236 ANALYSES OF METALLIC IMPLEMENTS. 
out with water, and the solution filtered upon ashless paper; and when the residue 
was large the process of fusing and extracting was repeated. If the operation 
was successful, the solution now contained as sodium sulpho-salts all the tin, anti- 
mony, and arsenic of the insoluble residue. The residue and filtrate were treated 
separately. 
III. TREATMENT OF THE RESIDUE AFTER THE SULPHUR FUSION AND EXTRACTION. 
(a) If the original material was pure metal, the material upon the filter, 
containing possibly sulphides of lead, copper, and iron, was ignited, and the 
residue was treated with aqua regia and a little sulphuric acid. The mixture 
was heated to the fuming point of sulphuric acid, cooled, and treated with a little 
water. Any precipitate of lead sulphate at this point was filtered off on asbestos 
and weighed. 
The solution, filtered if necessary from precipitated lead sulphate, was treated 
with ammonium hydroxide and any precipitated ferric hydroxide was filtered off 
and weighed as ferric oxide. 
The solution containing no ferric salt, or filtered from the precipitated ferric 
hydroxide, was treated with hydrogen sulphide and any precipitated copper sul- 
phide was filtered off, ignited, and weighed as copper oxide. 
(b) In case the original material was corroded material contaminated with 
siliceous and earthy substance, the procedure in treating the residue after the 
sulphur fusion and extraction was varied. In this event, the material remaining 
upon the filter might consist of siliceous and earthy substance as well as small 
amounts of copper, lead, and iron sulphides. This residue was ignited with the 
filter, in platinum, and treated with hydrofluoric acid and a few drops of sulphuric 
acid. ‘The mixture was heated until the free acid had been removed and was then 
ignited and weighed. The loss of weight under the treatment with hydrofluoric 
acid should be silica, in the absence of material capable of yielding undecomposable 
sulphates. If the material contained bases, like lime or soda, which formed with 
sulphuric acid,refractory sulphates, this measure of the silica was only approximate. 
The residue after the volatilization of silica was fused with sodium carbonate, 
the mass after fusion was treated with hydrochloric acid, and hydrogen sulphide 
was passed into the solution. Any precipitate of sulphides thus obtained was 
filtered off, ignited, and treated for the formation of lead sulphate, ferric oxide, 
and copper oxide, according to method described in the preceding paragraph (a). 
IV. TREATMENT OF THE SOLUTION OBTAINED AFTER THE SULPHUR FUSION AND EXTRACTION. 
The solution obtained by extracting with water the mass remaining after the 
fusion with sodium carbonate and sulphur was acidified with hydrochloric acid. 
The precipitate containing sulphur, and possibly sulphides of antimony, arsenic, 
and tin, was collected upon a small filter, the filtrate being rejected. The precipi- 
tate upon the filter was dissolved in the least possible amount of a warm solution 
of sodium sulphide. The solution was concentrated, cooled, and treated grad- 
ually with sodium dioxide until the liquid became colorless and oxygen was liber- 
