The loss of below 2 mg silver in cupeling was traced by use of radioactive silver, ¹¹⁰Ag.The experimental method consists of making a bead containing about 0.07 μc of ¹¹⁰Ag and determining the radioactivity of ¹¹⁰Ag in the bead and ¹¹⁰Ag in various parts of cupel after the cupellation for a direct determination of the loss by the absorption in cupel. This method made possible the making of a direct determination of the loss of silver in cupel, in a small amount which cannot be determined by the usual method and the tracing of silver in various parts of cupel is also possible. The result indicates that the loss of silver during the cupellation is exclusively caused by the absorption in cupel even when the amount of silver is small; and the smaller the amount of silver, the greater will be the loss of silver by the absorption in cupel.

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The methods of the quantitative determination of cobalt in nickel metal by the potentiometric titration method, the light absorbancy method, and the spectrographic method have been investigated. In the potentiometric titration method, the oxidometric titration method by use of heretofore known potassium ferricyanide has been investigated ; and the best conditions for removing disturbing influences, such as disturbing elements, oxidation by air and temperature, have been found for the accurate determination. In the light absorbancy method, various conditions for a direct extraction of cobalt as a antipyrine-thiocyanic acid complex salt with organic solvent from the nickel solution as well as the method for controlling of disturbing elements have been investigated and a satisfactory method has been found. In the spectrographic method, the sample solution containing nickel is absorbed in a carbon electrode and the methods of determination by use of an arc from alternating current have been investigated, in which the multi-line method gives a satisfactory result for the rapid determination.
A direct method of the determination of purity of high quality nickel metal has not been found up to this time. Although the electrolytic method has more merit than the other methods for the determination of nickel, methods known heretofore were found to be unsatisfactory for the determination of purity of high quality nickel metal. The greatest difficulty in the usual electrolytic method in ammoniac solution is an abnormally excessive deposition ; the studies on this problem have been very few and no satisfactory solution to overcome this difficulty has been found. Electrolytic studies of ammoniac solution in this experiment indicated that there were some other cause of the excessive deposition besides the excessive deposition caused by the adsorption of hydrogen gas at low temperature. In order to clarify this mechanism and overcome the difficulties, fundamental experiments were carried out in order to prove the consumption of platinum anode and its deposition on the cathode in the electrolysis of ammoniac solution. The quantitative determination of a small amount of platinum, nickel and cobalt in electro-deposit and residual electrolyte, as well as the efficiency of depolarizers, were investigated.

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High frequency titration of copper, nickel, and cobalt with the use of dithizone, dimethylglyoxime, α-nitroso-β-naphthol, and oxine has been investigated. Three methods were applied : (1) An indirect nonaqueous titration of liberated H⁺ in methanol and benzene mixture in the presence of an excess of organic reagent with NaOCH₃ ; (2) an indirect aqueous titration of the aqueous solution with NaOH in the presence of an excess of organic reagent ; and (3) a direct titration of the aqueous solution with the standard alcoholic solution of organic reagent. Titration of Ni in pH 11.7 in Table 3 was 1 mole 1 equivalent weight while all other cases were found to be 1 mole 2 equivalent weight. The results are indicated in Table 1, 2, and 3, and in the graphs. There were more examples of application of the indirect method than the direct method. In general, errors caused by observation are probably caused by adsorption. These methods are considerd hereafter to be useful analytical methods.

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A rapid analytical procedure of limestone has been investigated. In this method, calcium carbonate and magnesium carbonate are determined by disodium ethylenediaminetetraacetic acid titration ; and ferric oxide, aluminum oxide and silicic anhydride are determined by photometry. The precision and accuracy in this method are in good agreement with the A. S. T. M. value. Ten samples can be determined by one worker in one day. The time to analyse is one-forth and expense is one-half as compared with the former method. It can be applied to analyse similar materials, such as cement and dolomite.

