FREEZING 



487 



II. Table consisting of Frigoriflo Mixtures, composed of ice, with chemical salt* 

 and acids. 



Frigorific Mixtures with Ice. 



N. B. The reason for the omissions in the last column of the preceding table is, 

 the thermometer sinking in these mixtures to the degree mentioned in the preceding 

 column, and never lower, whatever may be the temperature of the materials at mixing. 

 To produce these results in a satisfactory manner, it is necessary to cool, previous^ to 

 the experiments, the vessels in which the mixtures are made. 



A very intense cold may be obtained from the evaporation of a mixture of solid 

 carbonic acid and sulphuric ether, by which a temperature of 166 Fahr. below 

 the freezing point of water is produced. By means of this intense cold, assisted by 

 mechanical pressure several of the gaseous bodies have been condensed into liquids, 

 and in some instances solidified. 



Natterer has obtained a temperature as low as 220 Fahr. by evaporation in vacua 

 of a mixture of liquid nitrous oxide and bisulphide of carbon. 



The following process for producing cold has been patented in this country : 



In a reservoir, or what may with, propriety be called a boiler, was placed a quantity 

 of sulphuric ether. This reservoir was placed in a long vessel of saline water, this 

 fluid by the arrangement being made to flow from one end of the trough to the other, 

 that is to and from the reservoir. In this water was placed a number of vessels, the 

 depth and breadth of the trough, but of only two inches in width, and these were filled 

 with the water to be frozen. 



A steam-engine was employed to pump the air from the reservoir ; this being done, 

 of course the ether boiled, and the vapour of the ether was removed by the engine as 

 fast as it was formed. The heat required to vaporise the ether was derived from the 

 saline water in the trough, and this again took the heat from the water in the cells ; 

 thus eventually every cell of water was converted into ice. The ether was, after it 

 had passed through the engine, condensed by a refrigeratory of the ordinary kind. 

 The statement made by the patentee was very satisfactory, as it regarded the cost of 

 production. An apparatus of this kind is of course intended for hot countries only, 

 where ice becomes actually one of the necessaries of life. 



A peculiar physical fact connected with tho freezing of water has been made avail- 



