68 
ON WHITE LEAD. 
ntroducing a very small portion of vapor of vinegar" with 
the gases, a superior article is at once obtained perfectly free 
from color. 
Before passing to a consideration of the principles involved 
in the above processes, we may be allowed to remark, 1st. 
That by a comparison of the dates of the 2d and 4th patents, 
it is clear that it would be very advisable for patentees to ex- 
amine previous patents on the same subject, before they lay 
open their patent to legal attacks and flaws. 2d. That by 
comparing the 3d patent with the first two, it is evident that 
a vast amount of capital might be saved by first ascertaining 
what results others have obtained before we enter the same 
field of research. 3d. That the 4th patent shows that to give 
a clear scientific view of a chemical process, something more 
is requisite than a superficial knowledge of the science, for in 
the patentee's first project, he calls the compound produced 
by attrition of lead a suboxide, and in the amended project he 
is constrained " to disclaim the opinion, that plumbicpulp, un- 
der any circumstances, can be considered a definite compound, 
and much less an oxide; but that it is a compound of lead, into 
which the elements, hydrogen, carbon and nitrogen enter, as 
well as oxygen." Neither of these views being correct, it 
would have been better to have avoided such theoretic ex- 
pressions altogether. 
Bonsdorf* exposed a clear surface of lead to moist air, which 
soon coated it with suboxide. A similar piece of lead, laid in 
pure water containing air, soon began to form a cloud of hy- 
drated oxide of lead which dissolved in the water. The 
smallest quantity of foreign matter, particularly of a saline na- 
ture, except nitrates, prevents this action; and so delicate is 
the test that Bonsdorf thinks it may be employed to try the 
purity of water, by throwing filings of metallic lead on the 
surface and observing a lew minutes whether the small cloud 
of hydrate appears; which only occurs when the water is 
pure. This fact shows why the first project of the fourth 
patent could not be successful, by introducing a carbonated 
*Berzelius Jahresbericht, 1837. 
