340 



PRINCIPAL HENEY A. MIERS AND MISS FLORENCE ISAAC ON THE 



PART I. MONOCHLORACETIC ACID AND ITS AQUEOUS SOLUTIONS. 

 A. The Different Modifications of Monochloracetic Acid. 



The first accurate measurements of the crystals obtained from solution in water 

 were given by SCHMELCHER (' Zeits. f. Krystallographie,' 1892, vol. 20, p. 115), who 

 described them as belonging to the monoclinic system with the elements 



a : 6 : c = 0-8176 : 1 : 0-5G33 ; /3 = 70 43', 

 and as presenting the forms 



B = {010}, p = {2W}, o = {lll}, = {Oil}. 



The angles are : 



pp = 42 12', 



qq =56 5', 

 oo = 42 0', 

 oij = 26 30', 

 op = 39 40'. , 



The plane of cleavage, B, is perpendicular to the third mean line ; and there is also 

 a good cleavage parallel to (100). (See fig. 1.) 



B 



FIG. I. 



FIG. 2. 



As was pointed out by PICKERING (' Journ. Chem. Soc.,' 1895, vol. 67, p. 664), there 

 are in reality certainly three, if not four, modifications to be distinguished. 



The crystals described by SCHMELCHER were obtained from solution in water. 



The following are the appearances presented by the substance as it cools from fusion 

 or crystallises from aqueous solution. 



