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



been shown in the above experiments. The positions ojf these curves, therefore, account 

 for the relative stability and instability of the ft- and y-crystals respectively. As has 

 been shown, a shower of y-crystals in a closed tube always transforms to ft or a on 

 shaking the solution, but a /3-shower very rarely transforms to a. 



VIII. Additional Experiments with Pure Monochloracetic Acid, 



All the monochloracetic acid used in these experiments is the ordinary commercial 

 acid, and, as has been mentioned, it in all probability contains a little water even 

 when it is dried in a desiccator, as it is very hygroscopic. In order to determine the 

 true melting-points of the different modifications of the pure dry acid, a few additional 

 experiments were made with a small quantity of the acid which had been specially 

 purified for this purpose by Mr. NAGEL, to whom we are much indebted for kind 

 assistance. 



Experiment 105. The acid was enclosed in five sealed tubes. Two of the tubes 

 contained corundum fragments with the acid ; two, glass fragments, and the remaining 

 tube contained the pure acid alone. The melting-points of all three modifications, 

 a, ft, y, were found in the manner already described, and gave the results : 



Modification. Melting-point. 



............. 62'4, 



ft ............. 56'5, 



y ............. 51. 



The melting-points found above, using the commercial acid, were : 



Modification. Melting-point. 



ft ............. 55, 



7 ............. 50, 



while the corresponding points found by PICKERING were : 



Modification. Melting-point. 



ft ............. 56-01, 



y ............. 50. 



It is, therefore, certain that both the acid used in this research and that used by 

 PICKERING contain a little water, and this conclusion is also borne out by the 

 experiments 2, 18, 34. 35, &c., on the refractive indices, where the acid was used 



