■±18 Scientific Intelligence. 



solution is heated, the change of the character of the color 

 being due, as mentioned above, to the fact that the undisso- 

 ciated molecule as well as its dissociated ions are colored. 

 In reference to these observations he says : — '* A glance at the 

 above observations will suffice to show that where the color is 

 not materially altered in character, it invariably becomes more 

 intense when heated, that is to say fewer rays are transmitted ; 

 * * * The elevation of temperature seems to heighten the 

 absorbent power of the dissolved salt, so that the light absorbed 

 by a certain quantity of the heated solution is the same as 

 would have been absorbed by a larger quantity of the same 

 solution, if cold." 



We now know that this absorbing power is exercised by the 

 ions as well as by the salt in solution, and that just as the color 

 is the more intense the more concentrated the solution, so is it 

 also, the more numerous the dissociated ions. And, to repeat, 

 as heat increases the number of dissociated ions of a salt in 

 solution, so does it deepen the shade of color of the solution. 



Note. — Just before receiving the proof of the above paper, there came to my 

 notice the articles " On the Dissociation of Electrolytes in Solution as shown by 

 Colorimetric Determinations" (Chem. News, vol. Ixvi, pp. 104, 114, 141, 152) 

 by H. M. Vernon. B. A., the experimental data of which afford additional proof of 

 the correctness of the views expressed above. 



Chicago, 111. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. On the Relative Densities of Hydrogen and Oxygen. — 

 Rayleigh has continued his researches on the relative densities 

 of hydrogen and oxygeu. In his first paper (1888) he gave 

 15*884 as the ratio obtained. Subsequently he effected a direct 

 synthesis of water and obtained the ratio 15 - 89. He says: "I 

 had intended further to elaborate and extend my observations 

 on the synthesis of water from weighed quantities of oxygen and 

 hydrogen, but the publication of E. W. Morley's masterly re- 

 searches upon the ' Volumetric Composition of Water' (Amer. 

 Jour. Set., March, 1891) led me to the conclusion that the best 

 contribution that I could now make to the subject would be by 

 the further determination of the relative densities of the two 

 gases. The combination of this with the number 2*0002 obtained 

 by Morley as the mean of astonishingly concordant individual 

 experiments, would give a better result for the atomic weights 

 than any I could hope to obtain directly." In the present ex- 

 periments, the gases were obtained electrolytically, the generator 

 being a long U-tube containing a solution of potassium hydrox- 



