134 
IOWA ACADEMY OP SCIENCE 
crystals. The increase in weight, and the stickiness noticed in the case of 
barium chloride in our first paper were probably due to the presence of the 
very deliquescent calcium chloride as an impurity. 
To ascertain whether it was superficial water that the grinding removed, or 
the water of crystallization, portions of one of the original specimens, and of 
the coarse and fine crystallizations, were weighed out, heated a few moments, 
and the loss of w'ater determined. The residue was then ground for two hours, 
and portions weighed out and again heated, and the loss by the grinding 
determined. The results were as follows: 
Original specimen, 14.89% water. 
Removed by first heating 
Removed by second heating 
Total 
Loss 
Purified crystals, 14.78% water. 
Removed by first heating 
Removed by second heating 
Total 
Loss 
First Second 
determination. determination, 
(percent) (percent) 
2.31 
. 14.62 
12.42 
0.26 
14.73 
14.88 
0.16 
0.01 
4.75 
14.11 
10.01 
0.68 
14.76 
14.79 
0.02 
0.01 
It requires a comparatively low temperature to remove 10 or 12 per cent of 
the water. It was also observed that the specimen in the crucible could be 
placed very near the fiame without decomposition. Results that differed from 
one another by no more than one-hundredth of a per cent were easily attain- 
able. The results with barium chloride seem to indicate that most of the 
water removed by grinding is superficial, although a small portion of the 
water of crystallization can also be removed. 
To learn the effect of the atmosphere upon barium chloride before and after 
grinding, portions of each were left in the air a few days. The unground 
specimens underwent no change, but the ground portions took up the greater 
part of the water that had been removed. The fine crystals after grinding would 
take up slightly more w^ater than the course ones. 
Removed by grinding 
(Per cent) 
Days in air 
Regained 
(Per cent) 
Kind of crystals 
0.04 
1 
0.007 
Pine 
0.04 
3 
0.03 
Pine 
0.06 
1 
0.01 
Coarse 
0.06 
3 
0.04 
Coarse 
0.24 
1 
0.06 
Uncrystallized 
0.24 
3 
0.16 
Uncrystallized 
Potassium Alum, AIK ( 804)2 I 2 H 2 O. 
Ammonium Alum, A 1 NH 4 ( 864 ) 2 . I 2 H 2 O. 
These salts require more care in heating than barium chloride as they are 
quite easily decomposed. The commercial products were purified by crystalliza- 
tion, and co<arse and fine crystals were obtained. The water was determined in. 
