Organic Acids in the Examination of Minerals. 11 



8. Acetic acid does not act so energetically on the mineral 

 carbonates as do the preceding; moreover, on boiling, the 

 volatile acid distills off and the solution becomes weaker as 

 the heating is continued ; whereas with solutions of the solid 

 acids, boiling increases their concentration and their decom- 

 posing power. We conjecture that experimenters in this 

 direction have been deterred from further research by the 

 unsatisfactory nature of the reactions with acetic acid. And 

 yet, if we may trust the ancient chronicles of Rome, the beha- 

 vior of minerals with this acid was investigated at a very 

 early period ; we refer to that much disputed tradition which 

 represents the celebrated Carthaginian general, Hannibal, 

 applying vinegar to the removal of rocks that obstructed his 

 passage across the Alps, in his march on the Roman capital : 



" Diducit scopulos et montem rumpit aceto." * 



Glacial acetic acid does not in the slightest degree dissolve 

 calcite; even pure precipitated calcium carbonate does not 

 effervesce when boiled with glacial acetic acid ; but on adding 

 one-fourth part of water, effervescence begins at once and the 

 carbonate dissolves freely. 



The behavior of carbonates with acetic acid may be sum- 

 marized as follows (Sp. gr. of acid = 1.037). 



(a) Calcite, gurhofite, witherite, cerussite, baryto-calcite, and strontia- 

 nite effervesce freely in the cold and dissolve rapidly on heating. 



(&) Dolomite, ankerite, sinithsonite, and azurite effervesce slightly in 

 the cold, the action being increased on boiling. 



(o) Magnesite, siderite, rhodochrosite, and malachite are not attacked 

 in the cold, and dissolve more or less readily on boiling. 



9. Formic acid (Sp. gr. =1.060) acts rather more powerfully 

 than acetic ; cerussite gives a peculiarly beautiful and charac- 

 teristic deposit of lustrous white crystals. Malic acid also 

 acts quite energetically ; but the difficulty of obtaining it in a 

 state of purity, and its high price, will prevent its use in this 

 connection. It does not seem especially desirable to extend 

 the list of organic acids ; for though their number is legion, 



* Juvenal, Satire X. 



