IOWA ACADEMY OP SCIENCE 
133 
THE EFFECT OP CONTINUED GRINDING ON WATER OP 
CRYSTALLIZATION. 
(Second Paper.) 
BY NICHOLAS KNIGHT. * 
In the proceedings of the “Iowa Academy of Science,” XVII, 131, we described 
a series of experiments to show the effect of long grinding on water of 
crystallization. Some of the results were rather surprising, and we decided 
to repeat the work, and also to include a larger number of hydrates in the experi- 
ments. The conditions under which the work was done were as uniform as 
possible. After grinding, the specimens were kept from the air in ground 
glass stoppered bottles of about 20 c.c. capacity. Gram portions were weighed 
out for all determinations. In finding the water content of the unground 
specimens, the coarse crystals were merely crushed, and the fine crystals 
were used without further division. Usually about three grams were taken 
for the grinding, which was effected in a large highly polished agate mortar. 
The grinding was continued for two. hours. In some cases it might be hard 
to decide whether the loss of water is due to efflorescence or to the heat caused 
by the continual grinding. Both causes doubtless contributed to some of the 
results. 
In our work on barium chloride, the chemically pure products of two manu- 
acturers were used. The sample was taken from the original package, and 
the amount of water determined, and another portion was ground two hours, 
and the water content estimated in the same way. The two specimens were 
then crystallized once from water, and coarse and fine crystals were obtained. 
They were dried between filter-papers and at once placed in the glass stoppered 
bottles. The water was determined as in the original specimens. The results 
are as follows: 
kahlbahm’s. 
Unground 
Ground . 
Loss 
Unground 
Ground . 
Loss 
-Crystals- 
Per cent. 
Coarse (percent) Pine (percent) 
. 15.03 
14.86 
14.84 
. 14.79 
14.80 
14.80 
. 0.24 
0.06 
0.04 
MERCK’S. 
. 14.89 
14.78 
14.78 
. 14.38 
14.74 
14.77 
. 0.51 
0.04 
0.01 
It will be noticed that the loss is greater in the original substance than after 
one crystallization from water. It is also greater in the coarse than in the fine 
