} } 



HEAT. 155 



quantity of heat, which produces cold. By applying this 

 principle to the conversion of certain salts into liquids, an 

 intense degree of cold may be produced. Thus by mix- 

 ing two parts of snow with one part of muriate of soda, 

 (common salt), a degree of cold 5 below zero may be 

 produced. Dry potash, (carbonate of potash,) mixed with 

 snow will produce cold 53 below zero. 



The following table shows the proportions of different 

 ingredients, and the degree of cold produced by mixing 

 them together, In all cases the effect is produced by the 

 sudden conversion of the solid salts into liquids. 

 Cold mixtures, produced without snow or ice. 



Mixtures. Parts. Thermometer sinks. 



From 50 to 4 c . 



Sulphate of Soda (Glauber's Salt) 3 ) 50 to 10 



Diluted Nitric Acid (AquaFortis) 2 ) below zero. 



Sulphate of Soda 8 \ 

 Muriatic Acid (Spirit of Salt > " 50 to zero. 



or Marine Acid) 5 ) 



Phosphate of Soda 9 ) o o 



Nitrate of Ammonia 6 > 



Diluted Nitric Acid 4$ below zero. 



Cold mixtures with snow and ice. 



mixtures. Parts. Thermometer sinks. 



Snow or pounded ice 3 \ 



Diluted Sulphuric acid, } From 32 to 23 below 0. 

 (oil of Vitriol,) 2 j 



" l40- bdw 0. 

 Snow 2 \ 



Crystallized muriate of > " 32 to 50 below 0. 



lime 3 ) 



If these materials are cooled down before they are 

 mixed, by exposure to frigorific mixtures, a much greater 

 degree of cold may be produced in some cases thus, in 

 the last mixture, in the above table, if the snow and 

 muriate of lime be cooled down to 40 below zero, and 

 then mixed, a cold of 73 below zero will be produced. 

 The greatest degree of cold ever produced by artificial 

 means, was 93 below zero. 



