220 Hillebrand and Penfield — The Alunite-J arosite Group. 



species. Other members of this group will doubtless be 

 found, and the name natroalunite might be employed to 

 designate the two varieties of alunite from Colorado men- 

 tioned on page 216, where the proportion of the soda to the 

 potash molecule is 7 : 4. It is highly probable that a series of 

 alunite-j arosite compounds could be made artificially. 



It is with pleasure that the writers acknowledge their indebt- 

 edness to Messrs. Turner and Porter for calling attention to 

 the interesting compounds described in this article. 



Laboratories of the U, S. Geological Survey, Washington, and of the 

 Sheffield Scientific School. Yale University, New Haven, 

 Feb., 1902. 



