354 Frederick Guthrie on Salt Solutions 



1. The ebonite electromachines, when constructed with 

 ebonite of good quality, are at least equal to the best machines 

 with glass disks in regard to their action ; but they surpass 

 them by their relatively small expense, nonfrangibility, and 

 permanent electric condition. 



2. The double electromachine constructed by me is a very 

 powerful arrangement for producing electricity in great quan- 

 tity, as well as of great tension. 



3. The substitution of ebonite for glass disks not only de- 

 serves attention because the usefulness is enhanced, but also 

 because new data are acquired, which may be of great interest 

 for the complete theory of electromachines. 



The Hague, March 1876. 



XLIII. On Salt Solutions and Attached Water. 



By Frederick Guthrie. 



[Continued from p. 60.] 



IV. 



Separation of Ice, or of a Hydrate, or of the Anhydrous Salt, 



from solutions of Salts below 0° C. 

 § 123. "TTERY many determinations have been made of the 

 ▼ solubility of various salts in water at tempera- 

 tures ranging from 0° C. to the temperature of ebullition of 

 the saturated salt solution. To Gay-Lussac, to Kremers, to 

 Regnault, and others are due several series of exact determi- 

 nations in this direction of research. But the examination of 

 the phenomena of solidification which take place in salts of 

 certain strengths at temperatures below 0° C. has suffered 

 comparative, almost complete, neglect. And this appears to 

 have arisen partly from the circumstance that it has been 

 asserted by some philosophers, and denied by others entitled 

 to equal respect, that when a solution of a salt below 0° C. 

 begins to solidify by loss of heat, the solid formed is pure ice. 

 It has been my privilege to reconcile the opposing views by 

 the discovery of the fact which I trust now to have fully estab- 

 lished, that when a salt solution which is already any fraction 

 of a degree below 0° C, is cooled, one of three things must 

 happen ; and which of them happens is determined with the 

 same salt by the strength of the solution. 



1. In all solutions weaker than the cryohydrate,ice is formed, 

 at temperatures which are lower according as the solution is 

 richer in salt. 



2, In solutions of a certain strength (namely that of the cryo- 

 hydrate), combination of the salt and water take place in defi- 

 nite ratio and at a constant temperature. The solution is there- 

 fore a melted cryohydrate, and solidifies as a whole. 



