Experiments on the freezing of Acids . 1 8 i 
point of oil of vitriol, anfwering to different flrengths, is 
nearly as follows : 
J 
Strength. 
Freezing point. 
>977 
O 
+ I 
,918 
— 26 
,846 
+ 42 
» 75 s 
"45 
From hence we may conclude, that oil of vitriol has not 
only a flrength of eafieft freezing, as Mr. Keir has (hewn; 
but that, at a flrength fuperior to this, it has another point of 
contrary flexure, beyond which, if the flrength be increafed, 
the cold neceffary to freeze it again begins to diminifh. 
The flrength anfwering to this latter point of contrary 
flexure muft, in all probability, be rather more than ,918, as 
the decanted or unfrozen part of N° 2. feemed rather ftronger 
than the undecanted part j and for a like reafon the flrength of 
eafielf freezing is rather more than ,846. 
Mr. Keir found that oil of vitriol froze, with the leaft degree 
of cold, when its fpecinc gravity at 6o° of heat was 1,780, 
and that the freezing point anfwering to that degree of flrength 
was +46°; which agrees pretty nearly with thefe experiments, 
as the flrength of oil of vitriol of that fpecihc gravity is ,848, 
that is, nearly the fame as that of N° 3. 
