SPONTANEOUS CRYSTALLISATION OF MONOCHLOEACETIC ACID, ETC. 363 



verify the super solubility curve by an independent method. It is evident that glass 

 fragments do not cause sufficient friction in a tube to bring down the /J-shower 

 exactly at the labile point. For instance, a tube containing a few glass fragments and 

 95'062 per cent, of the acid could not be made to give a /8-shower till the temperature 

 had fallen to 35. It is seen from the above table that a tube of the same 

 concentration containing corundum or tinstone crystallises at 37. Numerous other 

 similar results were obtained in which tubes containing only glass fragments passed 

 somewhat into the labile state before giving the showers, but they are omitted in 

 the above table. 



3. Tubes giving y-showers. 

 (All these tubes contain glass fragments.) 



If these 10 points be plotted on the concentration-temperature diagram of fig. 7, 

 containing the results of the experiments on refractive indices in which y-showers 

 were obtained, they will be found to lie very approximately on the y-supersolubility 

 curve there shown. These tube experiments may therefore be regarded as confirming 

 the y-supersolubility curve obtained by the method of refractive indices. 



4. Outlying Points. During the course of the experiments with solutions enclosed 

 in sealed glass tubes with a few glass fragments it was occasionally found that the 

 solution failed to crystallise anywhere in the neighbourhood of either of the super- 

 solubility curves a, /J, or y, but passed quite into the labile region before crystallising. 

 No reason could be assigned for their behaviour, since they were treated in precisely 

 the same manner as usual, being heated to between 60 and 80 for various lengths of 

 time to dissolve the crystals, and then shaken continually as they cooled in a water 

 bath. All the temperatures of crystallisation were, however, recorded, and the 

 following are the collected results giving these outlying points in the labile region. 

 When examined under the microscope, the crystals proved to be always ft or y. 



3 A 2 



