﻿Theory of Freezing Mixtures. 791 



In fig. 1 this range is represented by the right-hand sloping- 

 portion of the curve, which is practically a straight line. 



Series of experiments were carried out to test the 

 validity of the above work. Not very much importance 

 was attached to the absolute value of the cryohydric tem- 

 perature reached all along the central portion of the curve, 

 as this depended very largely on the purity of the materials 

 used. One set of results is recorded below : — 



We 



ight of Salt, 

 gm. 



Weight of Ice. 

 gm. 



Percentage of 



Sal tf f s . 



T. 



•80 



27-6 



2-82 



8-0 



•98 



32-2 



295 



12-5 



1-20 



34-4 



3-37 



150 



lu-7 



511 



17-3 



19-8 



5-0 



230 



17-8 



20-0 



12-5 



54-2 



18-7 



198 



13-7 



50-7 



21-3 



19-8 



156 



44-3 



26-0 



20-8 



200 



45-0 



30-8 



20-5 



21-2 



47-0 



312 



20-5 



280 



59-1 



322 



198 



360 



36-3 



49-8 



19-7 



382 



172 



68-9 



19-9 



45-8 



41 



91-8 



12-0 



46-1 



3-1 



93-8 



7-0 



37-7 



2-3 



94-0 



30 



The above results were obtained by mixing the ice and 

 salt in a small vacuum flask, great care being taken to 

 make the mixing as complete as possible : this was fairly easy 

 until the percentage of salt was high, say over 75 per cent. ; 

 but for high percentages it was probably imperfect at best. 

 The results agree with those expected from theory except 

 for high concentrations of salt ; and, even for such, they 

 are sufficiently close to substantiate the previous work. 

 Poor mixing and the thermal capacity of the vessel would 

 cause such a deviation. 



In the practical case of the use of refrigerating- mixtures, 

 the body to be cooled is always to be taken into account, and 

 it may produce considerable modification. If its thermal 

 capacity is 6, the equation would now read 



T 5 + l +0]=ML„. + mL,. 



