reaction is discussed and a mechanism advanced to describe the reduction of the oxime group over the pH range considered. | 18,960,447 |
Semipermeable ion-exchange membranes as a preconcentration matrix for trace analysis by electrochemical and neutron-activation techniques. | Ion-exchange membranes were used in conjunction with neutron-activation analysis and anodic stripping voltammetry for the determination of certain trace metal ions. The various parameters which govern the applicability, limitations and sensitivity of the methods were investigated. A new membrane "barrier" electrode assembly was introduced and found to be useful for the anodic stripping determination of trace metal ions in the presence of surface active materials. | 18,960,463 |
Fluorescence characteristics of inorganic complexes in hydrochloric acid medium at liquid-nitrogen temperature. | A study of the low-temperature fluorescence characteristics of the ions of 55 elements in concentrated hydrochloric acid is reported. The spectral characteristics, effects of hydrochloric acid concentration and time, calibration linearity and sensitivity for Sb(III), Bi, Ce(III), Pb, Te(IV), Tl(I) and Sn(IV) have been investigated. Uranium(VI), copper(I) and antimony(V) also exhibit fluorescence under these conditions. The detection limits using a commercial spectrofluorimeter with modified sample cells are Sb(III), 10(-6)M; Bi(III), 10(-8)M; Ce(III), 10(-7)M; Pb, 10(-8)M; Te(IV), 10(-7)M; Tl(I), 10(-6)M; Sn(IV), 10(-4)M. The suitability of some inorganic acid solvents for clear glass formation at -196 degrees is also investigated. | 18,960,467 |
Spectrophotometric determination of thallium with 4-(2-pyridylazo)resorcinol and 4-(2-thiazolylazo)resorcinol. | Thallium(III) gives sensitive reactions with PAR and TAR (epsilon = 2 x 10(4) at 520 nm), forming 1:1 complexes at pH approximately 1-2, and a mixture of 1:1 and 1:2 complexes at higher pH values; hydrolysis sets in above pH approximately 3. The stability constants are evaluated. | 18,960,469 |
A simple method for thermoanalysis of evolved gases. | Thermoanalytical processes involving the splitting-off of ammonia, water, halogens, inorganic acids or acid anhydrides can be simply observed by using a specimen-holder in which specific reactions with the decomposition products can be induced. A special glass or quartz double crucible can be used for this purpose; the products arising in the lower part of the crucible can be oxidized selectively with reagents placed in the upper part, or can be bound or transformed into other compounds. This double crucible is also suitable for studying reactions taking place between solid and gaseous substances. | 18,960,470 |
Determination of traces of perchlorate in chlorate solutions. | Perchlorate present in chlorate solutions is determined gravimetrically as tetraphenylphosphonium perchlorate after destruction of chlorate by addition of hydrochloric acid. Interference of Fe(III) and Cr(III) is prevented by complexing with tarartic acid. Replicate analyses of a sodium chlorate solution containing NaClO(3), NaCl, Na(2)Cr(2)O(7), and 390 ppm NaClO(4) showed 405 ppm NaClO(4) (standard deviation 19 ppm, 12 results). | 18,960,476 |
Extraction of vanadium into isobutyl methyl ketone. | Because of its advantages in atomic-absorption spectroscopy, isobutyl methyl ketone was chosen as organic solvent for an extraction study on vanadium. Of eight chelating agents which were evaluated for completeness of extraction, ease of use, working pH range, and freedom from interference, cupferron was judged best. | 18,960,477 |
Redox-complexometric determination of iron and cobalt and its application to the analysis of multi-component alloys. | A redox-complexometric determination of iron and cobalt is based on potentiometric titration of iron with EDTA, followed by that of cobalt with iron(III) chloride after addition of 1,10-phenanthroline. This method simplifies the complexometric analysis of more complicated materials. | 18,960,479 |
Studies on methylthymol blue-I Separation and purification of methylthymol blue and semimethylthymol blue. | The metallochromic indicator Methylthymol Blue was purified chromatographically with cellulose and ion-exchange resin columns. The monosubstituted product of the reaction, Semimethylthymol Blue, was also separated and purified, and can also be used for the colorimetric determination of metals. There are not marked differences between the infrared spectra of Methylthymol Blue and Semimethylthymol Blue. The purities of Methylthymol Blue and Semimethylthymol Blue finally obtained were above 97% and 90% respectively. In acidic medium Methylthymol Blue forms 1:1 greyish blue and 1:2 pure blue chelates with copper(II) whilst Semimethylthymol Blue forms only 1:1 orange chelates with bivalent metals. The molar absorptivities at 435 mmu are 1.89 (+/- 0.03) x 10(4) for Methylthymol Blue at pH 5.00 and 1.76 (+/- 0.03) x 10(4) for Semimethylthymol Blue at pH 5.45. | 18,960,484 |
