.35 
When working with 50cc. of liquid,, so small a quantity 
as O’o ingm. of copper, or 1 mgm, of lead per litre, may he 
estimated by this process. If it is required to estimate 
smaller quantities than these, the liquid must be con- 
centrated by evaporation. If the amount of copper exceed 
20 mgm., or of lead exceed 10 mgm. per litre, a smaller 
quantity of the liquid than 50cc. must be used. 
“On Certain Circumstances which afiect the Purity of 
Water supplied for Domestic Purposes,” by M. M. Patti- 
SON Muie, F.P.S.E., Assistant Lecturer on Chemistry, 
Owens College. 
Water as supplied for domestic use may suffer contamina- 
tion from various sources. Those which I propose to con- 
sider are (1) the metallic pi])es through which the water 
hows, and the metallic vessels in which it may be stored, 
(2) certain of the metallic vessels through which the water 
may pass during various domestic processes, and (3) the 
existence of cisterns inside the house in which the water 
may be stored before it is used. 
The metals which are most commonly employed in the 
formation of water pipes, or of vessels in which water is 
kept, are lead and copper : these metals exert, as is well 
known, a poisonous action upon the human organism. 
It is known that water exerts a certain solvent action 
upon these metals, and that this action varies in accordance 
with the quality and quantity of the salts held in solution 
by the water. I have endeavoured to obtain a few definite 
measurements of this action in regard to (a) the nature of 
the salts in solution, (b) the quantity of those salts, and (c) 
the length of time during which the action proceeds. 
I. Action on Lead. 
A number of solutions were made containing a known 
amount of various salts dissolved in distilled water : pieces 
of clean bright lead were suspended in these liquids for 
