23 
Steam Engine, 
perature of water, have each a considerable portion of iin- 
combined caloric. Now, salt has a strong affinity for 
water; but the union cannot take place while the water 
continues solid. In order, therefore, to act on the salt, 
the snow absorbs all the free caloric required for its lique- 
faction ; and during this cha:nge, the free caloric, both of 
the snow and of the salt, amounting to 32 , becomes la- 
tent, and is concealed in the solution. This solution re- 
mains in a liquid state at 0, or below 0 of Fahren- 
heit ; but if a greater degree of cold be applied to it, the 
salt separates in a concrete form. 
3. Most neutral salts, also, during solution in water, 
absorb much caloric ; and the cold, thus generated, is so 
intense as to freeze water, and even to congeal mercury. 
The former experiment, however {viz. the congelation of 
water), may easily be repeated on a summer’s day. Add 
to 32 drachms of water, 11 drachms of muriate of ammo- 
nia, 10 of nitrate of potash, and 16 of sulphate of soda, 
all finely powdered. The salts may be dissolved separate- 
ly, in the order set down, A thermometer, put into the 
solution, will showq that the cold produced is at or below 
freezing; and a little water, in a thin glass tube, being im- 
mersed in the solution, will be frozen in a few minutes. 
Various other freezing mixtures lue described in Mr. 
Walker’s papers in the Philosophical Transactions for 
1787, 88, 89, 95, and 1801. Of these the table, given in 
the Appendix, for which I am indebted to the obliging 
communication of the author, contains an arranged ab- 
stract. 
4. Muriate of rune, when mixed with snow, produces 
a most intense degree of cold. This property was dis- 
covered some years ago by M. Lowdtz, of St. Petersburg, 
and has been since applied, in this country, to the conge- 
lation of mercury on a very extensive scale. The propor- 
tions which answer best, are about equal weights of 