Coulometric assay of the primary standards potassium dichromate and ammonium hexanitratocerate. | The high-precision coulometric titration apparatus of Eckfeldt and Shaffer (Leeds & Northrup Company) has been used for the precision assay of two primary standard materials for oxidation-reduction work. The purity found for NBS 136b Potassium Dichromate. 99.975 %, standard deviation 0.002 %, checks the earlier value of Marinenko and Taylor. Ammonium hexanitratocerate, if low in thorium, is also an excellent primary standard, two recent commercial preparations having purities of 99.972 and 99.984%, a higher standard deviation, 0.005 %, reflecting a minor difficulty in end-point detection caused by platinum oxide formation on the indicating electrodes. | 18,960,487 |
Collection of traces of metals on carboxy cellulose cation-exchanger. | Carboxy cellulose ("C-cell") is a cation-exchanger based on cellulose and having carboxyl functional groups with pK 3.46 +/- 0.05 at 20 +/- 1 degrees in 1M sodium chloride. The capacity of the exchanger is pH-dependent and the maximum is 0.22 mequiv/g. The capacity is also influenced by the dielectric constant of the medium and by the swelling of the cellulose. C-cell is suitable for the collection of metal ion impurities from aqueous and non-aqueous media. | 18,960,501 |
Separation of metal ions on tin(iv) tungstate and selenite papers. | Papers impregnated with the inorganic ion-exchangers tin(IV) tungstate and selenite have been shown to be useful for ion-exchange chromatography of several metal ion mixtures, and suitable solvent systems have been developed and evaluated. | 18,960,536 |
Resolution of racemic substances by liquid ion-exchange. | Two optically active liquid anion-exchangers have been synthesized. The separation factors of the enantiomers of sodium (+/-)-mandelate and sodium-N-acetyl-(+/-)-alanate have been determined by batchwise equilibration of aqueous solutions of the salts with chloroform solutions of each of the exchangers. Sodium mandelate has been resolved by Craig countercurrent extraction with one of these exchangers. Optically pure products can be obtained even though the liquid ion-exchanger is not optically pure. | 18,960,552 |
Oxygen determinations with the aluminium corrosion electrode. | A method for the determination of molecular oxygen in a great variety of liquid and gaseous samples has been developed. The method seems adaptable for control analysis by reason of its sensitivity, rapidity and ease of operation. It gives accurate determinations in the presence of many chemical substances which interfere with other methods. It is based on the variation in corrosion potential of the aluminium electrode, caused by oxygen, and exemplifies use of the corrosion phenomenon in analytical chemistry. | 18,960,568 |
A specific gas chromatographic detector for carbonyl compounds, based on polarography. | The evaluation of a specific gas Chromatographie detector for carbonyl compounds is described. This is based on the polarographic reduction of the Girard T hydrazone derivative which is formed when the carbonyl compound is absorbed in a buffered supporting electrolyte containing the carbonyl reagent. The detector was used to monitor the separation of a homologous series of alkanals. | 18,960,585 |
Solvent extraction-absorptiometric determination of niobium in steels with bromopyrogallol red. | A simple and rapid method is described for the determination of niobium in steel with Bromopyrogallol Red. After dissolution of the sample, niobium is extracted along with iron from concentrated hydrochloric acid into isopentyl acetate. Niobium and iron are stripped into an aqueous solution containing sodium acetate, and EDTA, ammonium chloride, tartaric acid, and Bromopyrogallol Red are added to complex the niobium. The niobium-Bromopyro-gallol Red complex along with excess of reagent is extracted into isopentyl acetate containing di-n-octylmethylamine, and measured at 610 nm. The molar absorptivity is 2.50 x 10(4) and Beer's law is obeyed up to 27 mug of niobium. The method is free from interferences and can be applied to the analysis of samples containing as little as 0.01 % niobium. | 18,960,586 |
Polarographic determination of aluminium with alizarin. | The polarographic determination of aluminium as its complex with alizarin in the pH range 9.2-10.1, with the cathode ray polarograph, is described. A solvent extraction procedure is used to eliminate interferences from many other metals. | 18,960,592 |
