OP ARTS AND SCIENCES. 39 



this exceedingly hygroscopic substance from contact with moist air, 

 and all the transfers were made in a portable photographic devel- 

 oping chamber, the air of which was kept dry by dishes of sulphuric 

 acid. The portions for analysis were transferred, in tliis chamber, to 

 tightly fitting weighing tubes; and, after the weight was taken, they 

 were dissolved in a concentrated aqueous solution of tartaric acid, using 

 about 5 grammes of tartaric acid to each gramme of chloride of anti- 

 mony. The solutions were then diluted, and precipitated with argentic 

 nitrate, weighing out in each case the amount required, so that only 

 the least possible excess of the reagent should be added. The precipi- 

 tates were washed and collected by reverse filtering in platitium or 

 porcelain crucibles, and dried in an air bath at temperatures varying 

 from 110° to 120°. They were weighed with the small disk of paper 

 used in this jirocess, and the invariability of the weight of these paper 

 disks was repeatedly tested. Also, in several instances after removing 

 the filter, the argentic chloride was heated to incipient melting ; 

 but, as in no case was its weight thus altered, this additional pre- 

 caution seemed unnecessary. In the determination numbered 17, an 

 attempt was made to ascertain whether the presence of antimony in 

 the tartaric acid solution appreciably influences the precipitation of 

 argentic chloride. In this analysis, the antimony was first separated 

 from the solution by HgS ; and, the excess of this reagent having been 

 removed by warming the filtrate with a small amount of ferric nitrate, 

 the chlorine was precipitated in the usual way. The result, as will be 

 seen, agrees as nearly as could be expected with those obtained by at 

 once precipitating the chlorine from the antimony solution ; and it was 

 not until some time subsequently that the causes of error referred to on 

 page 5 were discovered. 



The letters in the following table indicate different preparations, 

 thus : — 



a was made from a crj'stallizecl chloride of Veron and Fontaine, Paris, 



which was purified in the manner described above. 

 b was made from a crystallized chloride marked Rousseau Freres, Pari s, 



purified as before. 

 c was the same as b, again distilled and crystallized. 



d, the same as c, after ten additional distillations. 



e, the same as d, again distilled below 100° in a current of dry hydrogen 



gas. 



/ was made with a crystallized chloride from Merck of Darmstadt, purified 

 by repeated distillations and subsequent crj'stallizations from bisul- 

 phide of carbon, after first treating with chlorine as described beyond. 



g, same as /. but in this determination the antimony was first precipitated 

 from the solution. 



