THE ARTESIAN WATER SUPPLY OF EASTERN FLORIDA. 
105 
case probably results from reducing properties of decaying organic 
matter, the sulphates being first reduced to sulphides according to 
the 'following reaction: Na2 S O4+C2 (carbon of organic mat¬ 
ter) = 2 C 02 +Na 2 S. The sulphide is then acted upon by the 
carbonic acid to form H2S as follows: Na2S+H2'C03=H2S+ 
Na 2 C 03 - 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 form¬ 
ation 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. Hydro¬ 
gen 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 abun¬ 
dant, 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 reac¬ 
tion of sodium carbonate within the earth upon pyrite or marcasite 
produces sodium sulphide. The reaction given by him is as fol¬ 
lows: (1. c. page 1107). 
8FeS2+i5Na2C03=4Fe203+i4Na2S+Na2S203+i5C02, 
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 acidT 
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. 1113). 
3 FeS2+4H20+40=Fe304+4H2S+2S02, 
*A Treatise on lytetamorphism, Mon. XLVII U. S. Geol. Surv., page 
1112, 1904. 
flnorganic Chemistry. International Library of Technology- Sec. 12, p. 11. 