Effect of pH on concentration of species present in aqueous solutions of carbonyl compounds affected by hydration-dehydration and keto-enol equilibria. | Equations have been derived for hydration-dehydration and keto-enol equilibria of carbonyl compounds, showing the changes, with pH, of individual species present in aqueous solutions. An Egtran computer program has been constructed, so that the pH-variation of individual species for widely varying values of equilibrium constants can be evaluated. The treatment enables isolation of individual equilibrium constants from experimental data and identification of the system involved. The ratios of hydrated and non-hydrated, as well as of keto and enol forms, are pH-independent. | 18,960,598 |
Applications of digital computers in analytical chemistry-II. | This review deals with applications of digital computers to the evaluation of ionization constants of acids and bases, stability constants of metal complexes, concentrations of equilibrium mixtures, and the solution of rate equations. The use of computers permits systems of greatly increased complexity to be studied, and introduces additional methods of calculation such as numerical integration and Monte Carlo techniques. | 18,960,616 |
A simple low-power reduced-pressure microwave plasma source for emission spectroscopy. | The construction of a simple low-power microwave plasma source for emission spectroscopy is described. | 18,960,627 |
Activation analysis for mercury in biological samples at nanogram level. | A new method has been devised for determining mercury in samples of biological origin. It is based on complete ignition of the sample in a silica tube, trapping volatile interfering activities such as bromine or chlorine, and selectively adsorbing mercury on a strip of filter paper which has been previously impregnated with elemental selenium. This strip is later counted for quantitative evaluation. The versatility of the method has been demonstrated by the analysis of a wide range of samples such as water, cellulose, flour, fish solubles or animal blood samples with mercury contents between 1 and 200 ng g of sample. | 18,960,634 |
Determination of uranium in rocks by instrumental activation-analysis using epithermal neutrons. | A rapid non-destructive neutron-activation method for the determination of uranium in rocks is described. The method is based on activation with epithermal neutrons and subsequent measurement of the 74 keV gamma-ray of (239)U. Results given for some standard rocks are in good agreement with literature data. The precision of the method is about 5 % and the limit of detection is of the order of 0.1 ppm in silicate rocks. | 18,960,639 |
A triangular wave form generator. | A simple generator for triangular waveforms is described. It uses two operational amplifiers to give triangular waves between 0 V and a preselected voltage. The scan rate and limit can be varied independently. | 18,960,661 |
Spectrophotometric determination of palladium as tetraphenylarsonium palladium(II) trichlorostannate. | The optimum conditions for the formation of the complex, tetraphenylarsonium palladium(II) trichlorostannate, and its extraction into chloroform have been ascertained and a method has been developed for the spectrophotometric determination of microgram amounts of palladium in the presence of many other elements. | 18,960,666 |
A.C. polarographic determination of unsaturation. | A wide range of olefins can be determined by a.c. polarography of their addition compounds with mercuric acetate. The first step in the reduction of these compounds is a reversible, one-electron process to form the organo-mercury radical and gives a well defined a.c. peak. The optimum conditions for the determination of a representative selection of olefins has been established. | 18,960,677 |
The dissociation constants of alizarin fluorine blue. | Dissociation constants for the analytical reagent alizarin fluorine blue (3-aminomethylalizarin-N N-diacetic acid) have been determined by potentiometric titration at ionic strength 0.1, and are k(1) = 1.28 +/- 0.30 x 10(-5); k(2) = 2.82 +/- 0.24 x 10(-8); k(3) = 3.72 +/- 0.19 x 10(-11); k(4) = 6.39 +/- 0.12 x 10(-12). | 18,960,714 |
Hydrolysis of substituted 8-acetoxyquinolines. | In the absence of metal ions, the hydrolysis of 2-methyl-8-acetoxyquinoline and of 5-chloro-8-acetoxyquinoline follow the same reaction paths as those of the parent ester 8-acetoxyquinoline, including an intramolecular catalysis by the quinoline nitrogen. Unlike the hydrolysis of the other esters, that of the 2-methyl compound appears not to be catalysed by metal ions, and this is consistent with the view that catalysis by a metal ion involves the formation of a 7-membered chelate structure. | 18,960,716 |
