288 



Bosworth — lodometric Determination of Silver 



titrated with jST/10 iodine, the titration giving a measure of the 

 silver originally taken. The details of these experiments are 

 given in Table I, B. 









Table I. 









KH 2 As0 3 added 



I a 



used 









i 



A ^ 



, 



_A ^ 





Error 



Silver 





Silver 





Silver 



Silver 



in terms of 



taken 





value 





value 



found 



silver 



grm. 



cm 3 . 



grm. 



cm 3 . 

 A 

 NH 4 OH 



grm. 



grm. 



grm. 







Use of 



with filtering 







0-1054 



20 



0-2000 



8-53 



0-0949 



0-1051 



— 0-0003 



0-1054 



20 



0-2000 



8-52 



0-0948 



0-1052 



— 0-0002 



0-1054 



30 



0-3000 



17-42 



0-1939 



0-1061 



+ 0-0007 



0-1159 



20 



0-2000 



7-60 



0-0846 



0-1154 



— 0-0005 



0-1054 



21 



0-2100 



9-37 



0-1043 



0-1057 



+ 0-0003 



0-1054 



20 



0-2000 



8-48 



0-0944 



0-1056 



+ 0-0002 







Use of 



B 

 NaHC0 3 



with filterin 



g 





0-1054 



15 



0-1618 



5-65 



0-0571 



0-1047 



-0-0007 



0-1054 



23 



0-2481 



14-14 



0-1430 



0-1051 



— 0-0003 



0-1054 



12 



0-1295 



2-40 



00243 



0-1052 



— 0-0002 



0-1054 



15 



0-1618 



5-60 



0-0566 



0-1052 



-0-0002 



0-1054 



15 



0-1618 



5-55 



0-0561 



0-1057 



+ 0-0003 



0-1054 



20 



0-2158 



10 91 



0-1104 



0-1054 



±0-0000 



0-2635 



35 



0-3776 



11-33 



0-1146 



0-2630 



— 0-0005 



Since the precipitate of metallic silver, in the experiments 

 of both A and B, was in a well coagulated condition, experi- 

 ments were carried on in which filtration was omitted, the 

 titration being made in the presence of the precipitate. The 

 results given in Table IT, A and B, show that the precipitate 

 has no appreciable effect upon the titration. If nitric acid 

 were present in the solution of the silver salt, as is usually the 

 case in analysis, it would be converted to a nitrate by the 

 addition of the alkali. In order to prove that the presence of 

 a considerable amount of sodium nitrate would not hinder the 

 reduction of the silver salt, determinations were made after 

 the addition of two grams of that substance, with the uni- 

 formly good results shown in Table II, C. 



Since in analysis it is often necessary to determine silver 

 when copper or lead or both are also present in solution, and 

 since silver can, with proper precautions, be separated from 

 either of these metals by precipitation with hydrochloric acid, 

 it seemed desirable to accomplish the reduction of silver when it 

 was in the form of the chloride. Consequently, determina- 



