Experiments on freezing Mixtures . 
26j 
On the Vitriolic Acid. 
21. On December 12, the drong oil of vitriol N° rj-i. was 
found frozen, and was nearly of the colour and confidence of 
hogs-lard. Its temperature, found by prefling the ball of a 
thermometer into it, was — 15 0 , and that of the air nearly the 
fame ; but in the night it had been expofed to a cold of - 33°. 
It diflolved but flowly on being brought into a warm room, 
and was not completely melted before it had rifen to + 20% 
and even then was not very fluid, but of a fyrupy confidence. 
During the progrefs of the melting, the congealed part funk to 
the bottom, as in fpirit of nitre ; and many air bubbles fepa- 
rated from the acid, which, when it was completely melted, 
formed a little froth on the furface. As foon as it was fuffi- 
ciently melted to admit of it, which was not till it had rifen 
to the temperature of + io°, the fluid part was decanted, and 
both were fent home to be examined. 
It is remarkable, that the frozen part did not intirely diflolve 
until the temperature was fo much increafed. This would in- 
cline one to think, that the frozen part mud; have differed in 
fome refpedd from the relt, fo as to require much lefs cold to 
make it freeze ; but yet I could not find that the drength of 
the decanted part differed fenfibly from the red. 
It appeared by another bottle of oil of vitriol, which alfo 
froze by the natural cold of the air, that this acid, as well as 
the nitrous, contracts in freezing. 
22. On December 21, when the weather was at — 30°, the 
vitriolic acid N° 103. was diluted with fnow, as directed in 
Art. 3. The fnow diflolved immediately, and no figns of 
congelation appeared during any part of the procefs. The 
temperature 
