CHEMISTRY. 643 



III. — Water of Mammoth Hot Springs. 



Grains in imp. gallon. 



Sodium sulphate 34. 44 



Sodium chloride 18. 90 



Calcium carbouate 17. 92 



Magnesium carbouate 8. 68 



Silica : 3. 36 



83.30 



IV. — Deposit from Mammoth Hot Springs. 



Calcium carbouate 96. 80 



Magnesium carbonate 1. 36 



Alumina and iron 0. 45 



Silica 0. 25 



Water 0. 50 



99.36 

 ( Am. J. Sci.j cxxv, 104 and 351.) 



Decomposition of Minerals by Citric Acid. 



H. Carrington Bolton has continued his investigations as to the action 

 of organic acids on minerals, and publishes the following results. The 

 acid employed was citric acid, which, as the author has shown, has a 

 power of decomposing minerals little less than that of hydrochloric 

 acid ; the effect of prolonged action at ordinary temperatures was espe- 

 cially considered. Of the sulphides, chalcocite showed signs of decom- 

 position at the end of ten days, and after several months a partial solu- 

 tion of a green color was obtained; pyrite was attacked in eight days, 

 and a month later a solution of a reddish yellow color was obtained ; 

 chalcopyrite acted similarly ; one gram lost 11 per cent, after fourteen 

 months' contact with the citric acid solutiou. Of the oxides magnetite 

 and limonite were strongly attacked iu eight days, hematite yielding 

 more slowly. Of the silicates datolite was the most quickly decomposed, 

 yielding gelatinous silica after twenty-four hours; hornblende, pyrox- 

 ene, almandite, epidote, and serpentine were decidedly decomposed in 

 eight days, and after fourteen months the last named yielded a dry, ge- 

 latinous mass. The feldspars are unequally attacked under like condi- 

 tions ; labradorite yielded most easily. Muscovite and biotite yielded 

 very slowly, the latter showing signs of decomposition the sooner, mi- 

 nute scales and slimy silica separating after two years' subjection to the 

 acid solution. 



