iodin were dissolved in a little alkali and diluted to definite volume 

 with water, the solutions so prepared being carefully kept in tightly 

 stoppered flasks and used for the experiments in Table 1. The 

 pipettes and flasks used had been standardized at the United States 

 Bureau of Standards. 



TABLE 1. Estimation of iodin in the presence ofchlorin and bromin. 

 SERIES A. (20 cc of solution= 0.2640 gram of iodin used.) 



SERIES B. (20 cc of solution =0.4885 gram of iodin used.) 



In order to test the applicability of the method to the estimation 

 of iodin in erythrosin a sample of this color was synthesized, the 

 fluorescein, prepared from Kahlbaum's resorcin and phthalic anhy- 

 drid, being completely freed from chlorids by repeated precipitation 

 from alkaline solution by acetic acid. This was combined with 

 some of the purified iodin just described, and finally separated as the 

 color acid. This preparation contained no halogen other than 

 iodin, of which the alkaline fusion method indicated 56.40 per cent, 

 as shown in Table 2. After further experimental work on the proper 

 proportion of reagents to be employed the following procedure was 

 adopted : 



Place from 0.3 to 0.4 gram of the erythrosin in a porcelain casserol, 

 dissolve this in 5 cc of a 10 per cent sodium hydroxid solution, then 

 add 35 cc of a 7 per cent solution of potassium permanganate. After 

 mixing, cover the vessel with a watch crystal, and add 10 cc of nitric 

 acid, keeping the dish covered. Agitate the mixture, place on a 

 steam bath, and keep covered until spattering ceases, after which 

 remove the watch glass and allow evaporation to proceed to dry- 

 ness. Treat the residue with 5 cc of 7 per cent potassium per- 



a In the operation of drying particular care should be observed to prevent access 

 of reducing gases to the mixture. 

 Cir. 65 



