THE ARTESIAN WATER SUPPLY OF EASTERN FLORIDA.

case probably results from reducing properties of decaying organic matter, the sulphates being first reduced to sulphides according to the following reaction: Na2 $ 04+C2 (carbon of organic matter) -2CO2+Na2S. The sulphide is then acted upon by the carbonic acid to form H2S as follows: Na2S+H2'CO3-H2S+ Na2CO3. The reaction of organic matter upon the sulphides is regarded by Van Hise as another important source of H2S in underground water.*
The formation of hydrogen sulphide as a result of the action of acids upon metallic sulphides is one of the most familiar of laboratory experiments. This suggests the possibility of the formation of this gas as the result of the action of acids upon metallic sulphides contained in the rocks. Sulphides, especially those of iron, are widely scattered in the earth's crust and occur in sufficient quantity to account for the formation of H2S gas in water. Hydrogen sulphide is a weak acid and its salts are decomposed by a stronger acid. Sulphuric and other mineral acids should certainly react upon sulphides liberating H2S. Carbonic acid, when abundant, reacts upon alkali sulphides to produce hydrogen sulphide. I: is true that the alkali sulphides are normally not abundant in the crust of the earth. Stokes has shown, however, that the reaction of sodium carbonate within the earth upon pyrite or marcasite produces sodium sulphide. The reaction given by him is as follows: (1. c. page 1107).
8FeS2+I 5Na2CO3-4Fe2O3+ I4Na2S-+Na2S203+ I5CO,2,
It is a well-known fact that the carbon dioxide which unites with water to form carbonic acid is abundant in the deep waters, especially in the limestone formations, the pressure existing at considerable depth enabling the water to hold great quantities of carbonic acid. The series of reactions given by Stokes accounts for the presence of alkali sulphides in solution in the deep waters. It may be added that all sulphides are soluble to some extent in water and in that condition may be acted upon by carbonic acid.t
The partial oxidation of sulphides is, acording to Van Hise. a possible additional method of formation of hydrogen sulphide, the reaction being as follows: (1. c. p. I I 13).
3FeS2+4H20+40-Fe3O4+4H2S+2SO2.
*A Treatise on Metamorphism, Mon. XLVII U. S. Geol. Surv., page 11i2, 1904.
"t'norganic Chemistry. International Library of Technology. Sec. 12, p. I K.

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