346* 
ACTION OF WATER ON LEADEN PIPES. 
parts of the scale of solutions) are carefully evaporated to 
dryness and ignited in a small porcelain capsule, to expel 
any organic matter that may have been present, moistened 
with nitric acid, and then warmed, with the addition of 
acetic acid and water, till the volume becomes 10 cub. 
centim. A drop of acetate of potash is then added, and then 
hydrosulphuric acid gas transmitted through the solution. 
A precipitate results, or it does not. If it does, to know 
its value or the amount of lead it contains, the scale is re- 
sorted to. Though it might rarely be possible to identify it 
with either one of two precipitates in the scale, there could 
be no difficulty in deciding between which two it should 
fall, or nearest to which one of two it should be placed. 
If 50 cub. centim. thus treated yielded no precipitate, 100 
cub. centim. were evaporated to dryness, and the residue 
similarly treated. If this failed, 500 cub. centim. were 
taken, and in some instances more, and the same course 
pursued. 
It was natural to suppose that the presence of foreign 
bodies, such as occur in natural waters, might embarrass 
the precipitation* This led to the preparation of a series of 
graduated solutions of lead, with all the common salts oc- 
curring in waters, from the reagents in my laboratory. 
They are similarly treated with acetate of potash, free 
acetic acid, and a stream of hydrosulphuric acid ; and 
though it was possible to see -differences in the amounts of 
the precipitates, they fell very greatly within the differences 
between the successive members of the graduated series. 
Chem. Gaz. 
