24 



KAXSAS ACADE3IY OF SCIENCE. 



with it in the same way. I found that the pure salt did not interfere in any way with 

 the digestive action of the fluid, and therefore the inference is that the pure salt is 

 insoluble in the gastric fluid. An analysis was made of the fluid after it had been 

 standing at 100° F. in contact with the pure chromate; no reaction indicating the 

 presence of the salt could be obtained.' 



Prof. E. H. S. Bailey has since examined the commercial chrome yellow, and finds 

 it to contain variable quantities of barium and calcium sulphate. The latter salt is 

 sufiiciently soluble to account for the above modified action of the digestive fluid. 



Dr. Marshall, of Philadelphia, has made some physiological experiments upon 

 dogs which lead him to believe that chrome yellow is decomposed by the muriatic 

 acid of the stomach. The so-called poisonous property cannot be due to the solu- 

 bility of the salt, but it might be accounted for by the gradual decomposition of the 

 salt in the tissues, which retain considerable portions of the insoluble powder. 



OX THE OCCURREXX'E OF NITRITES IN RAIN-WATER. 



BY PROF. G. H. FAILYER. 



As a part of our work upon the nitrogen compounds occurring in rain water we 

 have tested qualitatively for nitrites, using the test proposed by Griess and modified 

 by Warrington.* The test is almost too delicate to be used quantitatively, but in 

 all cases we tried to grade the color produced by a purely artificial scale; such as faint, 

 distinct, strong, very strong. In general, as might be expected, the depth of color 

 produced varies inversely with the amount of rain, since the first portion of the fall 

 would serve to wash the air, and any subsequent fall would only dilute the solution. 

 But the amount of this has been quite variable, for extremely heavy rains have some- 

 times shown good reactions. This may be due to the production of nitrites during 

 the shower, or, in a long-continued rain, the air being renewed at any one place may 

 bring in fresh supplies of the salts. 



To illustrate the results obtained, I give a summary for the year justclosed (Oct. 

 1886 to Sept. 1887, inclusive.) 



October 



November 



December 



January 



February 



March 



April 



May 



June 



July 



August 



September 3 



Total.. 



69 



It seems remarkable that so many of the rain-waters should show the presence 

 of nitrites. It is equally remarkable that the winter months should be deficient in 

 these compounds. Is it because oxidation is then at a minimum, or is it that reduc- 



*See Journal of the Loudon Chem. Soc. for May, 1881. 



