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



On plotting these points on the concentration-temperature diagram fig. 8, it will 

 be found that they also lie very approximately on a continuous curve to the left-hand 

 side of the -, ft-, and y-supersolubility curves, nearly parallel to them, and separated 

 from the y-supersolubility curve by between 4 and 5 of temperature. These points 

 appear on fig. 8, which also gives all the solubility and supersolubility curves for 

 the three modifications. 



It is just possible that these outlying points may give the supersolubility curve 

 corresponding to a fourth, very unstable, modification of monochloracetic acid, and 

 may correspond to that which PICKERING has called 8. 



No other evidence of its existence has, however, been found, and no sign of a 

 fourth modification has ever been seen under the microscope throughout this work ; 

 if it exists at all, it is probably so unstable that it transforms instantaneously into 

 either y or ft. 



These experiments complete the whole of the results obtained from shaking 

 solutions in sealed tubes. 



VI. The Solubility Curves for the Different Modifications of Monochloracetic Acid. 



It has been previously mentioned that PICKERING has determined solubility curves 

 for the three modifications of monochloracetic acid which he calls a, ft, and 8, and 

 also one point on the solubility curve for the modification which he calls y. In our 

 three figs. 5, 6, 7, which give the three supersolubility curves for the modifications a, 

 ft, and y of the acid, the three corresponding solubility curves also appear. On 

 figs. 5 and 6 the solubility curves for the a- and ^-modifications are plotted from 

 PICKERING'S results, but on fig. 7 the solubility curve for the y-modification is plotted 

 from the results obtained below. All three solubility curves have, however, been 

 obtained independently of PICKERING by a method which has been used before in our 

 previous work. 



Weighed quantities of the monochloracetic acid and water were enclosed in sealed 

 glass tubes. They were then heated in a water bath until all the acid crystals had 

 dissolved, except one or two very small crystals which were preserved at the upper 

 end of the tube. The tubes were then allowed to cool gradually in a beaker of water 



