124 Messrs. Illingworth and Howard on the Thermal 



considerable ; while the kind of difference is not to be com- 

 pared with that resulting from the substitution of an acid or 

 basic element in a given salt. 



We have accordingly submitted to examination the sul- 

 phomethylate, the sulphoethylate, and the sulphoamylate of 

 potassium (K, CH 3 S0 4 ; K, C 2 H 6 S0 4 ; and K, C 5 H n S0 4 ) ; 

 and we venture to think that the results are of sufficient 

 interest for us to give the following brief account of them. 



We satisfied ourselves that the substances were nearly pure. 

 The methyl salt contained, however, a trace of chlorine, and 

 the amyl salt was not quite free from the same impurity. 

 They were finely powdered, and dried over sulphuric acid in 

 partial vacuum until they ceased to lose weight. A thermo- 

 meter, the error of which at 0° was determined, and which 

 was graduated to tenths of a degree (each tenth being -f G 

 millim. long), enabled us to read temperatures with consider- 

 able precision. 



Sulphoethylate of Potassium (K, 2 H 5 S0 4 ). — Starting with 

 the ethyl salt, a preliminary examination, made by mixing the 

 salt with about twice its weight of finely crushed ice, showed 

 the cryogen value to be — 1 3°*9 C. This, according to analogy, 

 should be the melting- and solidifying-temperature of the 

 cryohydrate. Solutions containing various percentages of 

 the anhydrous salt were made and submitted to a salt- ice 

 cryogen, the temperature being noted at which solidification 

 began. 



With regard to the solubility at the air-temperature : — A 

 solution saturated at 21° C. was allowed to cool for several 

 hours until it reached 15°'l C. Of this solution, 7*3342 

 grams were weighed in a covered basin and then dried in 

 vacuo over sulphuric acid. The nearly dry mass was powdered 

 and redried until it ceased to lose weight. 4*5732 grams, 

 or 62*35 per cent., were thus obtained. 



A solution saturated at the air-temperature was fairly buried 

 in melting ice for several hours and until its temperature had 

 remained for a few hours at 0° C. Examined as above, 

 24*0880 grams gave 12*9375 grams of anhydrous salt, or 

 53*71 per cent. 



A solution of strength between 40 and 50 per cent, was 

 cooled in an ice-salt cryogen until its temperature remained 

 constant at — 14°*2 C. After a considerable amount had 

 solidified, 11*9813 grams of the solution were dried, and 

 yielded 5*3932 grams dry salt, or 45*01 per cent. It will be 

 noted that the temperature of the cryogen of this salt was 

 found to be — 13°*9, or 0°*3 higher than the melting-point of 

 the cryohydrate. 



