KI0 3 used 



Wt. of I for 1- 



11 . 8 cc 



•00848&" 



23-6 



•00846 



_ 



•00847 



350 G. S. Jamieson — Determination of Mercury. 



In order to test the method, a solution of potassium iodate 

 was standardized with pure sublimed iodine, using Andrews' 

 titration under the same conditions as are described beyond 

 for the mercurous chloride titration. 



Iodine taken 



A '1003S 



B -1998 



Average _ 



Since the reaction in the case of iodine is represented by the 

 equation 



41 + KI0 3 + 6HC1 = KC1 + 5IC1 + 3H 2 



the strength of the potassium iodate solution was l cc = *01572 g 

 of HgCL 



For the following titrations a sample of pure mercurous 

 chloride which had been dried at 130°-135° C. for several 

 hours and well pulverized was used. The titrations were car- 

 ried out in a glass stoppered bottle of 250 cc capacity in the 

 presence of 20 cc of water, 30 cc of concentrated hydrochloric 

 acid, and 6 CC of chloroform, with thorough shaking of the 

 closed bottle between the additions of the potassium iodate 

 solution. As is usual in such titrations, the chloroform globule 

 at first increases in iodine color and then this color is gradually 

 removed. The end-point is the disappearance of this violet 

 color. It was observed that dried mercurous chloride reacts 

 more slowly in this operation than the precipitated substance 

 which was titrated without drying in some of the experiments 

 to be described beyond, so that in this case very thorough 

 shaking and occasional crushing of the lumps with a glass rod 

 were required. The following table gives the results of the 

 titrations : 



HgCl taken KI0 3 cc. HgCl found Error 



I -4999S- 31-80 '4999^ "00002 



II -5000 31-80 -4999 '0001 



III -5005 31-80 -4999 —'0006 



IV -6001 38-15 -5997 - -0004 

 V -4999 31-80 '4999 '0000 



The results show a very satisfactory agreement among them- 

 selves and with theory. 



Since most kinds of organic matter do not interfere with 

 this method of titration, it is applicable to various mixtures 

 containing calomel. It was tried with calomel tablets contain- 

 ing milk sugar, after pulverizing several tablets to obtain a 

 uniform mixture. Quantitative determinations of the calomel 

 were also made by treating portions of the substance with 

 water slightly acidified with hydrochloric acid and weighing 



