136 HOW CROPS GROW. 
Chloride of Sodium, Na Cl, 58.5—This substance is 
common or culinary salt. It was formerly termed muriate 
of soda. It is scarcely necessary to speak of its occur- 
rence in immense quantities in the water of the ocean, in 
saline springs, and in the solid form as rock-salt, in the 
earth. Its properties are so familiar as to require no de 
scription. It is rarely absent from the ash of plants. 
Besides the salts and compounds just described, there 
occur in the living plant other substances, most of which 
have been indeed already alluded to, but may be noticed 
again connectedly in this place. 
These compounds, being destructible by heat, do not 
appear in the analysis of the ash of a plant. 
Nirrates: Witric acid—the compound by which nitro- 
gen is chiefly furnished to plants for the elaboration of the 
albuminoid principles—is not unfrequently present as a 
nitrate in the tissues of the plant. It usually occurs there 
as Nitrate of Potash, (niter, saltpeter.) 
The properties of this salt scarcely need description. It 
is a white, crystalline body, readily soluble in water, and 
has a cooling, saline taste. When heated with carbonaceous 
matters, it yields oxygen to them, and a deflagration, wr 
rapid and explosive combustion, results. Zouch-paper is 
paper soaked in solution of niter, and dried. The leaves 
of the sugar-beet, sun-flower, tobacco, and some other 
plants, have been found to contain this salt. When such 
vegetables are burned, the nitric acid is decomposed, often 
with slight deflagration, or glowing like touch-paper, and 
the alkali remains in the ash as carbonate. The characters 
of nitric acid and the nitrates will be noticed at length in 
another volume, “‘ How Crops Feed.” 
OxaLaATEs, Cirrates, Manares, TArTRATES, and salts of 
other less common organic acids, are generally to be found 
in the tissues of living plants. On burning, the bases with 
which they were in combination—potash and lime in most 
cases—remain as carbonates. 
