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XIII. An Account of Experiments made by Mr, John M c Nab, 
at Albany Fort, Hudfon’s Bay, relative to the Freezing of 
Nitrous and Vitriolic Acids, By Henry Cavendifh, Efj, 
F. R. S. and A, S, 
Read February 28, 1788. 
F ROM the experiments made by Mr. M c Nab, of which 
I gave an account in the LXXVIth Volume of the 
Philofophical Tranfa&ions, p. 241. it appeared, that fpirit of 
nitre was fubjedf, not only to what I call the aqueous conge- 
lation, namely, that in which it is chiefly, and perhaps in- 
tirely, the watery part which freezes, but alfo to another 
kind, in which the acid itfelf freezes, and which I call the 
fpirituous congelation. When its ftrength is fuch as not to 
diflblve fo much as weight of marble, or when its 
ftrength is lefs than ,243, as I call it for fhortnefs, it is liable 
to the aqueous congelation folely ; and it is only in greater 
ftrengths that the fpirituous congelation can take place. This 
feems to be performed with the leaft degree of cold when the 
ftrength is ,411, in which cafe the freezing point is at — i°f # 
When the acid is either ftronger or weaker, it requires a 
greater degree of cold ; and in both cafes the frozen part feems 
to approach nearer to the ftrength of ,411 than the unfrozen 
part. The freezing points, anfwering to different degrees of 
ftrength, feemed to be as follows. 
Strength. 
