Abstract
For the determination of SO42- contained in oceanic salts, the author investigated a rapid analytical method of chelatometric titration, gravimetric method and others to make some improvements and obtained the following results:
1. In general, the chelatometric titration of Ba2+ in the presence of barium sulfate tends to bring about a negative error. Therefore, the author investigated to avoid this error by addition of ethyl or methyl alcohol and equivalent quantity to Ba2+. As the result, a visible change in color at the end point was observed by addition of alcohol to the sample solution, and the change of EBT-indicator was clearly observed in the presence of Mg2+ of more than 0.7 equivalent quantity to Ba2+. It was found undesirable to apply this method as it was to the magnesiumio n containinmg ore than 20 equivalenqtu antityt o SO42- such as the brine produced by ion-exchange membrane method.
2. The author used Ba-EDTA to investigate a simple method of determining sodium sulfate and magnesium chloride contained in common salt.
3. The direct precipitation analysis method of SO42- was improved by using the rhodizonic acid paper test.
4. Taking advantage of the fine grain precipitation obtained by the reaction of Ba-EDTA, the uthor determined the micro SO42- by turbidimetric analysis. This method gave satisfactorya results to the determination of micro SO42-.
