82 
ON WHITE LEAD. 
carbonate of lead, through which carbonic acid is passed to 
fully carbonate it. The chloride of lead is also treated with 
nitric acid, and carbonated in a similar manner. Farther, 
lead is dissolved in nitric acid, and precipitated by a caustic 
alkali, or earth. This patent is evidently complicated, per- 
haps too much so for practical purposes, and unless the 
patentee employs a mixture of carbonated with caustic alkali, 
I do not know how he is to obtain a hydrate with a little car- 
bonate; I would rather reverse it, and say carbonate with a 
little hydrate. By employing red lead with the chloride, the 
metal is oxidized by it, so that chlorine, and not hydrochloric 
acid, is the result; but why should the evolution of chlorine 
be connected with a white lead establishment? 
Leigh's patent, Rep. Pat. Inv., vol. xiv., 1840, employs 
first, nitric acid to act on galena, to obtain a nitrate of lead; 2d, 
carbonate of ammonia purified from gas liquor, or from the 
distillation of organic substances; 3d, decomposes the nitrate 
by this carbonate, obtaining carbonate of lead and nitrate of 
ammonia; 4th, decomposes the sulphate, or chloride, of lead 
by carbonate of ammonia. In consequence of the amount of 
litharge produced collaterally in several branches of art, the 
action of nitric acid on galena appears to be no improvement, 
particularly as a portion of the acid is decomposed and lost 
by yielding oxygen to the lead to form the whole of the ox- 
ide. If the carbonate of ammonia can be obtained at a cheaper 
rate than those of soda, or potassa, and of a suffi ient degree 
of purity, the process might be a good one, but this may be 
questioned, and even if a sulphate or a muriate of ammonia, 
be obtained, for which there is a ready sale, I question whether 
the process would then be economial. 
It is not necessary to enumerate more of these highly che- 
mical processes, for it must be evident to any one acquainted 
with the present state of chemical science, that they might be 
varied "ad infinitum." The main questions are the economy 
of the processes and the quality of the material produced. 
In reference to the former point, I would merely remark that 
I doubt much whether such processes can be successful, 
