9 
proportionately greater in the case of those salts (nitrates, &c.) 
which aid the solvent action, than of those which tend to stop 
the solvent action of water Vipon lead. This increase is also 
gTeater for equal time-intervals, when a large surface of 
liquid is exposed to the surrounding air than when a small 
surface is so exposed. The increase was not very marked 
when the experiments were conducted in flasks through 
which a stream' of air was constantly passed. 
The exception which I have made in fawour of potassium 
carbonate, when laying down the general rule that increase 
of duration of action increases the quantity of lead dissolved, 
requires explanation. On examining the actual numbers 
obtained it is evident that the amount of lead dissolved by 
liquids which contained potassium carbonate did increase 
as the action proceeded, up to a certain point : this increase 
was however very slight and after the expiry of 340 hours 
it ceased. Hence I conclude provisionally that in the pre- 
sence of this salt the solvent action of water upon lead 
soon — comparatively speaking — reaches a maximum. I 
intend to investigate this subject more fully in a future 
communication. 
8. In conclusion, it appears to be shown by these experi- 
ments that the solvent action of dilute saline solution upon 
lead tends to attain a maximum when large surfaces of 
liquid are exposed to the surrounding air, and when the 
volume of liquid is large in proportion to the surface of lead 
exposed. Further, that under these conditions, and in the 
presence of those salts which aid the action — especially 
nitrates and more especially ammonium nitrate — the quantity 
of lead dissolved increases in an increasing ratio with the 
time during which the action is allowed to proceed. 
Mam^ experiments must however be yet carried out be- 
fore I can permit myself to generalise with safety, and these 
experiments must be conducted on a larger scale before the 
results obtained can be applied to the actual conditions 
