THE EFFECT OF CONTINUED GRINDING ON WATER OF 
CRYSTALLIZATION. 
BY NICHOLAS KNIGHT. 
Mauzelius (Sveriges Geol. Under soekning Arsbok 1 1907) ; Day and 
Allen (Bull. U. S. Geol. Survey, 305, p. 35), Hillebrand (Journ. Am. 
Cliem. Soc. xxx 7) and Knigbt (Chem. News xcvii 122) have shown the 
effect of fine grinding on the water and ferrous content of minerals and 
rocks. In this paper we are able to show the effect of continued grind- 
ing on some hydrates. . The water was determined in each specimen after 
grinding it a half hour, an hour, an hour and a half, and two hours 
The two hours’ grinding seemed to give the maximum results. The 
grinding was done by hand in an ordinary Wedgewood mortar. In each 
.determination, exactly one gram of the substance was weighed into a 
porcelain crucible and the water was removed by heating to constant 
weight with a Tirrell burner. For purposes of comparison, the water 
was first determined in the unground specimens. All the conditions 
were maintained as nearly uniform as possible. 
1. Magnesium Sulphate — Water (per cent) 
The unground crystals 51.85 
After two hours’ grinding 49.30 
Removed by grinding . .• 2.55 
2. Sodium phosphate — Water (per cent) 
The unground crystals 58.61 
After two hours’ grinding 56.76 
Removed by grinding 1.85 
3. Potassium Alum — • ^ 
Water (per cent) 
The unground crystals 45.47 
After two hours’ grinding 44.98 
Removed by grinding 0.49 
The unground specimens swelled to such an extent that great care 
was necessary in the heating to prevent the alum from creeping over 
the walls of the crucible. After grinding to a fine powder there was 
no such difficulty, as the substance fused to a hard ball in the bottom 
of the crucible. 
