CLDMALOOTTi 



THE 



AMERICAN JOURNAL OF SCIENCE 



[THIRD SERIES.] 



Akt. XXYIII. — On AUotropic Silver ; by M. Caret Lea. 



Part II. — Relations of AUotropic Silver with Silver as it exists 

 in Silver Compounds. s 



The first part of this paper* was devoted to the examination 

 of one of the well marked forms of allotropic silver, — the gold- 

 colored. The blue form in its soluble and insoluble varieties 

 will be more particularly described in a future paper. The 

 subject at present to be considered is the relation existing 

 between the allotropic forms of silver taken generally and 

 silver as it exists in its compounds and more especially in the 

 silver haloids. 



It is a well established law that when a substance is capable 

 of existing in two forms, of which one is a polymer of the 

 other, the polymeric form possesses greater density and less 

 chemical activity. Combination is usually accompanied with 

 loss of activity, and the polymerization of a body consists in its 

 combination with itself. When a substance is capable of exist- 

 ing in two allotropic forms and of being converted from the 

 one to the other by pressure, the body resulting from pressure 

 is always the more dense of the two and is a polymer of the 

 first. f In the case of allotropic silver these laws appear to be 

 verified. I have shown elsewhere that gold-colored silver has 

 a specific gravity of 8*5, while that of normal silver is 10*5 to 

 106. The greater chemical activity of the gold-colored form 

 is demonstrated b} T its greater affinity for oxygen, sulphur and 



*In the March number, pp. 179-190. 



f See examination by Spring of the effect of pressure, Ber. D. Ch. Ges., xvi, p. 

 1002, 1003. 



Am. Jour. Sci.— Third Series, Vol. XLI, No. 244.— April, 1891. 

 17 



