496 Frederick Gruthrie on some Thermal and 



pretty fully made out. The conclusion come to in this par- 

 ticular case was that, when the two liquids are brought 

 together, a subcryohydrate is formed, and the heat attending 

 (set free during) its formation may or may not be sufficient 

 to effect its almost complete decomposition, or, rather, mitigate 

 its formation according as the initial temperature of the two 

 liquids is higher or lower. And that subsequent elevation of 

 temperature affects decomposition. Depression of temperature 

 promotes the formation of the subcryohydrate. 



A liquid is in a different predicament from a solid when 

 the question turns upon the solubility in a liquid medium. 

 With a solid, increase of temperature always tends in the 

 direction of fusion per se, which implies diminished cohesion 

 and the bringing of the two (solid and liquid) into a com- 

 munity of physical state. In the case of two liquids, although, 

 as before, rise of temperature may promote solution by di- 

 minishing cohesion, such promotion may be more than coun- 

 terbalanced by the tendency of the increased heat to separate 

 one or other liquid as a vapour, the particles of which, 

 coalescing, form a liquid insoluble in the rest. 



Be this as it may, it will be found that the separation of 

 liquids from their mixtures by increase of temperature is by 

 no means uncommon, and may be the rule rather than the 

 exception long before temperatures approaching the critical 

 ones are reached. 



§ 257. Change of Volume of Triethylamine and Water at 

 about the Temperature of their Separation. — The remarkable 

 separation which takes place between triethylamine and water 

 when a mixture of the two is warmed, and which was de- 

 scribed in § 238, suggests the possible use of such a mixture 

 as a calorimeter. For, if such separation is accompanied by 

 any great change in volume, since the amount of additional 

 heat required to effect a large separation is exceedingly small, 

 a very exact measure of the heat given to the mixture by a 

 given mass of matter cooling through a given range of tem- 

 perature would be obtained by measuring such change of 

 volume. 



I accordingly took a bulb with a capillary stem and deter- 

 mined its capacity up to a lower mark on the stem, and then 

 calibrated the stem. The capacity at 16°*1 was 9*1823 cubic 

 centim. The mean volume of 1 millim. of the stem was 

 •000830038 cubic centim., or 0*00009039 of the capacity of the 

 bulb. Into this bulb 5*4873 grams of water were introduced 

 and then 3*0600 grams of triethylamine, making a 35*8-per- 

 cent. solution. The two on being mixed and brought to the 

 temperature of 16°'l had a volume which may be called V, 



