258 Mr. Cavendih’s Account of fome 
freezing; and confequently, as this heat Was found to coincide 
very nearly with the freezing point of thefe acids, after dilu- 
tion, it follows that their ftrengths at that time could differ 
very little from the ftrength of eafieft freezing. 
If the temperature of the.liquors at the beginning of the experi- 
ment had been above the point of eafieft freezing, none of the acid 
would have congealed during the dilution, and nothing could 
have been learnt from the experiment relating to the point of ea- 
fieft freezing ; but the heat would have kept increafing, till the 
acid was diluted to that degree of ftrength at which the cold pro- 
duced by the difiolving of the fnow was juft equal to the heat 
produced by the union of the melted fnow with the acid*; 
after which the addition of more fnow would begin to produce 
cold. When I recommended this method of finding the beft 
ftrength of fpirit of nitre for producing cold, by the addition 
of fnow, I was not aware of any impediment from the freez- 
ing of the acid, in which cafe it would have been a very pro- 
per method ; but on account of this circumftance it can hardly 
be confidered as fuch, except when the cold of the acid at fiet- 
ting out is lefs than that of eafieft freezing. 
In the dephlogifticated fpirit of nitre the freezing points 
anfwering to the ftrength of ,434, ,53, and ,56, were faid to 
be - 4°|, — 1 9 0 , and - 30° ; and the differences of - 30° and 
— 1 9 0 from ~4°1 are to each other very nearly in the 
duplicate ratio of ,126 and ,096, the differences of the cor- 
refponding ftrengths from ,434; which, as ,4341s the ftrength 
of eafieft freezing, is the proportion that might naturally be 
* In the experiment related in my observations on Mr. Hutchins’s Experi- 
ments, this ftrength was rather greater than that of eafieft freezing : but whether 
it is fo in degrees of cold exceeding that in which my experiment was tried, does 
not appc ar. 
4 expelled, 
