374 PRINCIPAL HENRY A. MIERS AND MISS FLORENCE ISAAC ON THE 



enclosed in sealed glass tubes. Fragments of glass or of corundum were also enclosed 

 in the tubes with the various mixtures, and the tubes were heated to about 70 or 80 

 uatil the crystals had completely dissolved. They were then shaken violently by 

 hand as they cooled in a water-bath, and the temperature at which the dense shower 

 of spontaneous crystallisation occurred was noted. Each mixture will crystallise 

 either as naphthalene or the a-, ft-, or y-modification of the acid, and will therefore 

 give a point on one or other of the four branches of the supersolubility curves. As 

 soon as crystallisation took place in a tube, it was immediately examined under the 

 microscope, and the crystals which had formed were identified. After an intimate 

 acquaintance with the various crystals, it was, however, found quite easy to identify 

 them with the naked eye as soon as they formed in the tube, and in some cases this 

 was necessary, as the change of temperature caused by taking the tube out of the 

 water-bath and examining it under the microscope sometimes caused the second 

 component of the mixture to crystallise as well as the original shower to increase, or 

 the change of temperature sometimes caused a transformation from one modification 

 of the acid to another. 



The nature of the material introduced into the tube to produce friction appears to 

 have considerable effect on the temperature of spontaneous crystallisation, and also 

 operates in bringing down certain modifications. For instance, corundum enclosed in 

 a tube containing a certain mixture will bring down an a- or /J-shower much more 

 frequently than a y- or naphthalene shower. Tubes containing glass fragments give 

 y- and naphthalene showers more readily than a- or /3-showers, and when an a- or 

 /3-shower does occur in a tube containing glass fragments it usually does so at a lower 

 temperature than in a tube of equal concentration containing corundum. The glass, 

 however, appears to be quite as effectual as corundum in bringing down showers of 

 naphthalene or of the y-modification of the acid. As in the aqueous solutions of the 

 acid, /3-showers occur much more frequently than a-showers. 



The following is a record of all the results obtained for the spontaneous crystal- 

 lisation of liquid mixtures of naphthalene and monochloracetic acid by shaking the 

 sealed tubes violently by hand in a cooling water-bath, and the observations are 

 plotted in fig. 9. 



