Abstract
Recently Iwasaki devised Ultramicro-Azotometry (AZM). In this report the author described a new method for iodine determination employing the Ultramicro-AZM. Previously at Biochemical Department of Kanazawa Medical College Iwasaki and Waseda reported of I2-Hydrazine-AZM which was not an ultramicro but micro method. In this process in order to prevent iodine evaporation, a large quantitative of potassium iodine had to be added while carbon dioxide being introduced into Azotometry. To prevent air oxidation of potassium iodide reagent or iodine liberation the AZM needed ice to cool and light to intercept. However, since a certain amount of potassium iodine oxidation was inevitable the above mentioned procedure was not satisfactory for the determination of ultramicro iodine.
The new method devised by the author is able to prevent effectively the oxidation of iodine. Saline solution is introduced and saturated bycarbon dioxide gas, then iodine potassium is dissolved in this solution.
As long as the introducing of carbon dioxide gas is continued this reagent will not be oxidized by the air. Utilizing this reagent the author was able to establish the ultramicro method for iodine determination. What interested the author the most was that this procedure enabled him to carry out the reaction in the absolutely anaerobic atomosphere.
Procedure
1. Suck up into the Ultramicro-Azotometer sulfuric acid and the test substance to be reduced by I- in acidity; for example KIO3, KMnO4, K2Cr2O7 etc.
2. The Azotometer will be brought to the state of a vaccume by replacing the inside air with carbon dioxide.
3. Introduce a small quantity of potassium iodide reagent.
4. Quantitatively liberated iodine will react with hydrazine in an alkaline solution in order to generate N2-gas which will be estimated by Ultramicro-AZM.
5. The amount of the test substance is calculated backward or retroactively.
For the iodine determination this method can be applied to 50∼2.5γ of iodine, with the possible error of not more than 1% for 50γ of iodine, of 2∼3% for 10γ of iodine, and of about 10% for 2.5γ of iodine.
The function of the Ultramicro-I2-Hydrazine-AZM is considered to be so accurate that this method is used for the calibration of the Azotometer itself.
