8. Oxide of Manganese is a brown powder, which consists of oxygen in combination with a metal resembling iron, to which the name of manganese is given. It exists in plants, and in soils only in very small quantity.
9. Sulphur.—This substance is well known. It generally exists in the ash in the state of sulphuric acid (oil of vitriol), which is a compound of sulphur with oxygen. It does not always exist in living plants, however, in this state.
Sulphuric acid forms with potash a sulphate of potash,—with soda, sulphate of soda (or Glauber’s salts),—with lime, sulphate of lime (gypsum),—with magnesia, sulphate of magnesia (Epsom salts),—with alumina, sulphate of alumina,—and with oxide of iron, sulphate of iron or green vitriol. When the sulphate of potash is combined with sulphate of alumina, it forms common alum.
10. Phosphorus is a soft pale yellow substance which readily takes fire in the air, and gives off, while burning, a dense white smoke. The white fumes which form this smoke are a compound of phosphorus with oxygen obtained from the air, and are called phosphoric acid. In the ash of plants the phosphorus is found in the state of phosphoric acid, though it probably does not all exist in the living plant in that state.
Phosphoric acid forms phosphates with potash, soda, lime, and magnesia. When bones are burned, a large quantity of a white earth remains (bone-earth), which is a phosphate of lime, consisting of lime and phosphoric acid. Phosphate of lime is generally present in the ash of plants; phosphate of magnesia is contained most abundantly in the ash of wheat and other varieties of grain.
11. Chlorine.—This is a very suffocating gas, which gives its peculiar smell to chloride of lime, and is used for bleaching and disinfecting. It is readily obtained by pouring muriatic acid (spirit of salt) on the black oxide of manganese of the shops. In combination with the metallic bases of potash, soda, lime, and magnesia, it forms the chlorides of potassium, sodium (common salt), calcium and magnesium,[7] and in one or other of these states it generally enters into the roots of plants, and exists in their ash.
Such are the inorganic substances usually found mixed or combined together in the ash of plants. It has already been observed, that the quantity of ash left by a given weight of vegetable matter varies with a great many conditions. This fact deserves a more attentive consideration.
SECTION II.—OF THE DIFFERENCE IN
THE QUANTITY OF ASH.
1. The quantity of ash yielded by different plants is unlike. Thus 1000 lbs. of
| Wheat | leave | 12 | lbs. |
| Oats | 26 | lbs. | |
| Turnips | 8 | lbs. | |
| Red Clover | 16 | lbs. | |
| Rye Grass | 17 | lbs. | |
| Barley | 25 | lbs. | |
| Potatoes | 8 | lbs. | |
| Carrots | 7 | lbs. | |
| White Clover | 17 | lbs. |