Acid dissociation and metal chelate formation equilibria of some halogenated diphenylthiocarbazones. | The acid dissociation constants (K(a)) of di-p-fluoro-, di-p-chloro-, di-p-bromo-, di-p-iodo-and di-m-trifluoromethylphenylthiocarbazones and the equilibrium formation constants (K(f(1))) of their 1:1 complexes with Co(II), Ni and Zn have been determined at 25 degrees in 50% v v aqueous dioxan at 0.10 M ionic strength. Each of the electron-withdrawing substituents gives a reduction in pK(a) roughly proportional to its Hammett sigma value, and log K(f(1)) increases linearly with pK(a). | 18,960,717 |
Use of tetracyanoplatinate (ii) for the luminescent detection of metalions. | The tetracyanoplatinate(II) (TCP) ion forms insoluble fluorescent compounds with many metal ions. This property has not hitherto been exploited for analytical use. The soluble sodium TCP salt has been applied as a reagent for metal ion detection. Fluorescent precipitates useful for detection of the metal ions were obtained with Y(III), Zr(IV), Ag(I), Zn(II), Cd(II), Hg(I), Hg(II), A1(III), Pb(II), La(III) and Th(IV). Limits of detection ranged from 5 to 200 ppm. With ammonium acetate as a masking agent, selective detection of 10 ppm of silver was achieved in the presence of the other metal ions. As little as 20 ppm of zirconium can be detected in the presence of hafnium, which yields a non-fluorescent precipitate. | 18,960,718 |
Determination of vanadium in refractory metals, steel, cast iron, alloys and silicates by extraction of an NBPHA complex from a sulphuric-hydrofluoric acid medium. | A method for determining up to 0.15% of vanadium in high-purity niobium and tantalum metals, cast iron, steel, non-ferrous alloys and silicates is described. The proposed method is based on the extraction of a red vanadium(V)-N-benzoyl-N-phenylhydroxylamine complex into chloroform from a sulphuric-hydrofluoric acid medium containing excess of ammonium persulphate as oxidant. The molar absorptivity of the complex is 428 l.mole(-1).mm(-5) at 475 nm, the wavelength of maximum absorption. Interference from chromium(VI) and cerium(IV) is eliminated by reduction with iron(II). Common ions, including large amounts of titanium, zirconium, molybdenum and tungsten, do not interfere. | 18,960,775 |
Indirect determination of fluorides by the EDTA titration of samarium. | Fluorides are determined by the back-titration of excess of samarium with EDTA to the canary yellow end-point of Methylthymol Blue. The fluoride is precipitated and digested in a solution buffered at pH 2.5-3.0 with monochloroacetate buffer. After digestion, the pH is adjusted to 5.6-5.8 with pyridine and the excess of samarium is back-titrated in the presence of the precipitate, for samples with small quantities of fluoride. The procedure was used to analyse simple fluorides, fluoroborates and some other fluoro-complexes. | 18,960,777 |
Submicro determination of aluminium, bismuth and copper in organometallic compounds. | Methods for the determination of aluminium, bismuth or copper m samples of organometallic compounds weighing 40-110 microg have been developed. Spectrophotometric determination following digestion with nitric and sulphuric acids in a sealed tube is recommended, all results obtained from the analysis of standard compounds being within +/- 0.3% absolute error. Digestion in an open tube with perchloric and sulphuric acids gives satisfactory results for bismuth compounds but erratic and often low results for aluminium and copper compounds. | 18,960,783 |
Naphtho[2,3-d]-2-selena-l,3-diazole as a reagent for the determination of macro to submicro quantities of palladium. | Five analytical procedures, gravimetric, spectrophotometric, radiometric, fluorometric and atomic-absorption, have been developed for the determination of macro to submicro amounts of palladium. The methods are based on the reaction of PdCl(2), with naphtho[2,3-d]-2-selena-l,3-diazole. Analytical conditions such as the reaction time, concentration ranges, effect of pH and of 68 foreign ions, and solvent extraction were studied. Information relating to the structure and formula of palladium-piazselenol reaction products is included. | 18,960,791 |
Extractions with long-chain amines-I Extraction of some metal-xylenol orange complexes into methyltrioctylammonium chloride (aliquat 336-S). | The extraction of traces of metals forming intensely coloured complexes with Xylenol Orange in acidic medium (pH 0-3) has been studied. For such extractions in the presence of sulphates, chlorides and nitrates, a solution of methyltrioctylammonium chloride (Aliquat 336-S) in chloroform has been used. It is shown that it is possible to detect small amounts of gallium in indium and vice versa, and titanium or zirconium in thorium. These reactions should be capable of adaption to spectrophotometric determinations. The principle of the extraction of metals as their complexes with various metallochrornic indicators is briefly discussed. | 18,960,803 |
