the Point of Congelation . 289 
thereby is didinguilhed from the proper ice of the folution, 
which it otherwife much refembles in appearance. It is com- 
pofed principally of the depofited fait, in very minute cryftals 
like powder, invifcated and kept together with a little ice. 
Though fal ammoniac forms a tolerably tranfparent folu- 
tion, yet I perceive that in thefe experiments it was in few in- 
dances cooled much below its freezing point ; the mod: was 
nine degrees. I believe this to have been accidental, from no « 
particular attention being now bellowed on that object. 
The fal ammoniac, mixed with fnow, produced a cold of 
from 4 0 to 4°f of Fahrenheit’s fcale. 
Of all the folutions fubmitted to thefe experiments, there: 
were none more tranfparent and elegant than thofe made with 
Rochelle fait. The water diffolved a large proportion of this 
fubfhnce, and had its freezing point funk according to the 
following table. 
Rochelle fait. 
Proportion 
Freezing 
Freezing point 
tf water to 
point by the 
by calculation. 
the fait. 
experiments, 
10 : 1 
291 
O 
29J 
5 : 1 
271 
zji 
4 * 1 
261 
26 j 
2,6 : 1 
24 
2 3 i 
2,25 : 1 
22§ 
22| 
2 : 1 
21 
21 
3,6 : 1 
24 
fait depofited 
The third column is calcu- 
lated from the lad: experi- 
ment but one, in which 
the freezing point of a folu- 
tion of one part of the 
Rochelle fait in two parts of 
water proved to be 21 0 . 
All the folutions 
of Rochelle ialt bore to be cooled remarka- 
bly well. In one indance the liquor funk 1 1 § degrees below 
1 its 
