406 
tube have been dissolved away by the steain, the eork is iramediately 
put in, and the hot solution, then, is glided over the side of the 
tube 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 solution might evaporate 
and deposit minute crystals on the sides, which would then atonce 
release the supersaturation. 
But such things can hardly take place in this case, because the 
solution is in a partial vacuum saturated with water vapour. With 
ordinary arnount of precaution man}" supersaturated Solutions were 
prepared in this way which would not deposit crystals even when 
shaken vigorously. 
Thus it lias been found that tartaric acid, citric acid, magnesium 
sulphate, lead acetate, cobalt chloride, microcosmic salt, sodium 
formate, ammonium acetate, copper sulphate, borax form highly 
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 
arnount of supersaturation is not as extensive as in the case of the 
previously 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 
acid also admit of supersaturation. But in all these cases, the arnount 
of substance held in excess though appreciable, is small. 
Copper chloride and nickel chloride which are highly soluble, 
can form fairly supersaturated Solutions, but the range of dilution 
in which they can exist as such in good stability, is rather 
limited. 
Thus it is shown qualitatively that the phenomenon of super- 
saturation is perfectly general, and all sorts of substances, hydrated 
or anhydrous, sparingly soluble or highly soluble, can form super- 
saturated Solutions. 
