Although the Kjeldahl method has been used for the determination of nitrogen in organic compounds, there is a recent report for quantitative nitrogen determination by the use of strong phosphoric acid and iodic acid. However, the procedure of the latter method is rather complicated. The author made it possible to carry a continuous operation in a shorter time than the usual method by a slight modification of the operation as to non-volatile compounds such as amino acids and proteins. Namely, a gas buret similar to Van Slyke's apparatus for determination of amino nitrogen is used with some improvements on carbon dioxide generator and the determination can be carried out with an error within +0.5% margin of error.

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Rotary dispersions of 17 kinds of refined amino acids of known purity derived from natural_ proteins have been determined and its application. to analytical chemistry has been investigated.
(1) The value, [M] =A/(λ²-λ_c²) -B/λ², of simplified Drude equation of each amino acid was sought and it was compared with the curve prepared from experimental results.
(2) Graphical representations of λ²-1/ [M] were prepared and the results showed straight lines in all cases, except for tyrosine. By utilization of this finding, it was suggested that the test on purity of amino acids was possible.
(3) Ultraviolet absorption spectra of amino acids have been estimated and the relation between the wave length of the maximum λ_max, and λ_c (specific vibration wave length) obtained from rotary dispersion in Drude equation has been investigated.

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A wave which overlapped with that of copper in 10M sulfuric acid, shifted to the side of a more positive potential as the concentration of sulfuric acid became lower. Therefore the wave did not interfere with the determination of copper in 5M sulfuric acid. It was ascertained that the wave was caused by chloride ion since the wave height increased by adding sodium chloride. The chloride ion wave on the square wave polarogram was diminished as increasing the concentration of sulfuric acid over 8 to 12M. The temperature coefficient of wave height of chloride ion in 10M sulfuric acid was about 0.6% at 30°C. The calibration curve obtained with the scanning speed of D. C. applied potential of 0.2V/min, was less linear than that obtained with the scanning speed of 0.1V/min. The overlapped wave height of chloride ion and copper in 10M sulfuric acid was not precisely equal to the sum of each of the chloride ion and the copper wave.

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The optical rotation of mannitol is affected by the presence of boric acid. It is tried by the authors to determine boron by utilizing this phenomenon. To a 10.00 ml solution containing 025 mg of boron as borate is added 1.0g of mannitol and stirred to accelerate the dissolution. After three hours 2.0g sodium hydroxide is added and cooled. Difference between the optical rotation of the solution and that of a standard solution of mannitol under the same condition is proportional to a concentration of boron, and the sensitivity is 0.1 mg B per 0.01° optical rotation in 10 cm cell. The difference increases with increasing pH, and the calibration curve is bent near a point where the mole ratio of mannitol and boric acid is 2.4 : 1 under the above condition. Silicate, tungstate and aluminum ions interfere seriously. Molybdate, vanadate, chromate and zinc ions affect little, and fluoride, chloride, sulfate, nitrate and phosphate ions not. White precipitate appears when fluoride or phosphate ions are present in the above solution, but the optical measurement can be done satisfactorily with the supernatant.
The method is very simple when the interfering ions are absent, and will be extended for the determination of boric, germanic, telluric. molybdic, tungstic or uranic acid in combination with polyhydric alcohols, carbohydrates or hydroxycarboxylic acids.

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A simplified procedure for the determination of molybdenum in metallic uranium and in uranium oxide was proposed. The sample was dissolved in hydrochloric acid and hydrogen peroxide. Molybdenum in the solution was extracted into butyl acetate, and washed with dilute hydrochloric acid. The butyl acetate extract was shaken with the dilute hydrochloric acid solution containing ammonium thiocyanate, stannous chloride, and perchloric acid, and the color developed in the butyl acetate layer was measured at about 460 mμ. Satisfactory results were obtained over the range of 020 ppm of molybdenum.

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Determination of a trace of iron contained in uranium metal has been made by the spectrophotometric method using 1, 10-phenanthroline. In applying the method, influences of co-existing uranium are examined.
Two procedures are adopted;
(1) The sample is dissolved in hydrochloric acid and hydrogen peroxide. The solution is evaporated to dryness on the steam bath and dissolved in water. And then hydroxylamine hydrochloric acid, acetic acid, ammonium acetate and 1, 10-phenanthroline solutions are added. The red color of 1, 10-phenanthroline ferrous complex is measured by the light transmittancy of the sample solution at 508 mμ. In this case 10300 ppm of iron in uranium metal can be determined under the co-existence of uranium.
(2) The sample is dissolved in hydrochloric acid and hydrogen peroxide. Ferric iron is reduced to ferrous by sodium thiosulfate. Uranium is separated by TBP-C₆H₆ extraction. Adding hydrogen peroxide and bromine water, ferrous iron is oxidized again, and is extracted with TBP-C₆H₆. Iron is back-extracted with water from organic layer, and then spectrophotometrically determined in the same way as in (1). In this method 260 ppm of iron can be determined. This method of seperation has been examined by using ⁵⁵⁺⁵⁹Fe as a tracer, and found to be adequate for the purpose.

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Determination of a trace of manganese contained in uranium metal has been made by the spectrophotometric method with permanganate. The sample is dissolved in hydrochloric acid and excess nitric acid. Hydrochloric acid is removed by evaporation. Uranium is separated from a nitric acid (46N) solution with TBP-CCl₄. Sulfuric acid is added and the solution is heated to fume, and water, silver nitrate and ammonium persulfate solution are added and boiled. Manganese in the sample solution is oxidized to permanganate. The color of permanganate is measured by the light transmittancy at 525 mμ. When 2g of sample is taken, and the volume of permanganate solution is made up to 10 ml as low as 2 ppm manganese in uranium metal can be determined.

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A simple and accurate method for determination of arsenic in cast iron and carbon steel has been investigated. Samples are dissolved in nitric acid, fumed with perchloric acid to expel the remaining nitric acid, then residue is treated with the 1 : 1 mixture of concentrated hydrochloric acid and titanium trichioride aqueous solution, and transferred into a separatory funnel. To the obtained solution, added sufficient pottassium iodide or hydroiodic acid to give its concentration 0.5M or over and arsenic is extracted by benzene as arsenic triiodide. The arsenic in benzene is back-extracted into water, then, after oxidized to quinquevalent state, converted to a heteropoly blue compound by treatment with ammonium molybdate and hydrazine sulfate. The transmittancy of the blue compound is measured through a 750 mμ filter.
In this method, P, Si, Mo, V and Sn do not interfere. Arsenic in original cast iron and carbon steel is determined by taking O.10.5g of these samples.
Analyses of several standard samples were made with relative error of ±3% and time required for an analysis was about 90 minutes.

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[in Japanese]

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[in Japanese]

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