HEAT. 



they act upon each other. To illustrate 

 the necessity of this precaution, it may 

 be mentioned, that snow and common 

 salt have no action upon one another 

 when mixed at the temperature of 1 

 of Fahrenheit. 



Messrs. Allen and Pepys solidified 

 56 pounds of quicksilver by the use of 

 1 3 pounds of muriate of lime, and the 

 same weight of snow. The whole of 

 these were not mixed at once, as one 

 proportion was expended in cooling the 

 other. 



To succeed with the experiment upon 

 a small scale, a few ounces of mercury 

 in a thin glass retort may be exposed 

 to a mixture of one pound of crystal- 

 lized muriate of lime, with the same 

 quantity of snow : when this mixture 

 ceases to reduce the temperature, ano- 

 ther similar one should be used, which 

 seldom fails to effect congelation. 



Dr. Henry recommends the appa- 

 ratus represented in section, (fig. 24.) 



Fig. 24. 



The outer vessel a a, he directs ta 

 be of wood, about \1\ inches square 

 and 7 inches deep. It should have a 

 wooden cover, rabbeted in, and fur- 

 nished with a handle. Within this is 

 placed a* tin vessel b, standing on 

 feet which are 1 in. high, and having 

 a projection at the top half an inch 

 broad and an inch deep, on which 

 rests a shallow tin pan c. Within the 

 second vessel is a third, d, made of un- 

 tinned iron, and supported by feet two 

 inches high : this vessel is four inches 

 square, and is intended to contain the 

 mercury. When the apparatus is used, 

 a mixture of muriate of lime and snow 

 is put into the outer vessel a a, so as 

 completely to surround the middle ves- 

 sel b b. Into the latter the vessel d, 

 containing the quicksilver to be frozen, 

 previously cooled down by a freezing 

 mixture, is put ; and this is immediately 

 surrounded by a mixture of snow and 

 muriate of lime, previously cooled to 

 of Fahrenheit, by an artificial mixture 

 of snow and common salt. The pan c 

 is also filled with these materials, and 

 the wooden cover is then put in its 

 place. The vessels are now left till the 

 quicksilver is frozen. The solution of 

 muriate of lime may be evaporated, and 

 the salt crystallized for future experi- 

 ments. Henry's Chemistry, vol. i. p. 

 94, and description of plate 4. 



The following Tables exhibit a col- who made a great many experiments 

 lective .view of all the frigorific mix- upon the artificial production of cold. _, 

 tures in the publication of Mr. Walker, 



TABLE, consisting of Frigorific mixtures having the power of generating or 

 creating cold without the aid of ice, sufficient for all useful and philosophi- 

 cal purposes in any part of the world at any season. 



FRIGORIFIC MIXTURES WITHOUT ICE. 



MIXTURES. Thermometer Sinks. 



PARTS. 



. 5 



Degree of 



Cold 

 produced. 



Muriate of Ammonia 



Nitrate of Potash 5 



Water 16 



Muriate of Ammonia 5 



Nitrate of Potash 5 



Sulphate of Soda 8 



Water 16 



Nitrate of Ammonia 1 



Water 1 



Nitrate of Ammonia 1 



Carbonate of Soda 



Water . . 



From +50 5 to +10 40 



i} 



H-50 to + 4 



4-50 to + 4 



-f 50 to - 7 



46 



46 



.57 