Sulphoxides as solvating reagents for the separation of metal ions. | The solvent extraction properties of the following sulphoxides have been evaluated: di-n-octyl sulphoxide (DOSO), bis(n-octylsulphinyl) methane (BOSM), bis(n-octylsulphinyl)ethane (BOSE) and p-tolyl sulphoxide (PTSO). By use of reversed-phase paper chromatography as a qualitative surveying technique, the interactions of these sulphoxides with some fifty metal ions were investigated in several acid-ligand systems. All sulphoxides were studied in 1-10M hydrochloric and nitric adds; DOSO and BOSM were also studied in perchloric acid and ammonium thiocyanate-perchloric acid mixtures. Observations are made concerning sulphoxide-metal interactions and the existence of several useful analytical separation systems is pointed out. The synthesis and characterization of BOSM and BOSE are described. | 18,960,806 |
Pyridine-2-aldoxime and 6-methylpyridine-2-aldoxime as gravimetric reagents for estimation of palladium(II) and uranium(VI). | Pyridine-2-aldoiumc (I) has been found to be a sensitive reagent for the gravimetric determination of palladium(II). From chloride medium, precipitation is complete at pH 3.0-11.0, and in solution containing 1NHNO(3) to pH6.0. The compositions of the precipitates (dried at 130 degrees ) correspond to PdL(2), and PdL(2). HNO(3) (HL representing the reagent) respectively. Pd(II) can be estimated gravimetncally in presence of acetate, oxalate, tartrate, phosphate, fluoride borate, perchlorate, Cu(II), Cd, Co(II), Fe(II), Ni, Zn, Pb, Bi, Sb(III), Pt(IV), Ir(IV), Ru(III), Rh(III); Os(IV) in quantities more than twice that of Pd(II), and Ag(I), Au(III) and Fe(II) even m traces cause serious interference. The yellow uranium(VI) complex with (I) is precipitated quantitatively over the pH range 3.5-10.5 and, after washing and drying corresponds to the composition (c(6)h(5)n(2)o)(2)uo(2), The uranium(VI) complex with 6-methylpyridine-2-aldoxime (II) is precipitated quantitatively over the pH range 3.0-10.5, and after washing and drying at 120-130 degrees corresponds to UO(2),(C(7),H(7),N(2)O)(2). Both (I) and (II) are suitable for the estimation of 1-50 mg of uranium(VI) in the presence of up to 10-fold quantities ofTh(IV), La(III) and Ce(III) even when present together. Ce(IV) in quantities more than three times that of U must be reduced to Ce(III). Tartrate, citrate, phosphate, Ti(IV) and Zr interfere, but acetate, oxalate, and borate do not. | 18,960,812 |
The complexes of bismuth(III) and nitrilotriacetic acid. | The reaction between bismuth(III) and nitrilotriacetic acid (NTA or H(3)X) has been investigated by ultraviolet spectrophotometry. It has been established that bismuth(III) and NTA form two complexes with compositions bismuth(III): NTA = 1:1 and 1:2. The absorption maxima are at 243 nm (1:1) and 271 nm (1:2), the molar absorptivities being 8.00 x 10(3) and 8.20 x 10(3) l.mole(-1).cm(-1) respectively. The stability constants (at mu = 1.0) are: log beta(BiX) = 17.53 +/- 0.06 and log beta(B)(2)(3-) = 26.56 +/- 0.07. The possibility of the analytical application of BiX is briefly discussed. | 18,960,814 |
Coulometric determination of uranium with a platinum working electrode. | Experimental conditions have been established which enable uranium to be determined coulometrically by the reduction of uranium(VI) to uranium(IV) at a platinum working electrode, by controlled-potential or controlled-potential-limit techniques. The procedure has been used successfully as a subsidiary method in the routine determination of uranium in pure uranyl nitrate solutions. The platinum electrode has several important practical advantages over the well established mercury-pool electrode for the coulometric determination of uranium. The consecutive determination of iron(III) and uranium(VI), or plutonium(IV) and uranium(VI) can be carried out with the same working electrode in the same solution and the coulometric oxidation of uranium(IV) to uranium(VT) is practicable. The rate of stirring of the cell liquor is much less critical in the case of the platinum electrode. Two main problems had to be overcome before a practical procedure could be achieved; hydrogen evolution during the uranium(VI)-(IV) reduction had to be eliminated so that 100% current efficiency could be obtained for the desired reaction and electrode-surface poisoning phenomena had to be controlled so that reaction times could be kept reasonably short. It was found that selection of a hydrochloric acid base solution containing a small amount of bismuth(III) enabled hydrogen evolution to be avoided: also electrode-surface poisoning with this base solution was not particularly serious and could be maintained at a satisfactorily low level by occasionally anodizing the electrode in dilute sulphuric acid. Bismuth(III) forms a complex with chloride ions and its presence increases the hydrogen overvoltage at the working electrode: no visible deposit of bismuth metal forms on the electrode during the uranium reduction. Samples containing nitrate can be analysed provided sulphamic acid is added to this hydrochoric acid base solution. | 18,960,821 |
