OE WHITE LEAD. 
71 
ployed. If this point be attained, the question may again be 
asked whether body can be given to the compound, and 
whether it can be thus made destitute of a crystalline struc- 
ture, for in the experiments of Bonsdorf, given above, the ve- 
getation evinced a strong tendency to crystallization, and it 
appears that the same objection is generally urged against 
white lead made by attrition, viz.: it is deficient in body. 
If the theory advanced in the fifth patent (Jour. Frank. 
Inst., vol. xxvi, p. 123,) be correct, that the white lead formed 
by attrition, where carbonic acid is presented to oxide of lead 
in its nascent state, is possessed of a body and of a good co- 
lor, then we may hope that the process of attrition may yet 
be productive of good results. It should not be forgotten, 
however, that in all these processes carbonic acid is really 
present and in considerable quantity, if we suppose a large 
amount of air to pass over the agitated lead, but then the 
quantity relatively to the oxygen of the atmosphere is very 
small. I would suggest whether it would not be desirable to 
perform an experiment in a similar manner to the above, in 
which water may be omitted and due proportions of air and 
carbonic acid driven through an agitated apparatus containing 
simply moistened lead, either without, or, perhaps, better 
with the aid of steam, or at a higher than the ordinary at- 
mospheric temperatures. 
II. Processes more or less dependent on Single Elective 
Affinity. — These processes all depend upon the decomposi- 
tion of a subsalt of lead by carbonic acid. 1. Thenard made 
the first suggestion relative to the principle, and MM. 
Brechoz and Leseur, who arranged the contrivances for con- 
ducting the process, received a prize for their white lead. 
Neutral acetate of lead was digested with litharge forming a 
soluble subacetate, through which, diluted with water, was 
passed a stream of carbonic acid. Carbonate of lead precipi- 
tated, and there remained a neutral acetate in solution, which 
being redigested with litharge, again formed a subsalt, and 
was again precipitated as before. Thus the acetate of lead 
first employed was constantly used in the operation, a small 
