DR. CHARLES A. BURQHARDT ON COPPER-ORES. 253 



periments in this direction and obtained interesting results, 

 which, however, we have not yet sufficiently worked out to 

 publish them. 



Another question to be elucidated is, what is the che- 

 mical constitution of aurin ? According to E. and O. 

 Fischer, that of pararosaniline is 0,^11,, (NH^), from which 

 it follows that aurin is C,4.H,,(0H)j. Already, in our first 

 research, we obtained results which seem to confirm this 

 view. On heating aurin with acetyl chloride, we obtained 

 a colourless crystalline compound which, on analysis, gave 

 results nearly agreeing with the composition of triacetyl 

 aurin, C,gHn(OCiHjO)j ; and on using benzoyl chloride a 

 similar benzoyl compound was obtained. The analytical 

 numbers, however, did not sufficiently agree with those 

 required by theory ; and therefore we did not publish them ; 

 and as the purification of these compounds was found to 

 be beset with several difficulties, we did not then examine 

 them further, because we believed the study of red aurin 

 would more readily throw light on the subject. We have 

 now prepared them again from pure aurin, and hope to be 

 soon able to settle these points. 



XXXII. The Origin of some Ores of Copper. — Part II. 

 By Charles A. Burghardt, Ph.D., The Owens College. 



Read April and, 1878. 



Atacamite. 

 This interesting and beautiful mineral occurs generally in 



