428 F. W. Clarke— Volume of Water of Crystallization. 
I am aware that this formula gives one atmosphere more 
pressure than the water column yields; but if the reader will 
refer back to the experiments, he will find that the aspirator 
actually utilizes one atmospheric pressure more than is due to 
the water column, for high water pressures one or more atmos- 
phere, and for less powerful ones the aspirator utilizes a portion 
of an atmosphere more than is due to the column of water. - 
ART. XXXVIL—On the Molecular Volume of Water of Crystal- 
hization; by FRANK WIGGLESWORTH CLARKE, 8. B., Profes- 
sor of Chemistry and Physics in the University of Cincinnati. 
_ It is an important problem in theoretical chemistry to de- 
termine the nature of the difference between water of constitu- 
tion and water of crystallization. Some time since it occurred 
to me that perhaps a clue to the solution of this problem might 
be obtained from a careful comparison of the molecular vol- 
