ON ARTIFICIAL REFRIGERATION. 



933 



W^r^ rirs?^ ., 



terferes witli the efficiency of the maeliines. Tliey have been useful in 

 temperate climates, but have failed almost universally in those liotter 

 countries where their immense value was anticipated as a certainty. ' 



Carre's intermittent ammonia apparatus has been described in the 

 fewest possible words by Messrs. Eoscoe and Schorlemmer, from whose 

 book, tlirough the kindness of the Messrs. 

 Appleton, we have been favored with the 

 annexed illustration. The apparatus con- 

 sists of two strong iron vessels connected 

 by a vent-pipe of the same metal. The 

 cylinder (A) contains water saturated with 

 ammonia gas at 0°. When it is desired 

 to procure ice, the vessel (A) containing 

 the ammonia solution is gradually heated 

 over a large gas-burner. The ammonia 

 gas is thus driven out of solution, and 

 as soon as the pressure in the interior 

 of the vessel exceeds that of seven atmospheres it condenses iii the 

 double-walled receiver (B). When the greater portion of the gas has 

 thus been driven out of the water, the apparatus is reversed, the retort 

 (A) being cooled in a stream of cold water, whilst the liquid which it is 

 desired to freeze is placed in the cylinder (D), x)laced in the interior por- 

 tion (E) of the hollow cylinder. A reabsorption of the ammonia by the 

 water now takes place, and a consequent evaporation of the liquefied 

 ammonia in the receiver. This evaporation is accompanied by the ab- 

 sorption of heat which becomes latent in the gas. Thus the receiver is 

 soon cooled down far below the freezing-point, and the liquid contained 

 In the vessel (D) is frozen. 



Messrs. Alexander Carnegie Kirk and George Thomas Beilby, of Scot- 

 land, obtained provisional protection, but afterwards abandoned their 

 invention, which consisted essentially in placing a suital>le solid sub- 

 stance in the absorbing- vessel instead of a liquid, as heretofore employed, 

 for the purpose of absorbing the vaporized ammonia. The absorbent 

 may consist of charcoal, or of chloride of silver, or of chloride of calcium, 

 or of any solid substance having, like these, properties of absorbing large 

 quantities of vaporize<l ammonia at ordinary temperatures and of gi"s4ng 

 oft' such ammonia again when heated to an extent short of fusing the 

 said solid substance. 



In order to prepare the apparatus for a fresh operation the absorbing- 

 vessel is subjected to a sufficient heat in any convenient way; the evap- 

 orating- vessel being then kept cool, the ammonia is, by the heat, di'iven 

 from the absorbing-vessel and is liquefied in the evaporating- vessel ; the 

 absorbing- vessel is next cooled and reabsorption takes place in it, whilst 

 the anunonia is evaporated in the other A^essel and produces the cold 

 desired. Both the ammonia and the absorbent employed must be as free 

 from water as possible. 



