^10 



the idea is predominant that only hjdrated salts can be easily snpei-- 

 saturated. Sodium chlorate is cited as a solitary example of an 

 anhydrous salt capable of forming supersaturated solution. Again, 

 no .systematic work of a quantitative character is available in this 

 direction. These led (o the present investigation of showing the 

 general tendency of almost all substances of forming supersaturated 

 solutions. 



At first qualitative experiments were done with varied substances. 

 These were all performed in well cleaned, steamed test tubes fitted 

 with similarly operated corks. The solution is boiled for a few 

 minutes till all the particles of the substance on the side of the test 

 tui)e have been dissolved away by the steam, the cork is immediately 

 put in, and the hot solution, tlien, is glided over the side of the 

 tnbe twice or thrice. The tube is then held under the tap and 

 cooled down to the room temperature. The corks were always 

 moist when they were inserted thus insuring against germ crystals 

 being carried in that way. In open tubes the sohition might evaporate 

 and deposit minute crystals on the sides, which would tiien at once 

 release the supersaturatiou. 



But such things can hardly take place in this case, because the 

 solution is in a partial vacuum saturated with water vapour. With 

 ordinary amount of precaution many supersaturated solutions were 

 prepared in this way which would not deposit crystals even when 

 shaken vigorously. 



Thus it has been found that tartaric acid, citric acid, magnesium 

 sulphate, lead acetate, cobalt chloride, microcosmic salt, sodium 

 formate, ammonium acetate, copper sulphate, borax form higldy 

 supersaturated solutions. In the case of tartaric and citric acids the 

 supersaturated solution is very much viscous, and even on the 

 addition of a small germ crystal of the acid, some time elapses 

 before crystallisation takes place, because the velocity of crystalli- 

 .sation depends on the fluidity of the solution. 



In the case of lead nitrate, barium nitrate, ammonium chloride, 

 strontium chloride, barium chloride, manganese chloride, potassium 

 ferrocyanide, potassium sulphate, zinc sulphate, nickel sulphate, cobalt 

 sulphate, barium chlorate, sodium chlorate, sodium bromate, sodium 

 nitrate, ammonium nitrate, ammonium oxalate, oxalic acid, the 

 amount of supersaturatiou is not as extensive as in the case of the 

 |)revionsly mentioned group. 



The sparingly soluble organic acids, namely, salicylic, benzoic, 

 hippuric, succinic, cinnamic, gallic, phthalic acids can be supersatu- 

 rated. Substances like potassium chlorate, cadmium iodide, boric 



