Experiments on freezing Mixture si $4^ 
another bottle, and fend both home to be examined, as it 
would thereby be known, whether it was the whole acid, or 
only the watery part, which froze, For the fame purpofe alfo I 
fent fome dephlogiflicated fpirit of nitre of the fame ftrength* 
and alfo fome ftrong oil of vitriol. I alfo fent fome fpirit of 
nitre and fpirit of wine, both diluted with fo much water, that 
it was expected, that with the cold of Hudfon’s Bay they 
would fuffer the firft kind of congelation ; that is, their wa- 
tery part would freeze, and thereby make the difference between 
the two kinds of freezing more apparent. 
3. In the fame Paper I fay, 66 That on adding fnow gra- 
u dually to fome of the fpirit of nitre ufed by Mr. Hutchins, 
44 I found, that the addition of a fmall quantity produced heat 
44 inftead of cold ; and it was not until fo much was added as to 
44 increafe the heat from 28° to 51 0 , that the addition of more 
44 fnow began to produce cold ; the quantity of fnow required 
16 for this purpofe being pretty exadtly one quarter of the 
44 weight of the fpirit of nitre, and the heat of the fnow and 
u air of the room, as well as the acid, being 28°. The reafon 
44 of this is, that a great deal of heat is produced by mixing 
44 water with fpirit of nitre, and the ftronger the fpirit is, the 
44 greater is the heat produced. Now it appears from this 
46 experiment, that before the acid was diluted, the heat 
44 produced by its union with the water formed from the melted 
44 fnow was greater than the cold produced by the melting of 
44 the fnowj and it was not till it was diluted by the addition 
46 of one quarter of its weight of that fubftance, that the cold 
46 generated by the latte? caufe began to exceed the heat gene- 
44 rated by the forme*# From what has been faid, it is evi- 
46 dent, that the cold of a freezing mixture, made with the 
undiluted acid, cannot be quite io great as that made with 
I i 2 " the 
