OP ARTS AND SCIENCES. 47 



tially the same conditions as before. As thus modified, the method 

 gave exceedingly sharp results, and the whole course of the -analytical 

 process seemed favorable to extreme accuracy. The reduction of the 

 sulphide takes place at a temperature far below the melting point of 

 silver, — indeed, below a visible red-heat, — and the metal separates iu 

 a most beautiful fine filamentai'y condition, which very greatly facilitates 

 the reducing action of the hydrogeu gas. Here again, however, we 

 encountered another of those unforeseen constant errors which have 

 caused us so much perplexity and fruitless labor during the whole 

 investigation ; and we give in the following table a series of results 

 which have no other value than as illustrating the remark we have 

 before made, that no amount of accordance in the results of the same 

 analytical process is a sufficient guarantee against errors of this 

 class : — 



Reduction of Argentic Sulphide. 



First Series of Experiments at Full Bed Heat. 



f 



Weight of S, or Corresponding At. Wt. 



loss during reduction. of S when Ag = 108. 



0.1749 32.48 



0.1582 32.52 



0.3476 32.48 



0.2540 32.50 



0.4283 32.47 



0.3143 32.49 



0.3711 32.52*' 



Mean value . . ' 82.494 



Extreme variation from mean .026 



The sulphide used in the first five determinations was prepared from 

 washed chloride of silver, which was dissolved in pure aqua-ammonia and 

 precipitated with HgS -f- Aq., as described above. The portions used 

 in the last two determinations marked e and /were precipitated from 



* In this determination, the reduced silver fused. 