Amperometric complex-formation titrations of traces of copper. | Copper has been determined in the submicrogram range by means of a eomplexometric titration with triethylenetetramine (TRIEN), the end-point being detected by following the anodic wave of the chelating agent at a rotating mercury electrode. The influence of the presence of other metals has been investigated both from the theoretical and the experimental point of view. Because of its higher selectivity TRIEN is preferred to other reagents of the EDTA group. The results show that copper can be determined in the presence of large amounts of most other metals. | 18,960,822 |
Optimum physical and chemical conditions for the Methylene Blue method of estimating gaseous sulphide in the environment. | The sensitivity and reproducibility of the Methylene Blue method for gaseous sulphide estimation have been investigated with respect to physical conditions and the concentrations of the reagents, especially sulphuric add. A new design of absorber is proposed to minimize gas-phase loss of the sulphide in the final stage of the procedure. | 18,960,830 |
Theoretical considerations on the estimation of sample matrix effects in analytical chemistry. | Methods are suggested for evaluating the magnitude of matrix effects on the results of analysis. | 18,960,832 |
Colour changes of chemical indicators-III: colour specification and its accuracy. | The systematic deviations involved in methods for computation of chromaticity co-ordinates have been studied for the specification of indicator colour changes. The weighted ordinale method (Deltalambda = 10 nm) has proved to be satisfactory for evaluation both of C.I.E. and complementary co-ordinates. The C.I.E. colour specification should be included among basic data about chemical indicators. | 18,960,882 |
Extraction of tungsten with 8-hydroxyquinoline and some of its derivatives. | The extraction of tungsten by chloroform solutions of 8-hydroxyquinoline(I), 2-methyl-8-hydroxyquinoline(II), 5,7-dibromo-8-hydroxyquinoline(III) and 8-mercaptoquinoline(IV), as a function of the concentration of tungsten and reagent and the acidity of the aqueous phase, has been studied. Evidence was obtained for the quantitative extraction of tungsten over a wide range of acidity. The degree of extraction of tungsten at 10(-5)M concentration with I,III and IV gives two maxima when plotted against acidity. The extraction maximum for the more acidic solutions lies in the region where the reagents exist in the protonated form and its position depends on the reagent used. It is suggested that different tungsten complexes are extracted, depending on the acidity of the aqueous phase. | 18,960,884 |
Spectrophotometric determination of cadmium in nuclear-grade Zircaloy-2 after selective extraction with a liquid anion-exchanger. | A method is presented for the spectrophotometric determination of cadmium in Zircaloy-2 at the tenths of ppm level. The method involves the extraction of Cd with tri-n-octylamine from 1M HCl, its separation from Fe(III) by scrubbing with tartaric acid, its recovery with 2M sulphuric acid, and the final development of the Cd-dithizonate colour. The method is simple and rapid, does not require any special instrumentation, and avoids the use of toxic reagents. Cadmium at the 0.3-ppm level has been determined with standard deviation 0.054 ppm. | 18,960,901 |
The error in absorption measurements, caused by the use of non-monochromatic light-I Parabolic functions. | The errors in absorption measurements in spectrophotometry, caused by the use of non-chromatic light, have been calculated. Parabolic functions have been assumed for the wavelength-dependence of the intensity of the incident light falling on the cell and of the absorbance of the compound measured. Results of the calculations may be used to predict non-linearity of absorbance-concentration curves or photometric titration curves. | 18,960,907 |
Film stripping voltammetry. | Film stripping voltammetry is a new electrochemical analytical method consisting in concentrating the test substance in the form of a metal or a sparingly soluble compound on the electrode surface and subsequently recording the current for electrodissolution of the deposit. The method has been worked out for determination of metal ions, anions and variable valence ions, with sensitivities as low as 10(-9)M. As indicator electrodes, solid, usually graphite, electrodes and stationary mercury electrodes are used. | 18,960,913 |
