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

 4. Solubility of the y -modification of MonocUoracetic Acid in Naphthalene* 



These results, when plotted on the temperature-concentration diagram in fig. 9, give 

 four continuous curves, the right-hand branch being the naphthalene-solubility curve 

 and the three left-hand branches being the solubility curves for the three modifications 

 a, /3, and y of the acid. 



It will be seen also that there are three different eutectics for naphthalene and the 

 three modifications of the acid ; the eutectic for the a-modification and naphthalene is 

 at 53, the composition of the mixture being 30'5 percent, naphthalene, 69'5 per cent. 

 monochloracetic acid ; the eutectic for the ^-modification and naphthalene is at 50'4 

 when the composition of the mixture is 26'25 per cent, naphthalene, 7375 per cent, 

 acid ; and the eutectic for the y-modificatioii and naphthalene is at 44 0- 8 when the 

 composition is 18'1 per cent, naphthalene, 81 - 9 per cent. acid. The freezing-point 

 curve obtained by CADY agrees very approximately with the naphthalene and 

 a-branches here determined, CADY obtaining a eutectic at 53'5 for a mixture of 

 composition 2 1 J'4 per cent, naphthalene, 70'6 per cent. acid. 



In all four branches it has been found possible to continue the solubility curves a 

 little below the various eutectics, and even below some of the supersolubility curves, 

 by cooling the mixture somewhat rapidly in an open tube to below a certain 

 temperature and then inoculating with a minute fragment of the required crystal, 

 which is then carefully watched as the temperature continues to fall slowly. The 

 rapid cooling appears to prevent the spontaneous crystallisation of the other 

 component of the mixture which would normally occur at a somewhat higher 

 temperature had the cooling been gradual. 



This method was also employed in obtaining similar points on the solubility curves 

 below the eutectic for mixtures of salol and betol. 



II. The Supersolubility Curves for Mixtures of Naphthalene and Monochloracetic Acid. 



It has been mentioned in the introduction to this paper that preliminary experiments 

 on the spontaneous crystallisation of mixtures of naphthalene and monochloracetic 

 acid yielded a definite supersolubility curve on the side of the curve representing 

 excess of naphthalene above the eutectic composition, but on the other side of the 



