78 
SUGAR OF LEAD FROM PYROLIGNOUS ACID, 
ON THE PREPARATION OF SUGAR OF LEAD WITH PYROLIGNOUS 
ACID. 
By G. Schnedermann. 
The pyrolignous acid employed for the manufacture of sugar of 
lead ought to be tolerably free from empyreumatic substances in or- 
der to yield a good product. The manufacturers of pyrolignous 
acid furnish (often under the name of muriate of lead) a product 
which is very brown by these empyreumatic admixtures, and which 
is prepared by saturating rectified pyrolignous acid with litharge. 
In dyeing and printing, sugar of lead is chiefly used for the prepa- 
ration of acetate of alumina ; but as impure sugar of lead is prejudi- 
cial to the more delicate colors, pure sugar of lead, prepared from 
alcohol vinegar, can alone be employed for these, as well as for 
chrome-yellow, chrome-orange, &c. 
Prof. Schnedermann, of Chemnitz, has discovered a method by 
which the sugar of lead may be obtained from pyrolignous acid in a 
sufficient state of purity for dyeing purposes. The rough pyrolig- 
nous acid is rectified in the usual manner, then super-saturated with 
slaked lime, and exposed to the air for twenty-four hours, during 
which time the mass is to be frequently stirred up. By the excess 
of lime, a great part of the empyreumatic matter, which forms with 
the lime a more or less brown and insoluble combination, is precipi- 
tated. The exposure to the air is necessary, because the empyreu- 
matic matters become more oxydized, assume a deeper color, and 
become fitted for combining with lime. The brown solution of the 
acetate of lime is then separated in a suitable manner from the pre- 
cipitate, and heated to boiling, when small quantities of a clear so- 
lution of chloride of lime are successively added as long as the li- 
quid continues to become paler. After evaporating to dryness, the 
yellowish-gray residue, which consists of acetate of lime, with a 
small proportion of chloride of calcium, is decomposed by sulphuric 
acid. If the acetic acid be intended to be obtained by distillation 
from this mixture, the sulphuric acid must be diluted with an equal 
volume of water. 
In other cases, the sulphuric acid is not at all to be diluted, or 
only very slightly so, and added gradually to the decomposed resi- 
due, to avoid the generation of heat. The mixture is left standing 
for a short time ; it is then to be diluted with water, and the clear 
