2 Organic Acids in the Examination of Minerals. 



group,* in the valuation of manganese ores, and in many other 

 processes. 



The behavior of minerals with the organic acids named 

 has been only casually studied, and in but few instances ; T. 

 Sterry Huut,t following Karsten, has made use of acetic acid 

 in the proximate analysis of mixtures of calcite, dolomite, and 

 magnesite, and in the separation of limestone and serpentine ; $ 

 J. Lawrence Smith§ has remarked the solubility of anglesite 

 in ammonium citrate; calamine is sometimes distinguished 

 from willemite by its gelatinizing with acetic acid; || and min- 

 eralogists often resort to the comparatively weak acetic acid 

 for the purpose of " cleaning up" minerals associated with the 

 easily soluble calcite. So far as we can learn, no systematic 

 examination of the action of organic acids on minerals has 

 previously been made; yet the field proves to be wide and 

 fertile. 



During a mineralogical excursion in the summer of 1876, 

 among the rugged mountains of western North Carolina, the 

 impracticability of transporting liquid mineral acids suggested 

 to the writer an examination of the behavior of minerals with 

 solutions of citric and tartaric acid, which are capable of being 

 carried in the solid state. Subsequently a few preliminary 

 trials established the fact that our preconceived notions of 

 the weakness of organic acids as respects minerals were 

 erroneous, and led to the investigation recorded in the follow- 

 ing pages. 



It became necessary at the very outset to collect a consid 

 erable number of minerals in a state of great purity and of 

 normal physical condition : our own small collection supplied 

 these in part, but we would have been embarrassed in this 

 research without the kind assistance of Prof. Thomas Egleston, 

 who generously placed the rich treasures of the School of 

 Mines' mineralogical collection at our disposal, and to whom 

 we tender our sincere thanks. 



* W. Goold Levison, American Journal of Science, |2] r, 240. 

 t American Journal of Science, [2] xxvm, 180, and xlii, 64. 



* Geol. Canada, 1863, 609. 



§ American Journal of Science, [2] xx, 244. 

 || Dana's System Min., 5th edition, p. 408. 



