476 M. Carey Lea — Allotropic Forms of Silver. 



Results of comparison with Solar Spectrum. — It "will be 

 seen by inspection of the tabulated results that nine out of 

 the eleven lines of copper are reversed in the sun, and four of 

 the five of zinc. The conclusion reached in each of these 

 cases was after repeated examination when the conditions 

 were such as to show a clear space between the components of 

 the E line. The latest available authority* gives copper 

 among the doubtful elements in a list of those found in the 

 sun, and on the same list zinc does not appear at all. The 

 present investigation makes it quite probable that zinc, and 

 almost completely demonstrates that copper exists in the solar 

 atmosphere. 



Bowdoin College, March 14, 1889. 



Art. L. — On Allotropic Forms of Silver ; by M. Carey 

 Lea, Philadelphia. 



Silver is capable of existing in allotropic forms possessing 

 qualities differing greatly from those of normal silver. There 

 are three such forms, or rather three modifications of one form, 

 differing from each other in many respects, but all more nearly 

 related to each other than any one of them to normal silver. 

 One of these forms is soluble in water, passing readily to an 

 insoluble form, and this last may, by the the simple presence 

 of a neutral substance exercising no chemical action upon it,, 

 recover its solubility. Another form closely resembles gold in 

 color and lustre. 



Whether metallic silver shall be reduced from its compounds 

 in its normal or in an allotropic form, depends upon the reduc- 

 ing agent applied, so that it cannot be said with any certainty 

 whether it exists in its compounds in its ordinary normal form,, 

 or in an allotropic condition : the latter alternative seems at 

 least equally probable. 



These allotropic forms of silver are broadly distinguished 

 from normal silver by color, by properties, and by chemical re- 

 actions. They not improbably represent a more active condi- 

 tion of silver, of which common or normal silver may be a 

 polymerized form. Something analogous has already been 

 observed with other metals, lead and copper. 



Much having been written, especially within the last few 

 years, on the products of the reduction of silver compounds,. 

 a brief summary of what has appeared may be desirable 

 before proceeding further. The study of this subject has led 

 to remarkable divergencies of opinion on the part of the 



* Young's General Astronomy. 



