208 W. Gibbs—Contributions to Chemistry. 
With crystallized sulphate of copper the following results 
were obtained. 
1°8435 gr. sulphate gave 81°89 p. c. acid and 31°70 p. c. base Raretiee | 
‘7183 gr. gave 82°14 « nd 8 8 
and 81°98 4 {Shar 
8'3955 gr. “ = gave 32:10 “ “ and 31:89 “ “ — (Tower) 
The formula €uSO, +5aq requires (Cu=63°50). 
I. II. Ill. 
€nO, 31°86 31°70 31°93 31°89 
S6,, 32°07 31°89 32°14 32°10 
The first analysis was made with a commercial sulphate, the 
other, with a pure salt prepared from electrotype copper. In crys- 
tallized sulphate of copper and potassium, (€uSO,-+K,5% 
6aq.) 26601 gr. gave 18-23 per cent acid and 18°11 per cent 
oxyd of copper. The formula requires 
Found. 
€u9, 18:00 18.11 
S9,, 18°12 18°23 
In the memoir already referred to Rose points out the neces 
sity of diluting the solutions of metallic nitrates to such a de 
gree that the nitric acid set free shall not act sensibly upon the 
sulphydric acid. 
n the experiments made in my laboratory to test the method 
this precaution was not found to be sufficient. Thus with crys 
pied nitrate of lead, Mr. Sharples obtained the following re 
ts. 
I. 2147 grams of salt were dissolved in 200 cc. water and 
e lead precipitated from the boiling solution by sulphydric 
acid gas. The filtrate was made up to 500 c. c. of which three 
eats milghvane vl 
oid *Y Sulphydric acid, and the excess of the latter ex 
from the Altres by boiling. i ded ae 
circumstances of the experiment. Precipitation from a boiling 
solution is 
0 obviate the difficult arising in the case of nitric acid 
; tO me to add to t e solution of the nitrate a portion of 
a neutral salt containin a fixed organic acid, an equivalen 
. of which would be set free ty the combination of = 
nitric acid with the base contained in the salt, This met 
