190 
AGRICULTURAL CHEMISTRY.-NO. 13. 
It is obvious that the mud or other matter sus¬ 
pended in the water, before it is purified, will not 
choke up the strainers, as it commonly does by the 
downward process of filtration, but settle to the 
bottom of the cylinder by means of its own gra¬ 
vity, whence it can be drawn off at pleasure at the 
discharge cock /. As often as the strainers and 
charcoal become infected by animal matter or other 
filth, they can readily be taken out through the 
top of the cylinder, cleansed or renewed, and re¬ 
stored again in their place. The water may be 
kept cool, in summer, by filling the upper chamber 
d, with ice. 
The quantity of water that can be filtered daily, 
by an apparatus of this kind, may vary from five 
gallons to several hogsheads, according to its 
size and the height of the receiving tub above 
the point c. The cost of the whole may vary 
from $10 to $100, according to the size, finish, 
and nature of the materials with which it is con¬ 
structed, as wood, metal, pottery, or stone. 
AGRICULTURAL CHEMISTRY.—No. 13. 
Sugar. —You are familiar with the appearance 
and common properties of sugar, and are aware 
that it dissolves readily in water. The juices of 
trees, grasses, and of cultivated roots contain sugar 
dissolved in them ; and it is also present in the 
juices of fruits, associated with various acids. 
The ultimates , (elementary constituents,) of sugar, 
are carbon, hydrogen, and oxygen. I have pre¬ 
viously informed you how these several elements 
are drawn from the air, and the soil. 
Starch .— This is one of the most abundant pro¬ 
ducts of vegetation. It is found in all those grains, 
or seeds, which are commonly used for food, as 
wheat, rye, oats, &c., and forms a large portion of 
the weight of potatoes, and several other nutritive 
roots. From 40 to 70 per cent, of wheat flour con¬ 
sists of starch. It is also found in the woody fibre 
of some trees. Its presence can always be detect¬ 
ed by mixing a solution of iodine with the sub¬ 
stance supposed to contain it, when, if starch be 
present, it will be changed to a permanent blue 
color. Animal fat is composed of the same ele¬ 
ments as sugar and starch, and for this reason, 
those articles of food containing a large proportion 
of one or both of these substances are most valua¬ 
ble for fattening stock. 
Gum. —There are many different species of gum, 
though they all possess nearly the same chemical 
ingredients. You have doubtless often observed it 
exuding from the trunks or branches of trees ; it 
also exists in the sap of many trees from which it does 
not exude, and is found in greater or less quantity 
in the juices of most plants. 
Woody Fibre. —This is obtained in a state of pu¬ 
rity by boiling small pieces of wood in successive 
portions of water and alcohol. It is thus obtained 
in the form of a white, fibrous mass, without taste 
or smell, and is insoluble in water. Its chemical 
character is always very nearly the same, from 
whatever source it is obtained. Woody fibre forms 
nearly half the weight of the dried stalks of grasses. 
In beets, and many other roots cultivated for food, 
the quantity is small, but increases when the root 
is left in the ground until it becomes old. 
The four proximate principles of plants above 
described, (sugar, gum, starch, and woody fibre,) 
being composed of the same elements, are frequent¬ 
ly changed in plants, or transformed one into an¬ 
other. Thus, “ what is starch in one part of a tree 
may be transformed and conveyed to another part 
of the same tree in the form of sugar. That 
which, in the form of sugar or gum, passes up¬ 
wards or downwards with the circulating sap, may, 
by the instrumentality of the vital process, be de¬ 
posited in the stem in the form of wood, or in the 
grain in that of starch.” Some of these changes may 
be performed by the chemist; he can convert 
woody fibre into starch, and starch into gum, 
though he cannot make either of these substances 
by a direct union of the elements of which they 
are composed. All he can accomplish in such at¬ 
tempts, is to change one organized substance into 
another. 
Gluten. —This is a soft, elastic substance, ob¬ 
tained by washing dough, and pressing it through a 
sieve or cloth. It is found in most kinds of grain, 
though most abundant in wheat. 
Vegetable Albumen. —This is also obtained from 
dough, and is a substance exactly resembling the 
white of an egg, having the same chemical compo¬ 
sition and the same properties. Gluten and albu¬ 
men contain the same ingredients as sugar, startb, 
&c., with the addition of nitrogen, and their fou£ 
ingredients, (carbon, hydrogen, oxygen, and nitro¬ 
gen,) are united in each in the same proportions. 
Gluten and albumen are found in the seeds of 
most kinds of grain, the former being somewhat 
more abundant. Wheat contains from 8 to 35 per 
cent, of gluten, and from 4 to 1 £ per cent, of alW 
men. These two compounds are of much value in 
food, for the reason that they contain nitrogen, an 
element which enters into the formation of muscu¬ 
lar fibre, and consequently is essential to the sup¬ 
port of every breathing creature. 
Diastase. —This is a substance not found in any 
seed nor plant, only at the time of germination, 
(sprouting,) and is therefore produced at this time, 
and aids in this process. The only part of the seed 
in which it is found, at this time, is where it is, 
connected with the sprout, and it disappears as 
soon as the shoot begins to put forth leaves. Di¬ 
astase, when separated by a chemical process, from 
its connexion with the germ and seed, is in the form 
of a white, tasteless powder. On account of tile 
difficulty of obtaining it in a pure state, it ha?> 
never been analyzed, though it is known to contain 
nitrogen. The purpose for which it is formed, at 
this particular time, is to perform a function with¬ 
out which the seed could never geripinate. 
The following description of the properties and 
action of diastase, which I copy from Johnston’s 
Agricultural Chemistry, will give you a clear view 
of its use, and the manner in which it performs its 
office. *• Diastase possesses the property of trans¬ 
forming starch entirely—first into gum and then 
into grape sugar. One part of diastase will con¬ 
vert into sugar 2,000 parts of starch. The starch 
in the seed is the food of the future germ, prepared 
and ready to minister to its wants whenever heat and 
moisture concur in awakening it to life. But starch 
is itself insoluble in water, and could not, therefore, 
accompany the fluid sap when it begins to move 
and circulate. For this reason, diastase is formed 
