ON ARTIFICIAL REFRIGERATION. VZ6 



or twice, aud you Avill obtain a wasliiug- wliicli contains no ammonia; it 

 is only suiJerlicial." 



Liquid ammonia (liquor ammonia?), ortlie aqueous solution of annnonia 

 of commerce contains varying quantities of ammonia in Avater, according 

 to temperature. A mean usually stated is that water dissolves 700 vol- 

 umes of the gas. At 0° C., 0.875 gramme or 1,148 cubic centimeters of 

 ammonia gas are absorbed by one gramme of water under normal pressure. 

 The avidity of the combination is attended with the evolution of heat, 

 and this fact is demonstrated by passing a current of ak through a cold 

 concentrated solution of ammonia, displacing the gas, which carries off 

 the heat of the intruded air, and the liquid falls below — lO'^, so that by 

 this method mercury may be frozen. 



At ordinary temperatures, ammonia is a transparent gas, alkaline in 

 reaction, colorless unless the air contains a little hydrocliloric acid, when 

 visible white fumes appear. Its tension at diliercnt temperatiu-es varies 

 greatly. 



The volumes of ammonia gas at diiferent temperatures are, according 

 to Andreeff, as foUows : 



Temperature 10° C. 0° C. + 10° C. + 20o C. 



Volume 0.09805 1.000 1.0215 1.0150 



The coefficient of expansion between — 11 o and 0° C. is, according to the 

 mean of three observations by Jolly, 0.00155 ; so that at temperatures 

 sufficiently removed from its boiling-iioint ammonia expands more than 

 a gas. 



At —38.5, according to Eeguault, or at — 35o.7, according to Loir and 

 Driou, ammonia is liquid at atmospheric pressure. By a mixture of 

 chloride of calcium aud ice Guyton de Morveau condensed ammonia into 

 ahquid at —52° C, and Bunsen at —40° C. Guyton de Morveau's original 

 experiment, in which he liquefied ammonia at —21^* C., shows the iulluence 

 of an admixture of water in changing the proi^erties of ammonia, an 

 influence which Ch. Tellier had discovered when he recommended and 

 patented the liquefaction by pressure of anhydrous ammonia in ice- 

 machines. 



The specific gravity of the liquefied anhydrous ammonia is 0.7G, and 

 it is a colorless, very mobile liquid, refracting light more powerfully than 

 water. 



Faraday solidified it at —103° Fahr., when its vapor tension was still 5 

 pounds to the square inch. 



The pressures and temperatures at which ammonia gas, dried by chlo- 

 ride of calcium or fused caustic potash, could alone be liquefied, led to the 

 idea, until Tellier dispelled it, that for the purposes of artificial refrigera- 

 tion it could only be used with* water. Prof. F. A. P. Barnard, of IsTew 

 York, one of the commissioners at the Paris LTuiversal Exposition of 

 1807, wrote in the report I have elsewhere quoted a very clear aud def- 

 inite statement of the views then entertained. M. Tellier's patent was 

 in the secret archives of the French ijatent-office, and indeed the dififi- 



