1085 
other evidences has shown that calcium fluoride is isomorphous 
with calcium chloride, but it will be seen that calcium fluoride 
cannot release the supersaturation of a solution of caleium chloride. 
Experimental Procedure. 
A bulb was blown at one end of a clean piece of soft glass 
tubing of length of about 12 ems. and of internal diameter of about 
10 mms. A little constriction was made near the open end of the 
tube in order to facilitate its sealing off, The bulb tube was carefully 
cleansed and well steamed and then dried in an air oven. Now the 
tube was weighed (@,) and then a weighed amount of the substance 
(w,) in question was poured upon a small funnel held at the open 
end of the tube. By small additions of water the salt was completely 
dissolved and the funnel was washed. (C.f. Buarracnaryya and Duar. 
Proc. Royal Acad. Amsterdam 1915, 18, 369). 
The tube was now heated to boiling of the solution over a BunsEn 
flame for some minutes and by some trials it could be ascertained 
that a supersaturated solution is obtained. 
In this connection it is worth while mentioning that stable super- 
saturated solutions of almost all substances conld be prepared by 
this simple method (e.g. supersaturated solutions of such sparingly 
soluble substances as potassium perchlorate, potassium chlorate, 
benzoie acid, salicylic acid ete. have been prepared). 
The tube containing the supersaturated solution was cooled and 
carefully sealed off at the constricted portion and kept in an un- 
disturbed position. 
Usually after the lapse of two hours the solution was vigorously 
shaken for some minutes in order to observe the effect of mechanical 
shaking on crystallization, but in almost no cases did crystallization 
begin on shaking. 
The bulb containing the solution as well as the sealed-off portion 
of the tube were weighed (w,) and from these we can calculate 
the amount of supersaturation. 
Now the mouth of the bulb was broken and a small amount of 
the isomorphous substance was added and vigorously agitated for 
about 15 minutes. If no crystallization sets in, a small crystal of 
the dissolved solid was added and shaken; in this case, copious 
crystallization immediately begins. 
In some cases, instead of using a weighed amount of the substance 
each time, a concentrated solution of the substance is prepared and 
standardised. In each observation 5 e.c. of the standardised solution 
are used and thus the amount of the substance taken is known. 
