Studies on Analysis of Calcium Cyanamide. (I·II)

Abstract

Results of quantitative estimation of dicyandiamide in calcium cyanamide by various methods do not always give agreement and there are considerable variation. Furthermore, these methods require a considerable time and there are many difficulties in their practical application. The present report deals with the studies on the effects of the amount of sample used, concentration of reagents, presence of impurities, and pH at the time of precipitation temperature and tiltrating condition in Harger or silver picrate method with the result that this is inaccurate in the presence of impurities, e. g. melamine and guanidine; a suitable to be applicable in such a case is established with higher accuracy and rapidity in comparison with heretofore known methods. A preliminary report on the corrected values of sulubilities is given.An improved Harger described in the first report gave accuracy and rapidity. However, the was not ideal in point of rapidity and further studies revealed that a satisfactory result was obtained by application of the formation of guanylurea nitrate from reaction of nitric acid. The is to add a certain amount of nitric acid to an extracted solution of calcium cyanamide, heat the mixture in a sealed container for 15 minutes at 100°C, the excess of nitric acid being estimated by titrating it with sodium hydroxide with an aim of estimations the amount of dicyandiamide from the amount of nitric acid consumed for the reaction. The time required for the reaction is 3 hours including the extraction, it does not require special reagents and its accuracy is ±3% of the content.