THE ASH OF PLANTS. _ 129 
salts of manganese. Its hydrate, prepared by decompos- - 
ing protosulphate of manganese by lime-water, is a white 
substance, which, on exposure to the air, shortly becomes 
brown and finally black from absorption of oxygen. The 
salts of protoxide of manganese are mostly pale rose-red 
in color. 
Sesquioxide of Manganese, Mn, 0,, occurs native as the 
mineral braunite, or, combined with water, as manganite. It is u sub- 
stance having a red or black-brown color. It dissolves in cold acids, 
forming salts of an intensely red color. These are, however, easily de- 
eomposed by heat, or by organic bodies, into oxygen and protosalts. 
Red Oxide of Manganese, Mn; 0,, or Mn O, Mn, O3.—This 
oxide remains when manganese or any of its other oxides are subjected 
to a high temperature with access of air. The metal and the protoxide 
gain oxygen by this treatment, the higher oxides lose oxygen until this 
compound oxide is formed, which, as its symbol shows, corresponds to 
the magnetic oxide of iron. It is found in the ashes of plants. 
Black Oxide of Manganese, Mn 0..—This body is found 
extensively in nature. It is employed in the preparation of oxygen and 
chlorine, (bleaching powder), and is an article of commerce. 
Some other metals occur as oxides or salts in ashes, though not in 
such quantity or in such plants as to possess any agricultural significance 
in this respect. 
Alumina, the sesquioxide of the metal ALUMixvUM, is found in con- 
-Siderable quantity (20 to 50 per cent) in the ashes of the ground pine 
(Lycopodium). It is united with an organic acid (tartaric, according to 
Berzelius; malic, according to Ritthausen) in the plant itself. It is often 
found in small quantity in the ashes of agricultural plants, but whether 
an ingredient of the plant or due to particles of adhering clay is not in 
all cases clear. 
Zinc bas been found in a variety of yellow violet that grows in the 
zinc mines of Aix la Chapelle. 
Copper is frequently present in minute quantity in the ash of trees, 
especially of such as grow in the vicinity of manufacturing establish- 
ments, where dilute solutions containing copper are thrown to waste. 
The salts or compounds of metals with non-metals 
found in the ashes of plants or in the unburned plant re- 
main to be considered. 
Of the elements, acids, and oxides, that have been no- 
ticed as constituting the ash of plants, it must be remark- 
ed that with the exception of silica, magnesia, oxide of 
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