206 E. M. Walton—Liquefuction and Cold produced 
ART: XXXUML—Liquefaction and Cold produced by the mutual 
reaction of Solid Substances; by Miss EVELYN M. WALTON, 
THE mixing of two dry, finely-powdered salts, one or both 
containing water of crystallization, is often attended by lique- 
faction with decrease of temperature which in many instances is 
very marked ; and sometimes there is also a decided change in 
color. 
that of a stiff paste. 
History.—It has long been known that freezing-mixtures 
may be made by mixing some salt with ice or snow, and 1 
1875-6 Guthrie* determined the lowest attainable temperature 
of quite a large number of such mixtures... 
e found that the lowest temperature obtained with any 
given salt was the same whatever its initial temperature; also 
that within certain wide limits this was independent of the pro- 
portions used. 
The earliest allusion I find made to freezing-mixtures, 
formed by the use of salts only, is in the ninth volumet of this 
Journal, where Ordway, in a paper on Nitrates, mentions 
experiments in which the mixture of ammonium bicarbonate 
with hydrated iron nitrate and with hydrated aluminum nitrate 
was followed by a reduction of temperature from 58° to —5° F., 
and from 51° to —10° respectively. Subsequently} he mixed 
nitrate of iron with Glauber’s salt and obtained a reduction of 
32° Fahr, 
Berthelot, in his recent work on Thermo-Chemistry, devotes 
a brief space to the subject, and the Comptes Rendus, vol. X¢; 
pp. 1163, 1282, contains a communication from Ditte calling 
attention to this wonderful phenomenon. He considers the 
use of concentrated acids with hydrated salts, also mixtures 
composed solely of salts. An example is given of ammonium 
nitrate and hydrated sodium sulphate mixed together 1m @ 
mortar, the loss of heat being about 20° C. 
Liquefaction of Salts.—As far as we know, when any salt sol- 
uble in water is mixed with ice liquefaction is sure to follow, 
and the minimum temperature is below 0° C. But, when salts 
only are taken, the case is different. : 
n some instances liquefaction is very evident, 10 other 
there is none at all, and in still others it is doubtful ; while the 
* Phil. Mag., xxix, 314. + IL, ix, pp. 30,31, 33. IL, xxvii, p. 15 
