80 
ON WHITE LEAD. 
a report by the Franklin Institute, (Journal for 1839,) and I 
find that the same views are held by Mitscherlich, in vol. ii., 
of his Elements, Berlin, 1840. Benson alludes to a similar 
view, (Jour. Frank. Inst., vol. xxv., p. 197,) but refers it 
chiefly to his process, (see above.) I have given my opinions 
more at large on this subject, since some of the most eminent 
chemists have advanced the opinion, and I believe it is gene- 
rally held, that the formation of carbonate of lead by the 
old process depended mainly on the decomposition of acetic 
acid. 
C. Newer processes. — I have understood that experiments 
were performed many years since, with the view of making 
white lead, by the introduction of vapour of vinegar, air, and 
carbonic acid, into heated apartments containing lead, but as I 
am unable to find the authority for this, I shall pass to those 
with which I am acquainted. 
Mr. Ee Clark took out a patent in 1S28 for a process for 
making white lead in close chambers, heated by steam, into 
which he introduced carbonic acid and air, the vinegar being 
in a trough, and running through the chamber, and heated by 
steam passing through its double bottom, (Jour. Frank. Inst, 
vol. xxv., p. 232.) Richard's patent was taken out subse- 
quently, and differed in the introduction of steam into the 
chamber, besides some minor differences of arrangement. I 
should suppose that the vapourized vinegar would afford suf- 
ficient steam, as in the first patent, the object being merely to 
ensure the action of the other materials. 
It will be observed that the process, chemically speaking, 
is the same in these patents as in Thenard's method, or the 
older processes, viz., that an oxide and acetate are formed 
and decomposed by carbonic acid. 
The carbonate formed by the above processes, the older and 
newer, is composed of two atoms of carbonate, and one of hy- 
drate of lead, but the difference between them and Thenard's 
lies in the crystalline granular state of the latter, while in the 
former " the leadlias not departed from the solid state," and 
is therefore more compact or amorphous, and has greater body. 
