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SCIENCE PROGRESS 



plates. A pure crop does not always result at the first attempt, 

 but the crystals of the deep yelllow form, if any are present, 

 show up very clearly against the almost colourless ones, and can 

 be at once detected with a lens. 



The solubilities of the two forms in alcohol are given in the 

 subjoined table as the number of grams of the compound con- 

 tained in ioo grams of the saturated solution. 



Solubility of the Enantiotropic Forms oj Phthalylphenylhydrazide in 

 Ethyl Alcohol 



The solubility curves given in fig. 1 show that the transition 

 point lies in the neighbourhood of io°. 



« 0-8 



£ 



2 



E 

 t 



o 01 



Temperature. 



Fig. 2.— Phthalylphenylhydrazide in alcoholic solution. 



p.Y. = pale yellow form. d.y. = deep yellow form. 



At this temperature, however, phthalylphenylhydrazide 

 is so sparingly soluble in alcohol that the difference in solubility 

 of the two forms is of the same order of magnitude as the ex- 

 perimental error. The transition point could not, therefore, 

 be determined exactly, using this solvent. 