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Mg²⁺ and Chrome Azurol S form a red to reddish purple lake in mixed solution of ammonium chloride and ammonium hydroxide. The maximum absorption of Chrome Azurol S is at 425 mμ and that of the lake is found at 580 mμ. There is practically no absorption at 580 mμ by the dye. The formation constant, log k, of the lake would be below 1, since its coloration is disturbed by tartrate ion. The separation of Mg from the bulk of the other elements in aluminum alloys is effected by a combined use of triethanolamine, sodium hydroxide and sodium cyanide after removal of silica. The determination of Mg²⁺ by photometric titration with EDTA at 580 mμ can be carried out by utilizing the masking action of triethanolamine and sodium cyanide.

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The iodine alcoholic method was established by Rooney Kobayashi. It was pointed out that the method was able to make the rational determination of MnO and FeO in steels which had been thought to be difficult by other determination methods of non-metallic inclusion.
But, for the practical application, this method has some difficulties in the use of the complex apparatus and it consumes much time.
In this point, we have made a study to improve it to make this method more easy and rapid.
Satisfactory results were obtained as follows:
(1) Since the original iodine method was difficult to make the complete decomposition of a sample, we used a magnetic stirrer apparatus to make the decomposition easier and also designed an apparatus to handle several samples at once.
(2) It was confirmed that there were no bad effects on the results obtained from the rapid filtration in the air, while the previous method required complex apparatus for the filtration in nitrogen atmosphere.
(3) After the examination of several standard samples, it was recognized that accuracy on the FeO and MnO values by this iodine method was fairly well when they were compared with the results of the vacuum fusion method and hot H₂SO₄ method.

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The quantitative determination of cerium (IV) in nitric acid solution by precipitation as iodate from other lanthanide elements can be carried out with good accuracy. But it requires much time and labor for washing of the precipitate, etc. Therefore, the so-called precipitation from homogeneous solution has been investigated, using ¹⁴⁴Ce and ⁴⁶Sc as the tracers. It was found that the formation of the precipitate was the best by using 3N HNO₃ solution. Futher investigation showed that the best precipitation method is carried out by the following method. Namely, at first, cerium (IV) should be reduced to cerium (III) by hydrogen peroxide, then potassium iodate and potassium bromate are dissolved at room temperature, and the solution is heated on a water bath for gradual formation of the precipitate of cerium which can be filtered and washed in a short time.

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Determination for trace amount of phosphorus in highly purified germanium oxide has been investigated. Colorimetric method with the molybdenum blue which was produced by extracting phosphomolybdate complex with butanol-chloroform solvent followed by reducing it with SnCl₂ was carried out in this research. Disturbing influence of As, Si, Zr, W, V in this method was avoided by removing or masking these elements prior to colorimetric measurements. Vanadium, which interferes most severely was separated by oxine-chloroform extraction with satisfactory result. A procedure for determination of μg P in GeO₂ was proposed. It was ascertained from results of analysis of GeO₂ sample using ³²P as a tracer that P, existing in order of 1 × 10^-5 %, could be determined by this procedure with error less than ± 10 %.

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A colorimetric determination of copper by extraction with carbon tetrachloride solution of zinc diethyldithiocarbamate has been investigated. This method gave a coloration in the presence of iron (III), cobalt, nickel, and bismuth but their disturbances were far less than when sodium diethyldithiocarbamate was used and showed to be a superior method on account of its simplicity. The following method was found to be good for avoiding the disturbing influences of these ions. Namely, the copper is extracted with carbon tetrachloride solution of dithizone, and the carbon tetrachloride layer is extracted with an aqueous solution of zinc bis (hydroxyethyl) dithiocarbamate for quantitative moving of the copper into the aqueous layer. The aqueous layer is then extracted with carbon tetrachloride of zinc diethyldithiocarbamate and the transmittance of the carbon tetrachloride layer is estimated. This method gives an accurate quantitative determination of copper in the presence of 1000 times as much of iron, manganese, cobalt, nickel, and silver.

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[in Japanese]

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[in Japanese]

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