CHEMICAL RELATION OF IRON AND MANGANESE. 363 



tion as the hydrous sesquioxide, the carbonate, the sulphide or 

 the hydrous silicate of iron and potash known as glauconite. 

 Manganese under similar conditions is deposited as the hydrous 

 oxide' or as the carbonate, and possibly sometimes, though 

 very rarely, as sulphide. 



When solutions of organic or inorganic salts^of iron and man- 

 ganese are freely exposed to the action of air, as in shallow or 

 rapidly moving streams, or in lakes and some bogs, they are 

 quickly oxidized and both may be deposited as more or less 

 hydrous oxides. In many bogs, however, the metals may be 

 precipitated as hydrous oxide on the surface where oxidizing 

 agencies predominate, but when these oxides sink and come into 

 contact with decaying organic matter, free from the active oxi- 

 dizing influences of the air, they may be reduced to carbonates. 



The carbonates of iron and manganese may be precipitated 

 when the solutions containing them are protected from oxidation 

 by a reducing agent, such as decaying organic matter, or 

 by being far removed from the air. Carbonate of manganese, 

 however, is a much more stable compound than carbonate 

 of iron, and the oxidizing conditions are often sufficiently 

 strong to cause the deposition oi iron as hydrous sesqui- 

 oxide and not strong enough to change the manganese from 

 its carbonate form. It is not uncommon, therefore, to have iron 

 deposited in one place as hydrous sesquioxide, and manganese 

 carried further on and deposited as carbonate, or even under 

 special conditions deposited as carbonate with the hydrous ses- 

 quioxide of iron. Fresenius^ has shown that the warm springs 

 of Wiesbaden, which contain iron and manganese among their 

 other mineral constituents, deposit iron in the form of hydrous 

 sesquioxide, while manganese is carried on further in solution and 

 deposited as carbonate. In this behavior, therefore, we have 

 the first striking difference in the deposition of iron and man- 

 ganese, and it will be further discussed later on. 



' This oxide is generally in the form of the peroxide or the sesquioxide in a more 

 or less hydrous condition. 



*Jahrb. des Vereins f. Naturkunde in Herz. Nassau, Vol. VI., p. 160 (Bischof). 