Spectrophotometric study and analytical application of rare-earth Tiron complexes-II Determination of europium. | The absorption spectra of europium-Tiron complexes in aqueous solution have been measured from 340 to 600 nm. The absorbance at 390 and 420 nm follows Beer's law up to 0.8 mg ml (pH 6.2-6.6). Other rare earths except for cerium(III) did not interfere. The interference of cerium could be removed by addition of ascorbic acid. The combining ratio of Tiron to europium has been found to be 1:1. | 18,960,925 |
Extractive spectrophotometric determination of micro and sub-micro amounts of fluoride. | A simple and sensitive extractive spectrophotometric determination of fluoride with the cerium(III)-alizarin complexan chelate has been investigated. The fluoro chelate formed is extracted into n-pentanol containing triethylamine. It is possible to achieve under selected conditions a selective extraction of the cerium(III)alizarin complexan-fluoride chelate. The stability of the chelate, the effect of temperature and the low absorbance of the blank are discussed. It is found that it is necessary to add a pH 9 buffer before the extraction. Procedures are given for the determination of 0.1-1 mug of fluoride in a 4-ml sample and 5-25 mug of fluoride in a 90-ml sample. | 18,960,940 |
Liquid-liquid extraction of lead(II) with tributyl phosphate. | Tributyl phosphate [30% solution in isobutyl methyl ketone (IBMK)] is used for the quantitative extraction of microgram amounts of lead from 3M hydrochloric acid containing lithium chloride (2M) as salting-out agent. It is then stripped from the organic phase with water and determined colorimetrically as its orange-red complex with 4-(2-pyridylazo)resorcinol at 520 nm. TBP alone cannot quantitatively extract lead in the absence of salting-out agents. The IBMK used as diluent does not extract lead under the conditions used. The period of equilibration needed is 5 min. Lead can be extracted in the presence of up to 100 times as much of certain other ions. The method is found to be applicable to analysis of gun-metal. | 18,960,950 |
Separation of rhodium from iridium with sodium borohydride and standardization of rhodium(III) solutions. | Of the platinum group metal separations, that of rhodium from iridium is the most difficult. The existing gravimetric methods are too lengthy or make use of organic reagents which ultimately need to be removed before iridium can be determined. The proposed method of separation is rapid, needs no pH control, and easy to carry out. Rh(III) ions are quantitatively reduced to Rh(0) by the action of aqueous sodium borohydride. The separation is best achieved in perchlorate medium in the presence of hydroxylamine. The separation is dependent on the concentration ratio of iridium to rhodium; if this is high, some iridium is co-precipitated; if low, the rhodium obtained is free from even spectrographic traces of iridium. A new method for standardization of Rh(III) solutions with sodium borohydride is proposed. | 18,960,952 |
[Not Available]. | A rapid simple method is described for the determination of carbon in organic compounds. The technique is based on a flash-combustion of the weighed sample (1-3 mg) in a hot empty combustion chamber at 950-1050 degrees and swept by a stream of oxygen at a rate of 80-100 ml min . Together with this flash and dynamic combustion in oxygen, a cupric oxide filling at 850 degrees is necessary. Halogens and sulphur oxidation products are retained by means of a silvered alumina filling at 750-800 degrees . Water and acidic oxides of nitrogen are absorbed at room temperature by means of magnesium perchlorate and manganese dioxide respectively. Carbon dioxide is absorbed in the cathodic compartment of an automatic coulometer and generates H(+) ions which are neutralized by OH(-) obtained by electrolysis. This method makes possible the determination of carbon in compounds containing halogens (including fluorine), phosphorus and metals. However, some metal compounds with polynuclear rings in their molecules give low results and require the addition of an oxidant to the sample in the boat for complete combustion. Vanadium pentoxide seems to be the best oxidant in the present working conditions. Solid samples are weighed and analysed in platinum or porcelain boats; liquid samples are weighed in Pyrex capillaries which are laid in platinum boats and covered with a small piece of platinum gauze. When normal liquid samples are analysed, one tip of the capillary is broken before its introduction into the combustion tube but in the case of volatile liquid samples the sealed capillary is introduced into the combustion chamber, where it explodes. The precision obtained is better than that of the classical methods. | 18,960,978 |
