38 



E. DIVERS AND T. HAÔA. 



salt, but nevertheless its hot strong- solution in simple writer can be 

 rapifHy cooled and then kept for an hour or more without crystallisino;, 

 and nothino; can l»e objected to allowing that it may show still greater 

 supersatnration in presence of the other salts of its mother-liquoi". 

 Mixtures made to prepare it. yield it at once if cold when a crystal of 

 it is dropped iti or when alcobol is added, free alkali remaining in 

 solution in the latter case, oidy when in excess ofthat required to form 

 the normal salt, and this salt occurring in the alcoholic pi'ecipitate 

 when the alkali is in excess ofthat îiecessarv to tVie composition <jf the 

 pentapotassium salt. But apart entirely from this matter of su])er- 

 saturation. there is in proof that cold dilute alkali converts the neutral 

 salt at once into the alkaline salt, Fremy's experiment, repeated 

 l)y us, of acting u])on the solid neutral salt with potassium hydroxide 

 in aqueous solution (p. 80). The neutral sodium salt also passes 

 readily and at once into the ncjrmal salt on adding sodium hydroxide 

 to it. 



Rasch ig gave as a chemical property distinguishing between the 

 neutral and alkaline salts, the activity of alkali sulphite upon the 

 former and inactivity upon the latter. We have not succeeded our- 

 selves in finding anything in Claus's writings upon this subject, but 

 Raschig adduced Glaus in evidence of his statement. Fremy's wi-it- 

 ino-s, however, are sufficient to show that the above distinction, so far 

 as it holds good, serves only to mark the alkalinity of the alkaline 

 salt, for he points out that sulphurous acid first converts the basic 

 sulphazotate to the neutral sulphazotate and then acts upon this salt. 

 To this we may add that metasulphite and alkaline oximidosul]ihonjite 

 change together into normal sulphite and neutral oximidosulphonate, 

 and that when enough metasulphite is added all oximidosulphonate is 

 quickly destroyed. 



There yet remains for consideration one other ground taken by 



