and Attached Water. 



25 



separates from an aqueous solution of ethylamine of any and 

 every strength between — 13°*9 and the anhydride is one of 

 those remarkable bodies which I have called subcryohydrates, 

 and which have been observed in the chloride and iodide of 

 sodium. 



The subcryohydrate of ethylamine, as a glance at the 

 curve (fig. 1) will show, has a solidifying-point within cer- 

 tainly one tenth of a degree C. of —8°, and, as certainly, it 

 has within two or three tenths of a per cent, the composition 

 of 32 '4 per cent. It is minutely crystalline, and of nearly the 

 same specific gravity as the residual liquid. Its solution is 

 eminently supersaturable, and in that state is curiously viscid. 

 It is not easy to see a way whereby it might be made to 

 purify itself in the act of formation. The existence of these 

 solid hydrates of a substance which by itself resists solidifi- 

 cation by a carbonic-acid cryogen, and the fact that their 

 melting-points are only ten degrees or so below 0°C, is 

 surely an unanswerable argument that they are not mere 

 juxtapositions of independent crystals of the two constituents. 



Any horizontal line between — 13°'9 and —8° cuts the 

 curve of aqueous ethylamine in three places. Within these 

 limits, therefore, there are always three degrees of strength of 

 the solution, which begin to solidify at the same temperature. 

 Thus, if we find an aqueous solution of ethylamine begin to 

 solidify at —12°, we do not know whether it is of the strength 

 18-7 or 22*2 or 43*3 per cent. Further, it may be noted that, 

 on adding water of the air-temperature to the solid subcryo- 

 hydrate, a depression of temperature occurs to a point lower 

 than that at which the subcryohydrate stood. 



Table XLVI. 

 Separation of Solids from Aqueous Solution of Ethylamine. 







Tempera! ure 





Per cent, of 



Per cent, of 



at which 



Nature of 



Ethylamine. 



water. 



solidification 

 begins. 



solid. 



* 0-9901 



99-01 



o 



- 04 



Ice. 



5 



95 



- 2-0 



„ 



10 



90 



- 4-7 



f 



15 



85 



- 8-4 



n 



20 



80 



-13-3 



f} 



20-64 



79-36 



-13-9 



Cryohydrate. 



25 



75 



- 9-5 



Subcryohydrate. 



30 



70 



- 8-1 



,, 



324 



67-6 



- 8-0 



„ 



35 



65 



- 8-2 



f 



40 



60 



-101 



>j 



50 



50 



-164 





* Accidentally taken 1 to 100, instead of 1 to 99. 



