220 Analysis of a Magnetic Iron Pyrites. 
(from the whiting) and sulphohydric acid passed through it to 
saturation. The precipitate, containing much free sulphur, was 
filtered, washed and digested with sulphohydrate of ammonium. 
A black precipitate remained, which after washing was oxydized 
by nitric acid, filtered and precipitated by hydrate of potassa after 
addition of some ammonia, and thus after filtering, washing, dry- 
ing and incinerating, yielded oxyd of copper 0-075 grammes, or 
1:50 per cent., equivalent to 1:197 per cent. metallic copper. 
5. The filtered potassic solution from the oxyd of copper (§ 4) 
became dark by the addition of a few drops of sulphohydrate of 
ammonia and deposited a black precipitate, which, collected in 
a counterpoised filter and dried in water-bath, weighed 0-019 
grammes or 0°38 percent. This, dissolved in diluted nitric acid, 
yieded by addition of diluted sulphuric acid an abundant precipi- 
tate of sulphate of lead.’ The filtered solution from this yielded, 
by a current of sulphohydric acid, an inconsiderable amount of 
ning of copper amounting to 0-003 grammes or 0:06 pet 
cent., Equivalent to 0-04 per cent. metallic copper. The above 
er cent. contained, therefore, after deduction of the sulphu- 
ret of copper 0:32 per cent. sulphuret of lead, equivalent to 02 
per cent. metallic lead. 
6. Th 
per cent. which calculated as oxyd is equivalent to 0°032 pe 
tric acid with the addition of chlorohydrie, till the sulphur be- 
came perfectly yellow. The solution was filtered an ; 
