206 Dr. Gibbs’s Contributions to Analytical Chemistry. 
hydrogen, and in the filtrate from the sulphide of lead the alka- 
lies are to be determined in the usual manner; as there are no 
ammoniacal salts present the estimation of the alkalies offers no 
difficulty when they are in the form of chlorids. When but a 
single alkali is present its quantity may be determined by simple 
evaporation to dryness and ignition. The mass upon the filter 
after washing consists only of the peroxyds of lead and manganese. 
The filter is to be dried, ignited gently in a porcelain crucible, 
and then heated with fuming nitric acid which speedily produces 
a colorless solution. This is to be diluted sufficiently with water 
and the lead separated by sulphuretted hydrogen. The filtrate 
from the sulphide of lead contains only manganese which may 
then be determined as usual by carbonate of soda. In the above 
process it is almost always best to reduce the bases to be separa- 
ted to the form of chlorids.. The separation of the lead is much 
less easy when sulphates are present, while on the other hand 
the presence of nitric acid renders it difficult subsequently to de- 
termine the alkalies.. When however but one alkali is present 
with manganese, we may employ a solution of the nitrates, since 
in this case the alkali after the. separation of the lead may be 
estimated by fluosilicic acid and alcohol, as recommended b 
Rosé. When the solution of the bases is acid it may be neutral- 
ized with carbonate of lead, but this should be avoided if posst- 
ble, since it is not desirable to introduce more lead into the solu- 
Sains 
