186 The Philippine Journal of Science ms 



COLORLESS ALKALI SALTS OF PHTHALOXIME 



The effect of temperature upon molecular equilibrium is little 

 understood, but there is undoubtedly a decreased activity at low 

 temperatures. Alcohol solutions of phthaloxime show less 

 yellow color when cooled in a mixture of solid carbon dioxide 

 and ether. This may be due to a decreased activity of hydrogen 

 toward the partial valencies of the unsaturated groups, or may 

 be caused by a change in the equilibrium of molecular rearrange- 

 ment. When a cold alcohol solution of sodium ethoxide was 

 added to the above oxime solution, crystals of sodium salt were 

 precipitated in an almost colorless form. These showed no 

 increase of color as long as they were kept cold in the freezing 

 mixture, but rapidly turned red after filtering from the mother 

 liquor, due in all probability both to the rise in temperature and 

 the condensation of water. The colorless crystals may be taken 

 as the true oxime type of salt, regardless of which theory be 

 applied to explain the colored compounds. 



THE ABSORPTION SPECTRA OF PHTHALHYDROXAMIC ACID 



Alkaline solutions of phthaloxime salts suffer rapid transforma- 

 tion into salts of phthalhydroxamic acid 25 with loss of identity 

 between the white and the yellow isomer. 28 It appears that the 

 difference between the two forms depends upon the integrity 

 of the double bond between carbon and nitrogen, and that this 

 is destroyed when the hydroxamic acid forms. Moreover, the 

 free hydroxamic acid when heated in solution gives phthaloxime, 

 the white isomer forming at 60° and the yellow at 100°. The 

 formation of hydroxamic acid may be due to the increased activ- 

 ity of molecular vibration when hydrogen is replaced by a metal 

 atom or to the tendency of the rearranged molecule to take up the 

 elements of water. However, phthaloxime suspended in distilled 

 water gradually forms hydroxamic acid upon standing even in 

 the presence of mineral acid and without passing through a 

 colored stage, so it is not essential to assume a different molecu- 

 lar condition as necessary for the transformation. Alkali 

 appears merely to accelerate the rate of reaction, without in- 

 fluencing the final product. This is further evidence that the 

 oxime and its salts possess identical molecular structure. 



For purposes of photographing the absorption spectrum of the 

 hydroxamic acid, alcohol solutions of oxime were treated with 

 an excess of alkali and allowed to stand until colorless. 



25 Lassar-Cohn, loe. cit. 



26 Orndorff and Pratt, loc. cit. 



