BER aeons eke NIE 
W. Gibbs—Contributions to Chemistry. 209 
was found to give perfectly satisfactory results, as the following 
analyses by Mr. S. P. Sharples will show. 
4.409 grams of nitrate of lead were dissolved in 200 c.c. of 
water, five or six grams of pure Rochelle salt added and the 
lead precipitated as above. The quantity of acid found corres- 
ponded to 82°58 per cent. The formula Pb(N®,)2 requires 
Found. 
N,©,, 32°63 32°58 
PbO, 67°37 67:27 
09880 gram of nitrate of bismuth were treated as above, 
Rochelle salt being added. The nitric acid found, corresponded 
‘40 per cent and the equivalent quantity of oxyd of bis- 
muth to 47°82 percent. The formula Bi(NO,),+10aq requires 
Kr F 
Bs Oss 33°47 33°40 
Bi,O5, 47-94 47-82 
5°6558 gr. of chlorid of mercury were treated as above, six 
or eight grams of Rochelle salt being added to the solution. 
The free acid corresponded to 
Calc. nd. 
Clas 26°20 26°10 
Hg, 73°80 73°90 
When the compound to be analyzed contains 
an excess of free acid not combined with the oxyd of the metal 
to be determined, this must be first separated by np, a: to 
apne in the usual manner. The presence of alkalies and 
Ikaline earths is of course without influence on the result, but 
On the other hand even very small quantities of iron, alumina 
1 various other bases make it almost impossible to determine 
the point of saturation with precision, these oxyds in solu- 
- Hon giving with cochineal and logwood specific reactions not 
sily distinguished from those produced by the alkalies in ex- 
cess. For this reason the method does not apply when oxyds 
of this class are present, and this case is preci ly that which 
—_Szconp SentEs, VoL. XLIV, No. 131.—Sepr., 1867. 
