258 Mr. J. Y, Buchanan [May 8, 



influence. This influence, however, is subject to quantitative law 

 which has been well investigated. 



On the same grounds it seems to be legitimate to say that the salt 

 in solution acts also by influence ; and its influence is subject to 

 quantitative law which has been well investigated. 



As both influences are subject to known laws, we are able to ascer- 

 tain the equivalence which exists between them. 



Further, the pressure, being immaterial, is of one kind, while the 

 salt, which is material, is of as many kinds as there are chemically 

 individual substances soluble in water. 



In considering the two agencies, we must compare a certain 

 absolute pressure with a certain weight of a particular salt. In this 

 discourse we have generally considered the constant quantity 1*5105 

 gram chloride of sodium. The generally accepted pressure which 

 lowers the freezing-point of water by 1° 0. is 135 atmospheres, which 

 is here taken as equivalent to 140 kilograms per square centimetre 

 (kg/cm.2). If we consider the surface of the water, which is exposed to 

 the pressure as 100 square centimetres, then the total pressure required 

 is 14,000 kg. We therefore take as our constant absolute pressure 

 14,000 kg. When the distilled water exposes to it a surface of 

 100 cm.2 its freezing temperature is lowered by 1° 0. If the lowering 

 of the freezing-point of water by pressure were simply proportional 

 to the pressure, then, when the surface exposed to the pressure of 

 14,000 kg. is s cm.", the lowering of the freezing-point would be given 

 by t in Table Y. It results, however, from the experiments of 

 Tammann * that proportionality of the lowering of the freezing-point 

 of water to the pressure to which it is exposed, is of the same order 

 as that of the lowering of the freezing-point of water to the amount 

 of salt dissolved in it. In Table Y., s' gives the surface (cm.-) of 

 water which must be exposed to a pressure of 14,000 kg. in order 

 that, according to Tammann, its freezing-point may be lowered by 

 t degrees. The corresponding volumes of ice melted, at ordinary 

 pressure, under the influence of 1*5105 gram NaCl, are given by v. 

 To be sti'ictly comparable with s and s\ the numbers v should be 

 increased in the ratio 98*352 : 100 ; but this has been considered 

 unnecessary. 



It will be seen that the surface of the water exposed to the con- 

 stant pressure, 14,000 kilograms, is roughly proportional to the 

 volume of the ice exposed to the influence of 1*5105 gram NaOl, 

 and to the same volume of water holding in solution 1*6475 gram 

 NaCl, which contains 1 gram chlorine. The proportionality is the 

 closer the greater the surface of the water compressed and the greater 

 the volume of ice which contains the salt. 



In comparing the power of inducing the freezing of water at 



* Ueber die Grenzen des festen Zustandes, von G. Tammann, Annalen 



der Physik. [4], ii. 1. 



