Previously the author reported the Ultramicro-I
2-Hydrazine-Azotometry (AZM). In this report applying this method the author describes the ultramicro determination of I-, oxalic acid and Ca
++.
1) Ultramicro Determination of I-
Following the procedure of Feigl's spot test bromine water oxidates I- and changes it into iodate. Adds sulfosalicylic acid on this and the excess of bromine is decomposed Then applies the Ultramicro-I
2-Hydrazine AZM and the amount of I- will de calculated retroactively.
Characteristics
a) Since excess of sulfosalicylic acid exsists, sulfuric acid is not needed to add for the Purpose of iodine liberation.
b) By the introduction of carbon dioxide gas the trace of bromine vapor in the Azotometer will be removed and so there will be no reaction between bromine and potassium iodine reagent.
This new ultramicro method is able to determine 1-10γ of I- with the deviation of ± 5%.
2) Ultramicro Determination of Oxalic Acid
In the acid solution of sulfuric acid being added by Mn
++, reacting with oxalic acid, permanganate will be quantitatively redacted. Then as reported previously, permanganate will be measured by the I
2-H ydrazine-Azotometer. For this purpose, without adding oxalic acid, the volume of permanganate in the reagent will be determined.-(γ) Then a part of permanganate, which has been reduced by oxalic acid, will be determined by the AZM.-(β) The volume difference of γ-β is proportional to the amount of existed oxalic acid.
This ultramicro method is able to determine 0.25×10
-3 mol, 1ml-10
-4 mol, 1ml of oxalic acid with the possible error of not more than 5%.
3) Ultramicro Determination of Ca
++The principle of the Ultramicro-oxalic acid determination is adapted. In addition to this AZM, the author devised an apparatus which allows calcium oxalate to form precipitate, to collect quantitatively and dissolute easily and accurately.
Procedures
a) pH of Ca
++-solution is adjusted to 5.
b) The precipitate of calcium oxalate is formed by adding excess of ammonium oxalate.
c) The precipitate is filtered, washed by cold water and dissolved with sulfuric acid, liberating the oxalic acid.
d) The oxalic acid is determined by the application of the Ultramicro-oxalic acid-AZM.
e) The amount of Ca
++ is calculated retroactively. This method is possible to estimate 10-3γ of Ca
++ with the deviation of ± 3-4%.
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