ON ICE-MAKING AND ICE-MACHINES. 



ID 



of the blocks were five weeks old. We have an 

 apparent paradox in the fact that the combustion 

 of one ton of coal in the furnace-fires will produce 

 eight tons of ice. 



In the last number 1 of the Popular Science 

 Review it was found necessary to refer to the 

 researches of Faraday and others on the liquefac- 

 tion of gases, and of Prof. Andrews on the con- 

 tinuity of the liquid and gaseous states of matter ; 

 it is therefore of great interest to note how a 

 purely scientific fact can in a most unexpected 

 way be made available for industrial purposes. 

 No one could have imagined that the liquefaction 

 of gases could prove of any practical benefit to 

 mankind, but we now know that such is the case, 

 since M. Carre's ammonia freezing-machine de- 

 pends upon the liquefaction of the gas by press- 

 ure, and its subsequent condensation in water 

 after it has produced a low temperature by its 

 evaporation. The operation is conducted with- 

 out the application of any mechanical power. A 

 hollow conical condenser of iron has a space be- 

 tween its inner and outer surfaces, which is con- 

 nected by a tube with a boiler containing ordi- 

 nary liquid ammonia ; that is to say, a solution 

 of about seven hundred volumes of ammoniacal 

 gas in one volume of water. The conical con- 

 denser is immersed in a stream of cold water, 

 while the boiler is heated over a fire or large gas- 

 burner to a temperature of 2*70° Fahr. During 

 this operation the ammoniacal gas is expelled 

 from the water, and is condensed by the pressure 

 of its own particles and the cooling action of the 

 stream of water. If, now, fresh cold water be 

 placed in the condenser-cone, and the heated 

 boiler be cooled in water, the ammonia distills off 

 at the expense of the heat in the water to be 

 frozen, and finds its way back once more to the 

 boiler, ready for another operation. 



Leslie's famous experiment of causing water 

 to be frozen by the rapid absorption of heat 

 caused by its own evaporation has been modified 

 by M. Carre, in such a manner that ice in small 

 quantities, as, for instance, in water-bottles, may 

 be made in a few minutes. The apparatus cou- 

 aists of an air-pump, to which the water-bottle 

 is attached. As the handle of the pump is worked 

 and the air exhausted, a quantity of oil of vitriol 

 is agitated in a vessel, through which all aqueous 

 vapor and air from the water-bottle must be 

 drawn. The avidity with which the oil of vitriol 

 absorbs the vapor as fast as it is formed so hast- 

 ens the evaporation that in a few minutes a bot- 

 tle of ice is the result. 



1 See " Mineral Cavities and their Contents." 



Perhaps, of all machines, the one of most in- 

 terest is that invented by M. Raoul Pictet, of 

 Geneva, the striking feature in which is the em- 

 ployment of liquefied sulphurous acid as the ab- 

 sorbent of heat instead of ether. In all other 

 machines there is a liability to a slight leakage, 

 on account of the fact that the cylinder of the 

 exhausting and condensing pump is kept air- 

 tight to some extent by the lubricating material. 

 Now, as ether and all kinds of grease are solvents 

 of each other, it is easy to account for a certain 

 amount of escape, which will be difficult to avoid. 

 Liquefied sulphurous acid does not dissolve to 

 any considerable extent in oil, and when free 

 from moisture is without action on metals ; and, 

 although it might be expected that the packing 

 of the piston might in time be acted on by sul- 

 phurous acid, yet this danger has. been entirely 

 obviated by the use of manufactured asbestos- 

 packing, which is now being greatly used for 

 high-pressure steam-engines. 



When required to work in hot climates, the 

 ice-making machines most generally in use are 

 open to serious objections, and grave inconven- 

 iences are experienced in their constant employ- 

 ment. Thus, amnioniacal machines work at a 

 pressure of twenty atmospheres, with water at 

 80° Fahr., and are thus liable to leakage, or even 

 to the danger of an explosion. Methylated ether 

 machines are open to the same objection, in ad- 

 dition to which there is a danger of fire when a 

 leakage occurs, which unfits them for use at sea. 



Now, in the use of sulphurous acid there is 

 the great advantage that at 80° Fahr. its tension 

 does not exceed four atmospheres, while it may 

 be liquefied at 25°, and its tension then is only 

 equal to the pressure of the atmosphere. It has 

 no action upon metals when kept free from water; 

 and, in order to obtain it in a perfectly anhydrous 

 condition, M. Pictet prepares it by the action of 

 heat on a mixture of oil of vitriol and sulphur, 

 the gas being dried by oil of vitriol. The con- 

 densing and refrigerating apparatus consists of 

 tubular vessels similar to those employed with 

 other liquids, such as ether. 



One of these machines is daily at work at the 

 Chelsea Ice-Rink, and is capable of making forty 

 tons of ice per day. The skating-floor, which is 

 the invention of Mr. John Gamgee, consists of a 

 number of flattened metallic tubes placed side by 

 side on a bed of concrete or asphalt ; the inte- 

 rior of the tubes is kept filled with an uncongeal- 

 able mixture of glycerine and water, which is al- 

 lowed to flow in from an elevated cistern. Clear 

 ice is secured by coating the tubes with water- 



