272 Mr. Keir’s Experiments on 
acid, when brought to the proper flrength, was capable of 
freezing with lefs cold than water does, I immerfed feveral 
acids of different ftrengths in melting fnow, in fie ad of expo- 
ling them to the air, the temperature of which was variable, 
whereas that of melting fnow was conftant and determinate. 
Thofe acids which would not freeze in melting fnow, were 
afterwards immerfed in a mixture of fnow, water, and com- 
mon fait, the temperature of which was not fo conilant and 
determinate as that of melting fnow ; but it generally remained 
for feveral hours at about 18 0 , and was fometimes feveral degrees 
lower. The intention of adding water to the fnow and fait 
was to lelfen the intenfity of the cold of this mixture, and to 
render it more permanent than if the fnow and fait alone were 
mixed. 
The acids which had frozen in melting fnow, and which 
were five in number, having been thaw r ed and brought to the 
temperature of 6o°, were found on examination to have the 
following fpecific gravities. 
1786 
1784 
1780 
1778 
1775 
Thole acids which would not freeze in melting fnow, but 
which froze when immerfed in fnow, water, and fait, having 
been expofed to a greater cold, were of a greater latitude of 
denfity. Their fpecific gravities, when brought to the tempera- 
ture of 6o°, were found to be exprelfed by the following 
numbers. 
1 804 
1814 
1810 
