LEAD IN VARIOUS ARTIFICIAL PRODUCTS. 303 
ART. LXIV. — ON THE PRESENCE OF LEAD IN THE 
STATE OF OXIDE OR SALT IN VARIOUS ARTIFICIAL 
PRODUCTS. 
By M. Chevreul. 
I am induced by several motives to publish some facts 
with reference to the presence of lead in the state of oxide 
or salt in various products of the arts, not because these 
facts of themselves are of great importance, but, on account 
of the many consequences which may be deduced from 
their knowledge, they present a certain interest. 
I have had an opportunity afforded to me of pointing out 
to the Academy the inconvenience which may occur from 
treating woollen tissues with metallic matters, susceptible 
of producing with the sulphur which they naturally contain 
colored sulphurets, when these tissues are either to receive 
impressions on a white or light-colored ground, or to be 
dyed by similar colors, because under the influence of the 
heat or steam, or of the liquid serving as a dye bath, a 
colored sulphuret is formed spreading over all the portions 
of the tissues which are impregnated with the metallic mat- 
ter. Some months back I was asked what might be the 
reason that the shawls woven in Picardy six months ago, 
on coming into contact with steam, became of a brown tint, 
even without having received any previous preparation. 
I soon found that the warp alone was colored, and as this 
was treated with isinglass, it appeared to me that the me- 
tallic matter was employed in the latter substance. Ex- 
periment confirmed my anticipation, for I discovered oxide 
of lead and a very little oxide of copper, not only in the 
sizing in the state in which it was employed, but likewise 
in the size itself from which this was prepared. 
The proportion of the oxide of lead was so great, that 
the water in which the size was dissolved became strongly 
