408 Koenig — New 



Species 



Melanochalc% 



The percentages 



are : 





Molecules. 



CiiO = 



r6-88 : 



: 79 



= 0-96583 



SiO, = 



1 80 : 



; 60 



= 0-12914 



CO, = 



I'll : 



; 44 



= 0-16295 



H,0 = 



7-71 : 



: 18 



= 0-42833 



ZnO = 



0-41 



: 81 



= 0-00506 



FA = 



0-OV 







0-29208 



100-04 



This unusual, and surely novel composition, may give cause 

 for several interpretations. Roughly speaking, it might be an 

 intimate mixture of copper carbonate, copper silicate and 

 copper hydrate ; but it may also be interpreted as the basic 

 salt of an ortho-silico-carbonic acid H4(Si,C)04, in which Si 

 and C may replace each other vrithin certain limits. A scrutiny 

 of the three analyses shows a practically identical percentage 

 of copper oxide. The percentages of SiO, and of the volatiles 

 vary. As to SiO,, we have 9-91 ("A"); 8-83 O'B"); 7-80 

 (" C "), a variation of about 1 per cent. In " A " we have 

 12-52 volatiles ; in " B," 14-2 ; in " C," 14-88. These figures 

 are evidently not due to accident, nor due to mechanical mix- 

 ture. Unfortunately their significance was recognized only 

 after it was too late for a determination of CO, in " A " and 

 " B," for there was nothing, or too little, of the materials left. 

 JSTotwithstanding this serious experimental deficiency, it seems 

 to me that the logical comparison forces the admission of 

 strength in my hypothesis. Admitted the existence of a com- 

 plex H^Si, 0)0^ . H^O (and I can see no chemical reasons 

 against it) in which hydrogen is wholly replaced by Cn, and 

 HjO partly by CuO and in which, moreover. Si and C are 

 atomically interchangeable : but so that the percentage of Cu 

 be constant, then a change in the percentage of Si^O, must 

 influence both the percentages of CO, and 11,0. Kow, com- 

 paring "A" and " C," we find in the former 2-11 SiO, niore^ 

 and 2*35 volatiles less than in the latter. 2-11 SiO, are equiv- 

 alent to 1*53 CO,, leaving 0-82 as that portion of the volatiles 

 attributable to water, thus conforming with the hypothesis. 



If the composition of melanochalcite be interpreted accord- 

 ing to this plausible hy^Dothesis, the figures of analysis " C " 

 take the following shape. 



Molecules Si,0, = 0-12914 

 *' CO^ — 0-16295 



0-29209 



These 0-29209 molecules require 2x0-29209=0-58418 mole- 

 cules of CuO. 



