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KINETICS OF CHEMILUMINESCENCE 



cent reaction. The compound 2,2'-dicarboxylbenzil has been obtained 

 by Zellner and Dougherty (1937) and confirmed by Drew and Gar- 

 wood (1938) from the oxidation of unsubstituted DPD. The fact that 

 this compound can be further oxidized to phthahc acid without the 

 production of Hght makes it probable that it is more closely related 

 to the actual product of the light producing reaction than the phthalic 

 acid derivatives. The alternative is that it is produced by a side reac- 

 tion in which case there would be no relationship between it and the 

 product of the chemiluminescence. The preparation of possible inter- 

 mediates has been reported (Kautsky and Kaiser, 1950; Drew and 

 Garwood, 1938). The compound prepared by Kautsky and Kaiser has 

 not been proven to be related to the chemiluminescence of the DPD's. 

 Drew and Garwood (1938) prepared a compound by dissolving lu- 

 minol in strong alkali and adding a large quantity of hydrogen 

 peroxide which they assumed to be an intermediate in the chemilu- 

 minescent reaction. The subsequent adding of alcohol and cooling 

 caused the precipitation of a crystalline compound. The analysis of 

 this compound showed it to be the mono sodium salt. Drew supposed 

 the compound was the hydrated form of 



NH2 



o- 



I 



o 





 OH 



NH 



NH 



and did find that one molecule of water could be removed by drying 

 in a vacuum over phosphoric oxide. The subsequent analysis was in 

 substantial agreement with the proposed compound. However, it was 

 found that some hydrogen peroxide was lost by heating and essentially 

 all of it was lost when the compound was heated to 120° C. This 

 seems to indicate that the compound isolated was one where hydrogen 

 peroxide had replaced one molecule of water of crystallization. Drew 

 has reported that the compound dissociated in water and that essen- 



