NovV, experirneiits of a quantitative charadei* were unuef- 
taken with a series of substances. The experiments wei'e 
eondncted in the following way : A huil) was blown 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 eonstrietion 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 
Ü 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 partiele on 
the side of the tube passed into solution. The tube was 
then partially cooled under the tap, and carefully sealcd at the con- 
striction by rneans 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 the 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 supersaturation, 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 w het her crystals appear 
iminediately. By a little pracüce no difficulty was feit 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 experimental data. The solubility 
of the substance was obtained trom Seidell’s Solubilities of Inor- 
ganic and Organic substances. The solubilities were caleulated as 
grams of anhydrous substances per 1 gram of water. The substances 
appear in the list in the order of their water of crystallisation, and 
of their solubility. The substances crystallised in all cases in 1 to 
5 hours after the sealing of the tubes. 
Besides these, some 30 tubes were sealed with Solutions of less 
supersaturation. They were watched for 3 months, in which time 
very few crystallised. 
From the above tables it will be seen that no perfectly general 
