526 
IOWA ACADEMY OF SCIENCE Vol. XXIV, 1917 
Qi and Qo represent the molar heats of solution calculated for 
the intervals (25°-30°) and (30°-35°), respectively. 
SUMMARY. 
As might be expected, the solubility of succinic acid-increases 
with rise in temperature in all of the solvents studied. Consid- 
ering the alcohols alone, the solubility at all temperatures is 
greatest in the methyl alcohol and decreases rapidly with the in- 
crease in the molecular weight of the alcohol. Methyl, ethyl, 71 - 
propyl and n-butyl alcohols have the simple molecular chain 
structure. n-Butyl (CLI 3 CH 2 CH 2 CH 2 OH) , iso-butyl ((CH 3 )» 
CHCHoOH) and tert-butyl) ((CH 3 ) 3 COH) are isomeric com- 
pounds whose molecular structures differ simply in the grouping 
of the atoms within the molecules. The effect of these structural 
differences upon the solubility of succinic acid is to be seen from 
the table, the solubility being greatest in the tertiary-butyl and 
least in the iso-butyl alcohol. 
The effect of solvent upon the heat of solution is apparently 
just the reverse of that upon the solubility. For the normal 
alcohols the heat of solution increases as the molecular weight 
of the alcohol increases. Likewise, for the isomeric butyl alcohols 
the heat of solution is greatest in the iso-butyl and least in the 
tertiary-butvl alcohol. 
For the temperature intervals studied the heat of solution 
shows a decided increase with rise in temperature for solutions in 
water, methyl alcohol and iso-amyl alcohol. The reverse is equally 
true for solutions in iso-butvl alcohol. For the other alcohols 
the heat of solution may be considered as practically independent 
of the temperature. Obviously, the heat of solution of a given 
substance is a specific property of the solvent. These deductions 
are based entirely upon the assumption of the validity of the 
van’t, IToff isochore when applied to solubility methods. 
Hints as to interesting relations between the solubility of the 
solute and the surface tension, compressibility and the association 
of the solvent have been observed. Before any generalizations 
can be made regarding these relations the work will have to be 
extended to higher alcohols and these we do not have. 
Physical Chemistry Laboratory, 
The State University of Iowa. 
