10 
which influence the mutual action of water and lead in our 
domestic water supply. 
9. By comparing the absolute quantities of lead dissolved 
as stated in the foregoing tables with those tabulated in 
former papers and obtained under somewhat comparable 
circumstances, it is apparent that the present numbers are 
much smaller than the former. This I believe to be due 
to the chemical purity of the lead itself. In former experi- 
ments I made use of ordinary sheet lead : in the present 
experiments what is sold by the chemical dealer as “ pure 
lead” was employed. I believe that many contradictory 
results noticed in the numbers obtained by different experi- 
menters on the subject of the action of water on lead can 
be traced to slight differences in the purity of the lead em- 
ployed by them. I purpose to examine this subject quanti- 
tatively, and hope on a future occasion to lay the results 
before the Society. 
