DETERMINATION OF As IN ORGANOARSENIC DRUGS

A simplified method for the determination of arsenic content in various or- ganoarsenic drugs,such as Neoarsphenamine,Dichlorophenarsine and Acetarsone, is proposed,and a comparative study has been made of the use of a standard sample and the above mentioned drugs.The results obtained by this method is in good agreement with those obtained by the official methods adopted in several pharmacopaeias. Procedure:Transfer about 0,15 g of sample,previously chried and accurately weighed,into a 250-ml cortical flask with glass stopper.Add 5 ml of conc.sulfuric acid and 3 ml of nitric acid,shake gently and heat to boiling for 45 minutes. Cool slightly,add 1 g of ammonium sulfate and heat again for about 30 minutes until fumes cease to evolve and the soIution becomes coIorless.Add 50 ml of water and 6 ml of sulfuric acid,under cooling,and then add 1 g of potassium iodide.Insert the stopper and keep in a dark place for 30 minutes,and titrate the liberated iodine with 0.1N solution of sodium thiosulfate,using mucilage of starch as indicator.1 ml of 0.1N solution of sodium thiosulfate is equivalent to 3.746 mg of As.