266 The Earl of Berkeley on Solubility and 



(22) The evidence for the existence o£ a limit to the 

 supersaturation of a solution seems to be strengthened by the 

 following. 



Numerous investigators * have shown that supersaturated 

 solutions can be made to crystallize out by mechanical shock. 

 Thus, Mr. Applebey, working in my laboratory in the usual 

 way with sealed glass tubes containing the solution, together 

 with a short length of brass rod. has obtained results with 

 supersaturated sugar solutions which show that the faster 

 the tabes are shaken, the higher the temperature at which 

 crystallization takes place — the maximum speed he was able 

 to use was 700 up and down strokes per minute, and the 

 freedom of path of the 1*5 inch length of No. 5 B.A. brass 

 rod was about one inch. 



(23) I have lately made some experiments similar to those 

 described by Young t. Various forms of apparatus were 

 devised and tried ; the most successful of these is shown in 



%• 6 - 



The glass tube A (one inch internal diameter), containing 

 the solution, is rigidly held in the water bath, which is 

 furnished with a thermostat and stirrer (not shown). The 

 steel anvil B, whose upper surface has been rendered as 

 hard as possible by quenching in a freezing-mixture, passes 

 through the indiarubber stopper closing the lower end of A. 

 A brass tube C, passed through the upper indiarubber 

 stopper, acts as a guide for the steel rod D, whose lower end 

 is ground hemispherical and also hardened ; this rod is 

 normally held about 0'5 mm. from the surface of B by means 

 of the thin rubber tubing E, but it is brought into violent 

 contact with the anvil when the spring F is released. The 

 mechanism actuating the spring explains itself. 



It was found that some forty blows, each developing a 

 pressure of approximately 20,000 atmospheres in the steel at 

 the point of impact, caused a solution of 71 per cent, sugar to 

 crystallize out within 3° C. of the temperature of saturation ; 

 while Mr. Applebey gets the same solution out with the most 

 rapid shaking only within 6 0, 5 of the crystallizing point. 



(24) If we remember that increased rapidity of shaking 

 means an increase in the force of impact, and that the 

 pressure developed in my experiments is much greater than 

 in Mr. Applebey's, we may, following Young, state that the 

 greater the blow the closer we can bring the supersolubility 

 to the solubility curve. Assuming that the solutions are on 



* Miers and Miss Isaac, Harold Hartley with several collaborators, 

 and others. 



t Journal American Chem. Soc. vol. xxxiii. p. 148 (1911). 



