Vanadium (V) in conc H₂SO₄ gives a strong yellow coloration. A method based on an application of this phenomenon has been devised for the spectrophotometric determination of vanadium in iron and steel. The sample, after decomposition with perchloric acid, is treated with conc H₂SO₄ for the coloration of vanadium ; and the quantity of vanadium is sought by estimating the light absorbancy at 390 mμ using a solution prepared from pure iron treated in the same way as the sample solution as a standard solution. Or, the sample, after decomposition with perchloric acid, can be treated for the separation of iron and other metals by magnetic electrolysis with the use of a mercury cathode. Then the vanadium is colored with conc H₂SO₄ as above, and the light absorbancy is estimated, using water as a standard solution.

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The distillation of carrier-free ruthenium by ceric sulfate oxidation in sulfuric acid solution had been investigated for the isolation from mixed fission products. The yield of distillation was somewhat lower than the permanganate or the bichromate method. But the decontamination factor by the present method was good. Charactericity of these three different methods has been dis-cussed.

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In continuance of the preceeding reports, detection of tertiary amines in the xylidine fraction has been carried out by a combined use of infrared absorption spectroscopy and the liquid-liquid extraction method. The results indicated the presence of an unknown tertiary amine in an intermediate fraction between 2, 3, 4, 6-tetramethylpyridine and 2, 3-cyclopentenopyridine. The structure of this substance was confirmed to be 2, 3-cyclopenteno-6-methylpyridine ; the estimated content of this substance in the tertiary amine separated from the xylidine fraction was 16 %, or 5 % of the xylidine fraction. Also, a quantitative determination of 2, 3, 4-trimethylpyridine isolated at the same time was carried out.

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A tablet machine for the potassium bromide tablet method has been made, and quantitative determinations by infrared absorption spectroscopy have been carried out on a solid mixture composed of J-acid [2, 5, 7-H₂N(HO)C₁₀H₅SO₃H] and γ-acid [2, 8, 6-H₂N(HO)C₁₀H₅SO₃H], and a solid mixture of amino-J-acid [2, 5, 7-H₂NC₁₀-H₅(SO₃H)₂]and amino-G-acid [2, 6, 8-H₂-NC₁₀H₅(SO₃H)₂]in potassium bromide tablets. These mixtures can not be determined by the solution method, but by this tablet method satisfactory results have been obtained. The results of estimation of standard mixed samples of isomers composed of J-and γ-acids indicated that the standard deviation of them was 1.7 %, and that of standard mixed samples of amino-J-acid and amino-G-acid was 1.4 %.

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In continuance of the preceding Report III, the spectrochemical analysis of copper alloys by the use of the C. R. L. Universal Source Unit has been investigated. This report deals with the quantitative determination of aluminum, iron, nickel, and manganese in aluminum bronze, and also with an investigation of the effect of structure of sample on the spectrophotometric determination.
For these purposes, 3 kinds of samples of casted product were used : that prepared by a slow cooling in a sand mold, that prepared by rapid cooling in a metal mold, and that prepared by annealing.
The results indicated that the samples prepared by rapid cooling or those prepared by annealing can be determined with good accuracy within 3 % of standard deviation of error when a suitable selection of spark is made. The metallurgical history of the sample had two effect on the reproducibility and on the estimating line; the former was attributed to a local segregation in a rough scale, due to the large grain size, and the latter was attributed to the shifting of the estimation line by the "complexity" of metallurgical structure.

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In order to simplify and speed up the procedure for quantitative determination of Mg in Al alloys, the EDTA titrimetric method has been applied and the following procedure devised. The sample is decomposed with 20 % NaOH and 20 % KCN; the ppt. is filtered off, and taken up in HCl (1 : 1) ; Al and the other metals are precipitated as hydroxides; and Ca is precipitated by the addition of saturated (NH₄)₂C₂O₄. The solution containing the precipitates is treated with 20 KCN for masking of Cu, Ni, Mn, etc., and the Me²⁺ in the solution is titrated with a standard EDTA solution using EBT as an indicator. By the use of this method, the quantitative determination of Mg in Al alloys can be shortened to 30 minutes with as good reproducibility as that of the standard method.

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Thermal decomposition of tungsten ores with hydrochloric, sulfuric, or phosphoric acid, and heating of the resultant product with sulfuric acid to a temperature at which white fumes were evolved produced a solution. The solution was filtered, diluted to a definite volume, and a portion of it was used for photometric determination.
Since the coloration by reduction of the sample solution acidified with sulfuric or hydrochloric acid gave a lower value, the solution was made alkaline with NaOH ; but still it was not possible to obtain the coloration as above with an error less than 1 %. Therefore, the sample solution was heated to fuming with sulfuric and phosphoric acids, and the coloration of the product by reduction showed a linear relationship with the amount of tungsten when the amount of tungsten was less than 2.1 mg. Thus, the sample solution in 10 cc H₂SO₄ and 2 cc H₃PO₄ was heated to white fuming in 5 minutes, cooled, and 810 cc water and 20 cc HCl were added. The solution was then reduced with 3 g SnCl₂, colored with 5 cc water and 10 cc 10 % KSCN, and made up to 100 cc with water. The intensity of color through an S 43 filter plate and a 1 cm layer was estimated. Application of this method to ores containing less than 50 % WO₃ and a comparison of the results with the JIS method showed that the maximum error was 0.5 % and the average error was 0.30.02 %.

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When a solution of silicic acid is reacted in about 1 N sulfuric acid medium with the hydrofluotitanic acid-hydrogen peroxide reagent (a mixed solution of sodium fluotitanate, sodium fluoride, and hydrogen peroxide), the yellow color of pertitanic acid, in an amount equivalent to that of silicic acid, is developed. This is due to the greater stability of hydrofluosilicate complex-ion as compared with that of hydrofluotitanate. Colorimetric determination of silicic acid by the use of this color reaction was carried out. By observing the absorption at a wave-length of 420 mμ, and at a concentration of the solution between 2 mg/20 cc and 14 mg/20 cc of SiO₂, to which had been added 4 cc of the reagent of concentration 0.05 M with respect to titanium, a reproducible standard line was obtained. The apparatus used in handling the reagent and the reaction mixtures, as well as the absorption cells, were all made of synthetic resin.

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[in Japanese]

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[in Japanese]

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