A SOLUTION OF OXALIC ACID AND URANIUM SALTS AS A 

 CHEMICAL PHOTOMETER. 1 



By Raymond F. Bacon. 

 (From the Chemical Laboratory, Bureau of Science, Manila, P. I.) 



The study of tropical sunlight was begun by H. D. Gibbs two and 

 one-half years ago in this laboratory. 2 Although the classical researches 

 of Bunsen and Roscoe and others have already thrown much light on the 

 effects of sunlight in various parts of the world on certain chemical 

 reactions and certain differences in the character of sunlight in the 

 Tropics and in temperate zones have been discussed b} f these authors, 

 still many interesting facts have presented themselves during the nine 

 years of existence of this tropical laboratory, which convince all of us 

 that the subject is still very obscure. Therefore it has been decided to 

 take up the investigation from several standpoints, in order to determine 

 in what ways the sunlight reaching the earth in the equatorial zone 

 differs from that in other latitudes; preliminary work having indicated 

 that, for many chemical reactions the effect of the sunlight is much 

 more pronounced in the Tropics than would seem to be indicated by the 

 former investigations of others. Biologic literature is filled with articles 

 detailing various effects, mostly deleterious, of tropical sunlight on animal 

 and vegetable life, and there seems to be a general belief that the Tropics 

 are not suitable as a permanent residence for white men. One of the 

 principal reasons generally assigned for this condition is the effect of the 

 sunlight. It is obvious that any experiments made with living forans 

 can not be as exact as when nonliving matter is used, as in the former 



1 The results so far obtained on this subject are given in the following paper, 

 although the investigation is not as yet complete. The work is being continued 

 by Mr. H. D. Gibbs of the Bureau of Science, and Doctor Bacon will make a 

 series of comparative measurements in Washington, and the joint results obtained 

 by these two investigators, and by others in different parts of the world, will be 

 presented later. (P. C. F.) 



2 A resume of some of the aspects of this work is given in the address of the 

 president of the Far Eastern Association of Tropical Medicine : Freer, This 

 Journal, Sec. B (1910), 5, 1. 



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