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ON THE EXISTENCE OF A MINIMUM VOLUME IN SOLUTION. 
By LeRoy D. Weld. 
This research has for its general object to inquire into the physical 
condition of substances in near-saturated aqueous solution. 
The subject was attacked by means of experiments at different tem- 
peratures on the apparent specific volume in solution; by which is meant, 
the volume of that amount of solution which contains one gram of the 
solute, minus the natural volume of the water contained therein. This 
quantity is always somewhat less than the volume of the solid solute. 
The experiments were made upon the sparingly soluble salt, potassium 
chlorate, dissolved in water at ordinary temperatures, by means of a 
specially designed pyknometer and thermostatic apparatus, and by em- 
ploying special precautions against errors due to evaporation, unequal 
heating of the balance, etc. 
The results are of surprising interest, as they clearly indicate the 
existence of a minimum specific volume (maximum density) in the dis- 
solved substance itself, in the near vicinity of the saturation point, 
which is very strongly suggestive of the maximum density of water 
just above its freezing point. The minimum volume of the potassium 
chlorate occurs slightly below its saturation temperature, that is, when 
slightly supersaturated; this is attributed to the presence of the water, 
just as the presence of a solute in water may bring the minimum volume 
temperature of the latter down below freezing, the impure water being 
then supercooled. The greater the amount of water present, the far- 
ther is the minimum specific volume point of the dissolved potassium 
chlorate found to be below the saturation temperature, which is also 
in agreement with the behavior of impure water. Special observations 
were made to detect the slightest trace of crystallization in the super- 
saturated solution, without success; while, to account for the results 
on this supposition, it would be necessary to assume that fully one- 
fourth of the chlorate had crystallized. The writer believes these re- 
sults indicate a true minimum volume, analogous in all respects to that 
of water at four degrees centigrade. 
Further experiments are in progress, and it is expected that a detailed 
account of the work will be duly published in the proceedings of the 
American Physical Society. 
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