boys’ department. 
379 
AGRICULTURAL CHEMISTRY—No. 8. 
I will here repeat the names of those elements 
belonging to the soil, with which I promised to ac¬ 
quaint you in this letter. They are potassium, so¬ 
dium, magnesium, calcium, chlorine, iodine, bro¬ 
mine, manganese, phosphorus, and silicon. You 
recollect I told you that there are but sixteen ele¬ 
ments that enter into the composition of vegetables; 
with the remaining six, viz. oxygen, hydrogen, ni¬ 
trogen, carbon, iron, and sulphur, you are already 
familiar. 
Potassium is a metallic substance, of a white and 
brilliant appearance, but soft as wax, and lighter 
than water. When exposed to the air, it attracts 
oxygen very rapidly, and this union of potassium 
and oxygen forms the well known alkali, potash. 
When a piece of potassium is thrown on water, it 
attracts the oxygen of the water with such rapidity 
as to become ignited, and burns with a white flame 
while swimming on its surface. Potassium and 
oxygen combine in two proportions; the one con¬ 
taining the lesser portion of oxygen is called the 
protoxide , the other the peroxide of potassium. The 
prefix, pro, to any of the oxides, denotes the lowest 
proportion of oxygen, or degree of oxidation, and 
per, the highest which they contain. Potash is an 
important ingredient in the potato vine, grape vine, 
corn stalk, and most other trees and plants. 
Sodium is another metallic substance, uniting 
readily with oxygen, and forming the alkali called 
soda. These two alkalies (potash and soda), are 
found in almost every vegetable, and their presence 
is consequently necessary to the fertility of every 
soil. Sodium also unites with oxygen in two pro¬ 
portions, forming a protoxide and peroxide of so¬ 
dium. The protoxide is the soda of commerce, 
and this, combined with muriatic acid, forms our 
common table salt, the chemical names for which 
are muriate, or hydrochlorate of soda. 
Magnesium is a white metal, and bright like sil¬ 
ver. It also unites readily with oxygen, and the 
protoxide forms the magnesia of commerce. This 
also possesses slight alkaline properties, and unites 
with some of the acids, forming various saline com¬ 
pounds. Epsom salts is a combination of magnesia 
with sulphuric acid, and its chemical name is there¬ 
fore sulphate of magnesia. 
Calcium is a brilliant white metal, which, when 
united with oxygen, produces lime; quicklime is, 
therefore, an oxide of calcium. Lime is a very im¬ 
portant agent in every soil, and I will speak of it 
more particularly hereafter. It possesses a strong 
affinity for carbonic acid, which it absorbs from the 
atmosphere, forming a carbonate of lime. Chalk 
and marble are both composed of lime and carbonic 
acid. In its pure state, lime combines readily with 
nearly every acid, forming a multitude of salts. 
Combined with sulphuric acid, it forms gypsum, or 
plaster of Paris, the chemical name for which is 
sulphate of lime. 
Chlorine is a green-colored and poisonous gas, 
and is never found in nature except in combination. 
United with hydrogen, it forms muriatic acid ; com¬ 
bined with mercury in one proportion, it forms cal¬ 
omel • another proportion of chlorine changes the 
calomel to corrosive sublimate, or bichloride of 
mercury, a most deadly poison. The combinations 
of chlorine with the metals are called chlorides. 
Iodine is of a black color, and when uncombined 
is in the form of small, shining scales, which are 
changed by a high degree of heat into a beautiful 
violet vapor. Its combination with metals are 
called iodides. 
Bromine is a fluid, possessing an offensive odor, 
and having properties similar to iodine. It has 
been considerably used of late years in the process 
of taking Daguerreotype likenesses. Chlorine, 
iodine, and bromine, are only found in such plants 
as grow along the sea shore, or in salt marshes, and 
are consequently of little importance to the agricul¬ 
tural chemist. 
Manganese is a black mineral, always found in 
nature in connexion with iron, and having proper¬ 
ties similar to those of iron. It unites with oxygen 
in two proportions, and its protoxide forms a num¬ 
ber of salts, some of which are occasionally found 
in the ashes of plants, and are supposed to answer 
as a substitute for iron. 
Phosphorus is a light, inflammable solid, colorless 
when perfectly pure, and insoluble in water. It 
is an important constituent in bones, from which it 
is obtained for various uses in the arts. As its 
presence is always necessary for the production of 
seeds, it is an essential ingredient in all our culti¬ 
vated plants. It combines with oxygen, forming 
phosphoric acid, and this, combined with metallic 
bases, forms a large group of salts called phos¬ 
phates. 
Silicon is a substance resembling charcoal, and 
but little known in its pure state. It is the base 
of silicic acid, called also silica and silex; this is 
pure sand, though possessing chemical properties 
which give it a place among the acids. Its com¬ 
pounds with soda, potash, &c., are called silicates. 
The presence of rushes indicates an abundance of 
silica in the soil where they grow. It is a very 
important agent in the production of some or our 
most common plants. 
You may be curious to know how iron, and 
some of the other minerals which I have described, 
can ever enter into, and become a part of any vege¬ 
table. Although this is not the place for showing 
how plants obtain their food from the soil, yet 1 
may as well here inform you that these solid sub¬ 
stances usually combine with certain acids which 
are present, and from salts, which are either dis¬ 
solved by water, or some other agent, and then im¬ 
bibed by the roots of the plant in the same manner 
as water itself. When the ashes of any vegetable 
are analysed, some of these metals are always 
found in the form of salts. 
J. McKinstry. 
Greenport, Columbia Co.,) 
Nov. 1st, 1848. \ 
Facts in Farming. —The more dung, the 
heavier green crops; the more green crops, the more 
cattle food ) the more cattle, the more dung. Hence, 
by keeping an abundance of cattle, a farm can be 
improved from year to year. 
Comparison of Manures.— The manure of a 
horse may nearly equal that of a cow, setting qual¬ 
ity against quality; and that made by two or three 
pigs may be equal in value to that of an ox. 
