and Attached Water. 355 



3. When solutions stronger than the cryohydrate, below 0° 

 C, are cooled, either the anhydrous salt or some hydrate richer 

 in salt than the cryohydrate separates. 



It follows that the cryohydrate may, and indeed must inevi- 

 tably be reached both by cooling a solution weaker than the 

 cryohydrate (ice separates, the solution strengthens, the tem- 

 perature sinks), and by cooling a solution stronger than the 

 cryohydrate (anhydrous salt or a hydrate richer than the cryo- 

 hydrate separates, the solution weakens, the temperature sinks). 

 Assuming as a fact that which will be abundantly proved, 

 namely that every salt which is soluble above 0° C. is also 

 soluble below 0° 0. (we shall see that there is even no quanti- 

 tative discontinuity at 0° C. in the solubility), it follows immedi- 

 ately that a solution of any degree of strength whatever gives 

 rise on cooling, sooner or later, to a liquid which remains unso- 

 lidified until the proper ratio and- temperature is reached, and 

 then solidifies in that constant ratio and at that constant tem- 

 perature. From a solution of the strength of the cryohydrate 

 nothing separates until the proper temperature is reached. 

 And then, however rapid the absorption of heat may be, the 

 temperature never sinks lower until solidification is complete. 



§ 124. I propose in the present communication (1) to trace 

 the history of solutions weaker than the cryohydrates as they 

 yield ice on cooling, and (2) to examine the separation of an- 

 hydrous salts or hydrates richer than the cryohydrates when 

 solutions richer than the cryohydrate are cooled. With regard 

 to the first of these branches of inquiry, the only experiments 

 in this direction which I have described are those relating to 

 chloride of sodium in § 10, and those concerning spirits of 

 wine in § 96. 



A solution of a salt below 0° C. which is stronger than the 

 cryohydrate, may be viewed as a solution in the cryohydrate, 

 either of a hydrate richer than the cryohydrate or of the anhy- 

 drous salt. A solution of a salt below 0° C. which is weaker 

 than the cryohydrate may be properly regarded as a solution 

 of ice in the cryohydrate. A solution of chloride of sodium 

 stronger than its cryohydrate may be also regarded as a solu- 

 tion of the subcryohydrate, Ka CI 2 H 2 O (?), in the cryohydrate 

 (§15). 



Just as a given weight of water dissolves at temperatures 

 above 0° C. T with rare exceptions, more of a salt the higher 

 the temperature, so a given weight of the cryohydrate dissolves 

 more ice at higher temperatures, below 0° C, than at lower 

 ones. The weaker a given weight of a salt solution below 0° 

 C. is, the smaller is the weight of the cryohydrate in it, and 

 accordingly the less is the weight of ice which the given weight 



2B2 