Synergistic effects in the solvent extraction of zinc with salicylaldoxime. | The extraction of zinc with salicylaldoxime was studied. The adduct-forming tendency of zinc salicylaldoximate with pyridine, alpha-picoline, beta-picoline, quinohne and isoquinoline was also investigated. This tendency decreases in the order beta-picoline > pyridine > alpha-picoline > isoquinoline > quinoline. | 18,960,989 |
Analytica chimica philatelica. | Notable contributors to analytical chemistry who have been honoured by postage stamps, and the significance of their contributions to the development of analytical chemistry, are reviewed. | 18,960,999 |
Microdetermination of alpha-amino acids by spectrophotometric and titrimetric methods. | Micro-methods for spectrophotometric and oxidimetric determination of alpha-amino-acids are described. They are based on a reaction of the acids with peri-naphthindan-2,3,4-trione hydrate at pH 2.5 to give a red precipitate of dihydroxy-peri-naphthindenone. The red product is dissolved and measured either spectrophotometrically at 243 nm or titrimetrically by reaction with iodine or N-bromosuccinimide. The results obtained by the three methods are concordant, the average recovery being 98 %. | 18,961,019 |
Determination of phosphorus in coke by the oxygen-flask method. | Recent developments in the oxygen-flask technique for determination of phosphorus in coke are described. The existing method was modified by use of the recently proposed potassium antimonyl tartrate catalyst for the ascorbic acid reduction of phosphomolybdate. | 18,961,029 |
Organic analysis by luminescence methods. | This review presents the major features of luminescence methods relating to the estimation of organic compounds in solution. A notation for reporting fluorimetric determinations is proposed. The outstanding factors affecting the fluorescence of solutions are briefly reviewed, and determinations of compounds offering a native fluorescence are illustrated by selected examples. Special attention is paid to functional fluorimetry and to the determination of non-fluorescent compounds by means of chemical reactions giving rise to fluorescent species. Some enzymatic reactions are described, as far as they allow the estimation of definite chemicals. Phosphorimetry and chemiluminescence are exemplified. An appendix presents some new functional fluorimetric determinations developed by the authors. | 18,961,032 |
Statocalcein, a stable Calcein indicator for the EDTA titration of calcium. | A dipotassium pentacalcium dicalcein salt ("Statocalcein") is recommended for use in place of Calcein as an indicator for fluorimetric titration of calcium with EDTA. The new indicator remains stable in solution for long periods (at least 210 days). | 18,961,041 |
The absorption of carbon dioxide in solutions of monoethanolamine. | Infrared, thermogravimetric and analytical results are presented that establish that the ethanolamine salt of 2-hydroxyethylcarbamic acid is formed when carbon dioxide is absorbed in solutions of ethanolamine. | 18,961,043 |
Oxidimetric determination of ascorbic acid with potassium hexacyanoferrate(III) in acid medium. | Conditions have been developed for the titrimetric determination of ascorbic acid with hexacyanoferrate(III), with potentiometric and visual end-points, in sulphuric, hydrochloric or phosphoric acid media. Several organic substances likely to be present in plant tissues do not interfere. | 18,961,044 |
Formation and composition of the precipitates of various metal 8-selenoquinoline complexes. | The effect of acidity on the precipitation of various bivalent metal 8-selenoquinoline and 8-mercaptoquinoline complexes has been systematically studied and compared. The metal ions were Zn(2+), Cd(2+), Pb(2+), Mn2+, Ni(2+), Cu(2+) and Co(2+). Most of the metal ions, except copper(II) and cobalt(II), precipitate as a. 1:2 complex, metal :ligand. However, in hydrochloric acid solution cadmium precipitates as CdR(2).2HCl and lead as PbR(2).2HCl or PbR.Cl. Copper(II) is reduced to copper(I) and precipitates as CuR.RH at pH above 2.0 and as CuR in strongly acidic solution. Cobalt(II) does not give a precipitate of composition but appears to precipitate as a mixture of CoR(2).RH and fixed CoR(2) or as other complexes. The reasons for the formation of the various types of precipitate are considered. | 18,961,076 |
Reaction rate methods in analysis. | A review is given of the principles and application of catalytic and reaction rate methods of analysis. | 18,961,109 |
[Détermination de l'or par réaction d'échange de complexes triples à association ionique]. | The principle of exchange of ion-association triple complexes has been used for photometric determination of gold. The effects of Pt, Pd, Tl and other elements have been examined, and conditions established for determination of gold(III) in their presence. | 18,961,124 |
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