858 W. A. Norton—Force of Hiffective Molecular Action. 
to be 81°C. At this temperature then the molecular curve for 
this gas was the curve for which k=4°7. 
e have already seen that when a liquid reaches its boiling 
point in vacuo, its molecular curve is just tangent to the axis, 
x, at the point s=2°84r, and that k=4°934. When the liquid, 
say water, is subject to the atmospheric pressure, as the tem- 
perature rises above 72° F., (its boiling point in vacuo) and m 
continually increases, the curve subsides until the molecular 
repulsion, for e=8r, is just on the point of prevailing over 
the atmospheric pressure. The liquid will then be at its 
boiling point, 212° F. Theslightest increase of heat repulsion 
will now cause the molecules to recede from each other, since 
the effective repulsive ordinates augment with the distance, 2, 
and this recess should continue until the repulsive ordinate 
again becomes equal to the minimum value, that obtained 
when the recess began. ‘To this tendency to a sudden separa- 
tion of the molecules over a wide range of distance may be 
ascribed the agitation of the liquid, called boiling; and the 
amount of the final separation should fix the ratio of expansion 
in the passage of the liquid into vapor, at the boiling point. If 
the liquid boils under a higher pressure than one atmosphere, 
the access of heat augments the minimum molecular repulsion 
that obtains at about the distance 37, until it is on the point of 
prevailing over the actual pressure. The curve will now have 
the molecular curve, both by diminishing »(=) the unit in 
terms of which the repulsions are expressed, and increasing the 
ratio k{ =— }. 
™m 
: [To be continued. ] 
