7 
I have not tabulated the whole of the results here, 
but only those which are directly comparable with one 
another. 
6. It is scarcely admissible from these experim ents to con- 
clude that exposure to air invariably causes an increase in 
the quantity of lead dissolved. As in the consideration of 
the influence of surface exposed, it was found to be difficult 
if not impossible to eliminate other circumstances which 
modified the action, so here we appear to have many condi- 
tions tending to overshadow the effects of that one which 
it was especially desired to study. If we compare the 
quantities of lead dissolved in corked flasks and in open 
beakers, the action appears to be greater in the former than 
in the latter cases, until we come to deal with actions 
allowed to proceed during considerable periods of time, and 
upon somewhat extended surfaces of lead. When the 
surface exposed extended to 50 sq. cm. (to 500 cbc. of 
liquid) — ^and the time of action amounted to 300— -500 
hours, the exposure of the surface of liquid to a considerable 
surface of air invariably increased the quantity of lead dis- 
solved in a given time. 
In these experiments the surface of liquid exposed to the 
air was increased from about 2 to about 100 sq. cm. 
By comparing the quantities of lead dissolved in flasks or 
beakers and in open basins we find that there is invariably a 
very marked increase in the latter cases. The increase here 
also becomes more marked when the action has been allowed 
to proceed for tolerably extended periods of time. 
In these experiments the surface of liquid exposed to the 
action of air increased from about 2 to about 170 sq. cm* 
It may be that the relation between lead exposed and 
total quantity of liquid infiuences the action of the air upon 
the metal: this point I propose to examine in a further 
communication. The passage of air through the various 
liquids certainly caused an increase in the quantity of lead 
