CONTAINING POTASH. 441 



50 grains of picked crystals of tartar emetic were 

 dissolved in distilled water, and a current of 

 sulphuretted hydrogen gas passed through the 

 liquid as long as any precipitate fell. The hy- 

 dro-sulphuret of antimony thus obtained, when 

 dried in the open air, weighed 42*21 grains ; 

 but when heated in a glass tube, water was 

 driven off, and a black matter remained, which 

 weighed 24*59 grains, and which was sulphuret 

 of antimony, equivalent to 18*032 grains of anti- 

 mony, or 21*31 grains of protoxide of antimony. 

 The liquid thus freed from antimony, was 

 evaporated cautiously, and a quantity of bitar- 

 trate of potash obtained, which weighed 28*69 

 grains. But the integrant particle of bitartrate of 

 potash weighs 24*75 ; and 28*60 : 24*75 : : 21-31 

 : 18*384 = the protoxide of antimony united to 

 an integrant particle of bitartrate of potash. 

 Now, the protoxide of antimony weighs 6*5, 

 and 6*5 x 3 = 19'5 ; this is a little more than I 

 actually found, because part of the sulphuret 

 in my experiment adhered to the glass tube, and 

 could not be collected without loss. From this 

 experiment, which I thrice repeated, I have no 

 doubt that the constituents of tartar emetic are 



2 atoms tartaric acid . l6'5 



3 atoms protoxide of antimony 1 9-5 



1 atom potash . . 6-0 



2 atoms water 2-25 



44-25 



