28 



Frederick Guthrie on Salt-Solutions 



The subcryohydrate of this body is, like those of the pre- 

 viously examined ones, very prone to supersaturation ; so 

 that, in examining the richer solutions, it is advisable to have 

 recourse to the solids of previous preparations; which act like 

 a ferment. A nearly remelted tubeful of the subcryohydrate, 

 set to resolidify very slowly, crystallizes in bright laminae one 

 or two millimetres in diameter. More quickly frozen in repose, 

 crystalline masses an inch long are fashioned upon the glass. 



Table XLVIII. 

 Separation of Solids from Aqueous Solutions of Triethylamine. 



Per cent, of 



Per cent, of 



Temperature 



of initial 

 solidification. 



Nature of 



Triethylamine. 



water. 



body formed. 



5 



95 



- 10 



Ice. 



10 



90 



- 20 



>> 



15 



85 



- 2-9 





18 



82 



- 34 



>9 



19-1 



80-9 



- 3-8 



(Jryohydrate. 

 S ubcry ohy drate. 



20 



80 



- 35 



30 



70 



- 41 



>) 



40 



60 



- 54 



'» 



50 



50 



- 6-7 



5) 



70 



30 



-13-6 



5} 



80 



20 



-20-6 





For the curve, see fig. 1, p. 31. 



§ 238. Triethylamine is one of those rare bodies which, like 

 sulphate of sodium, sulphate of calcium, caustic lime, and 

 a few others, are more soluble in cold than in hot water. The 

 behaviour of the three bodies named is clearly traceable to 

 the decomposition by heat of definite hydrates. Without 

 laying undue stress upon this, it seems that the phenomenon 

 in question is one of decomposition, which so often follows 

 increased temperature, and not an inversion of the rule that 

 solubility also increases with temperature. The body decom- 

 posed in the case before us is clearly a hydrate — either the 

 cryo- or subcryohydrate. Accordingly, though striking in 

 its presentation, the phenomenon is really quite continuous 

 with the decomposition by heat of oil of vitriol ; which decom- 

 position, I presume, does actually take place when that liquid 

 is heated above its boiling-point (in a closed vessel). But 

 while in the latter case the products of decomposition are 

 probably miscible, and mix, though held apart from chemical 

 union by heat-tension, with the hydrates of ethylamine the 

 products of thermal decomposition are separated not only 

 chemically but in mass, because, when chemically separated, 

 they are not molecularly miscible, at least in all proportions. 



