312 Scientific Intelligence. 



used was slightly in excess of the molecular proportion, and the 

 silicate formed was therefore slightly acid. This solution was 

 added to a neutral solution of AgN0 3 , and a lemon-yellow pre- 

 cipitate was thrown down. This was washed carefully with hot 

 water, and dried. Dried between filter paper, the salt retains 

 its original yellow color, but when completely dried in a bath, 

 the color becomes darker. Two analyses gave the following 

 results : 



Agfi 77*42 77*41 



SiO„ 22-66 22-52 



100-08 99-93 



Ag 2 Si0 3 requires Ag 2 7945, Si0 2 20-55. This salt is, then,, 

 slightly acid, which agrees with the conditions of the precipi- 

 tation; as the meta-silicate of sodium was slightly acid. From 

 this it appears that all that is necessary to prepare a silicate of 

 silver of a certain composition, is the pure corresponding 

 sodium salt, and a neutral silver solution. 



The silicate of silver is readily decomposed by all acids, and 

 is perfectly soluble in ammonia. It bears a considerable degree- 

 of heat without decomposition, first changing its color to 

 brown red, then back to the original yellow, a red heat, how- 

 ever, resolves it into Ag, O, and Si0 2 . 



The above is intended merely as a preliminary notice, as I 

 am still engaged in a further study of the salt and will publish 

 my results when they are complete. 



Laboratory of the Globe Smelting and Refining Co., Denver, Colorado. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. On the Determination of Vapor Density below the Boiling 

 Point. — Demuth and V. Meyer have modified the Meyer vapor 

 density method so as to allow the determination to be effected at 

 temperatures below the boiling point of the substance employed. 

 In Hofmann's method this object is attained in consequence* of 

 the diminished pressure, as is well known. The author conceived 

 that the same result might be reached by filling the bulb of the 

 Meyer apparatus with hydrogen, a gas lighter than air and also 

 of greater diffusibility. The apparatus used is essentially the 

 same. The material whose vapor-density is to be determined, if 



