p. C. WILHELMSEN, R. LUMRY AND H. EYRING 93 



their effect on fluorescence yields. Groups like the amino group which 

 greatly increase the intensity of the chemiluminescence generally in- 

 crease the fluorescence yields of substituted aromatic compounds as 

 can be seen in Table 11. This taken with the investigations of Zellner 

 and Dougherty (1937) seems to indicate that the influence of the 

 substituents on the aromatic nucleus is on 4> rather than on the reac- 

 tion itself. 



TABLE II 



" These values are from Spruit (1950). 



Hydrazine is weakly luminous when oxidized by ferricyanide. How- 

 ever, the mechanism seems to be different from that involved in the 

 usual chemiluminescence of the DPD's in that oxygen apparently has 

 no effect on the quantity of light emitted. The relatively high effi- 

 ciency of the Hght produced by the DPD's appears to require the 

 cyclic ring structure with the two hydrogens available to form the 

 dienol form. 



End Products and Intermediates 



The identification of the intermediates and end products of a reac- 

 tion is of great value in elucidating the mechanism. The efforts to 

 isolate these from the chemiluminescent reaction of the DPD's have 

 not been particularly successful. The conditions required for the 

 chemiluminescence favor the subsequent reaction of the end product 

 and the various substituted phthalic acids that have been isolated, 

 eg 3-aminophthalic acid from luminol, might represent ultimate 

 reaction products rather than the direct product of the chemilumines- 



