240 



C. B. and J. B. Bhaduri — On Double Thiosulphates [No. 1, 



of thiosulphuric acid. Hence it was concluded that the substance was 

 a double thiosulphate of copper and sodium, and we confirmed it by 

 quantitative estimation of the acid. We estimated the thiosulphuric 

 acid both by the direct action of iodine on the salt acidulated with 

 hydrochloric acid, and by decomposing the salt with caustic soda, 

 filtering and titrating the filtrate by iodine after acidification. The 

 results are tabulated below : — 



1 CC IODINE SOLUTION = -01516 GRAM I. = '01365 GRAM H 2 S 2 3 . 



Table of direct titration with iodine solution. 





Wt. of Salt used 

 (Sample VII). 



Vol. of Thio- 

 sulphate required. 



Vol. of Thio. 



calculated for 



1 gr. Salt. 



Mean. 



Percentage of 

 H 2 S 2 3 . 



2909 gram. 

 01880 „ 

 0-3467 „ 



10-6 c. c. 



6-9 c. c. 



12-7 c. c. 



366 c. c. 

 36-7 c. c. 

 36-6 c. c. 



36-63 



50- 



B. 



Table of titration of the filtrate after decomposing the salt by NaOH and 



filtration. 



Wt. of Salt used. 



Vol. of Thio- 

 sulphate required. 



Vol. of Thio. 



calculated for 



1 gr. Salt. 



Mean. 



Percentage of 

 H 2 S 2 3 . 



> 1 

 „> [1-0637 gram. 



3- [1*5558 „ 

 S 



CO J 



0-6190 „ 

 19320 „ 



38-25 c. c. 

 53-5 c. c. 



22'0 c. c. 

 679 c. c. 



36' c. c. 

 36-3 c. c. 



36-3 c. c. 

 351 c. c * 



36-2 



49-3 



On comparing the two tables it is found that the result of table A 

 is slightly higher than that of B. The total sulphur 27*95 % if calcu- 

 lated as thiosulphuric acid would give 49'8 / o ; so that there is fair 

 agreement between the calculated result and that obtained by the 



* In this case the result is too low as the salt was slightly decomposed and 

 discoloured. 



