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IOWA ACADEMY OP SCIENCE 
4. Barium Chloride — Water (per cent) 
After grinding two hours 17.06 
The unground crystals 14.95 
The grinding increased the amount of water 2.11 
This result was unlooked for but repeated trials showed the^^-same 
increase. While at first the substance seemed dry, by continued grinding 
it became moist and sticky. 
5. Copper Sulphate — Water (per cent) 
The unground crystals 35.88 
After two hours’ grinding 34.95 
Removed by grinding 0.93 
The substance changed from a bright blue to almost white in the 
grinding process. In both cases heat was applied very carefully to 
prevent the decomposition of the copper sulphate. 
6. Ammonium Alum — Water (per cent) 
The unground crystals ' 47.29 
After two hours’ grinding 46.96 
Removed by grinding 0.33 
The substance was difficult to grind toward the end of the operation 
as it would harden to the mortar from which it was difficult to be 
removed. This was most easily effected with a platinum spatula.* 
7. Sodium Alum — Water (per cent) 
The unground crystals 37.89 
After two hours’ grinding 23.84 
Removed by grinding 14.05 
The result was surprising, but three trials showed the same large dif- 
ference. 
8. Iron Alum — (Water (per cent) 
The unground crystals 41.24 
After two hours’ grinding ’. 29.84 
Removed by grinding 11.40 
The substance became so firmly attached to the mortar that it could 
be removed only with a platinum spatula. 
9. Iron Sulphate — Water (per cent) 
Unground crystals 38.64 
After two hours’ grinding 24.63 
Removed by grinding 
14.01 
