410 Mr. C. Tomlinson on Super saturated Saline Solutions. [May 28, 



is a separation of salt ; and the action of separation once begun, may be 

 rapidly propagated throughout the whole solution. BoiKng saturated solu- 

 tions may be cooled down in chemically clean vessels and kept for any length 

 of time, not because they undergo any molecular change or hold a salt of 

 greater solubility than the normal salt in solution, but they retain their 

 fluid form simply from the absence of a nucleus. 



The salts examined in this memoir are arranged into five groups accord- 

 ing to their behaviour. 



I. Salts of which the supersaturated solutions remain liquid at low 

 temperatures. 



Examples : — Sodic sulphate. 



Sodic acetate. 

 Sodic arseniate. 

 Sodic succinate. 

 Sodic borate. 

 Sodio-potassic tartrate. 

 Potash alum. 

 Magnesia sulphate. 

 Baric acetate. 

 Calcic chloride. 

 Cupric sulphate. 



II. Salts of which the supersaturated solutions suddenly solidify at low 

 temperatures. 



Examples : — Sodic carbonate. 



Sodic phosphate. 

 Plumbic acetate. 

 Sodic hyposulphite. 

 Strontic chloride. 



III. Salts of which the supersaturated solutions deposit their excess of 

 salt at low temperatures or under the action of a nucleus, leaving the mother- 

 liquor saturated. 



Examples : — Zinco-acetate. 



Cupric sulphate. 

 Baric chloride. 

 Potassic arseniate. 

 Antimonio-potassic tartrate. 

 Citric acid. 



IV. Salts of which the supersaturated solutions form modified salts of a 

 lower degree of hydration. 



Examples : — Zinco-sulphate. 



Sodic sulphate. 

 Magnesia sulphate. 

 Ammonia phosphate. 



