204 Dr. Gibbs’s Contributions to Analytical Chemistry. 
the conclusion here deduced, that the weak point of this method 
is in the Catalogue places of the small stars used. ‘The steps 
which have been taken to obtain determinations of these, in con- 
nection with the Survey, I hope, also, to bring before the Asso- 
ciation. In the meanwhile, we multiply the number of pairs of 
stars, and make a number of observations on each pair; which 
would keep our results in due relation to those of the Catalogue, 
if much more perfect than at present. 
ani eneaeae 
Arr. XXIII.—Contributions to Analytical Chemistry ; by 
Woxcorr Gisss, M.D. 
In an interesting memoir* on the analogy between the chemical 
relations of peroxyd of lead and the so-called ozone, Schénbein 
has pointed out the remarkable fact that peroxyd of lead precipi- 
tates manganese completely from its solutions in chlorhydric and 
sulphuric acids, a compound of peroxyd of lead and peroxyd of 
manganese being formed. A portion of the lead is at the same 
time reduced to protoxyd and unites with the acid with which 
the manganese was combined: the oxydizing action which takes 
place may be represented by the general equation 
Pb O2:+MnO. XH=Mn O:+Pb X+HO. 
Schonbein appears not to have remarked the importance of this 
observation in an analytical point of view. In investigating the 
subject carefully I have been led to the conclusion that the per- 
oxyd of lead constitutes one of the most valuable reagents in 
analytical chemistry, since by means of it the oxyd of manga- 
nese may be easily and completely separated from a number of 
other bases without the employment of ammoniacal salts. The 
use of ammonia, as is well known, frequently renders analyses 
conducted by the ordinary methods laborious and inaccurate, 
either from the number of operations involved, from the absorp- 
tion of carbonic acid from the air, or from the unavoidable loss 
in driving off the ammoniacal salts by heat. The facts which 
I have determined and which serve as the basis of the analytical 
applications of the peroxyd of lead are as follows. : 
1. Peroxyd of lead completely precipitates manganese from 11s 
neutral solutions in chlorhydric, sulphuric, and nitric acids, slowly 
in'these cases, however, chlorine or oxygen is set free, and the 
quantity of lead dissolved is greater than that which corresponds 
an excess | 
