ON ARTIFICIAL REFRIGERATION. 911 



crystals of four sides, which arc streaked parallel to the sides. By and 

 by these crystals become perfectly white and oi)aque, and a third axis of 

 crystallization is developed, which was at lirst suiJi>ressed. The crys- 

 tals are perfectly beautiful, resembling, where opaque, frosted silver. 

 On allowing a thick cup to freeze, and breaking it, an exquisite i)early 

 appearance is presented. The structure ajipears then quite fibrous, the 

 fibres running perpendicular to the axis of the cup ; and tlie appearance, 

 as far as structure is concerned, is similar to that of sublimed chloride 

 of ammonium. The temperature remains constant at —15° C, even to 

 perfect dryness," 



Shortly after my return to England from Texas, in 1869, where I felt 

 the want of a harmless antisei)tic, I was the cause of the manufacture, 

 commercially, of the chloride of aluminium. The strong solution obtained 

 by the double decomposition of chloride of calcium and suli^hate of alumina 

 absorbs water from the air with great avidity. On immersing fish in a dilute 

 solution of this chloride, a very remarkable phenomenon was observed. 

 Alumina was deposited on the surface, and h^ drochloric acid penetrated 

 the tissues, preserving them under proper management with very slight 

 adventitious flavor. 1 found that strong solutions would resist congela- 

 tion to below — 10° Fahr. Professor Guthrie found that when thrown 

 upon several times its own weight of ice, the two would liquefy, and the 

 temperatiu-e stand above 0° C. "The strongest commercial solution of 

 chloride of aluminium, however, when at the temperature of the air, or 

 at 0'^, or at 100<^ C, will reduce the temperature to — 13° C. when poured 

 upon three or four times its own weight of ice." " I suppose," con- 

 tinues Mr. Guthrie, "the anhydrous chloride may be viewed as separat- 

 ing the atoms of the water-molecule, as is supposed to be the case with 

 the chlorides of phosphorus." 



In using hydrochloric acid as a cryogen with ice. Professor Guthrie 

 obtained a normal acid, and poured it, in various proportions, upon ice 

 at 0°. Fifty grammes of ice were used in each experiment. The table 

 shows within what small limits of ratio the minimum temperature is 

 reached. The weight of ice is taken as unity. 



"We are, therefore," says Mr. Guthrie, "when dealing with a cryogen, 

 one of whose constituents is a liquid, much more limited in the range of 

 ratio which we may employ, to procure the maximum cold, than is the 

 case when both are solid." 



