sn 



acid also admit of snpersaturation. But in all these case;^, the amount 

 of substance held in excess though appreciable, is small. 



Copper chloride "and nickel chloride which are highly soliii)le, 

 can form fairlj' 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, hydratcd 

 or anhydrous, sparingly soluble or highly soluble, can form super- 

 saturated .solutions. 



Now, experiments of a quantitative character were under- 

 I I taken with a series of substances. The experiments were 

 j / conducted in the following way : A bulb was lilown at 

 one end of a tube of about 10 mm. diameter, and a 

 portion towards the other end drawn out a little so as to 

 form a constriction there. The tube was then very care- 

 fully washed and steamed to dissolve away any nuclei, 

 carefully dried, and weighed. A weighed amount of the 

 pure dry substance was introduced into it, a little water 

 was added to it, and a supersaturated solution produced 

 by properly adjusting the amount of the solvent by boiling. 

 The solution was freely boiled so that every particle on 

 the side of the tube passed into solution. The (ulie was 

 then partially cooled under the tap, and carefidly sealed at the con- 

 striction by means of a blow-pipe. The solution was then rolled 

 over the stem of the bulb to mix with the condensed droplets of 

 water there, and thus a homogeneous solution was obtained. The 

 tube was then thoroughly cooled and placed in a quiet place with 

 a thermometer to indicate (he temperature. The drawn out portion 

 of the tube was dried, and this weighed with the sealed bulb, gave 

 the weight of water added. 



To reach the maximum amount of supersatnration, which can 

 be maintained under ordinary circumstances for an hour or .so, the 

 method of trial was adopted. The solution was often boiled a little 

 and cooled down in tap water to see whether crystals ap|)ear 

 immediately. By a little practice no difficulty was felt to judge in 

 this way whether the solution would crystallise shortly or not. The 

 tube was sealed when this stage was reached. 



The time for which the solution remained supersaturated, as well 

 as the temperature at which crystallisation set in were carefully 

 observed. 



The following table .shows the cxperiuienlal data. The solubilit}' 



