58 HOW CROPS GROW. 
tion of caustic soda, and afterwards whitening the skeleton of fibers that 
remains by means of chloride of lime, (bleaching powder.) They are al- 
most pure cellulose. 
Skeletons may also be prepared by steeping vegetable matters ina mix- 
ture of chlorate of potash and dilute nitric acid for » number of days. 
Exp. 22.—To 500 cubic centimeters,* (or one pint,) of nitric acid of 
density 1.1, add 30 grams, (or one ounce,) of pulverized chlorate of pot- 
ash, and dissolve the latter by agitation. Suspend in this mixture a 
number of leaves, etc.,t and let them remain undisturbed, at a temper- 
ature not above 65° F., until they are perfectly whitened, which may re- 
quire from 10 to 20 days. The preparations of Ieaves should be floated 
out from the solutions on slips of paper, washed copiously in clear water, 
and dricd under pressure between folds of unsized paper. 
The fibers of the whiter and softer kinds of wood are now much em- 
ployed in the fubriestion of paper. For this purpose the wood is rasped 
to a coarse powder by machinery, then freed from lignin, starch, etc., 
by ahot solution of soda, and finally bleached with chloride of lime. 
The husks of maize have been successfully employed in Austria, both 
for making paper and an inferior cordage. 
Though cellulose is insoluble in, or but slightly affected 
by dilute acids and alkalies, it is dissolved or altered by 
these agents, when they are concentrated or hot. The 
result of the action of strong acids and alkalies is very 
various, according to their kind and the degree of strength 
in which they are employed. 
The stronzest nitric acid transforms cellulose into nitrocellulose, (pyrox- 
iline, gun cotton,) a body which burns explosively, und has been em- 
ployed as a substitute for gunpowder. 
Sulphuric acid ofa certain strength, by short contact with cellulose, con- 
verts it a tough, translucent substance which strongly resembles bladder 
or similar animal membranes. Paper, thus treated, becomes the vegetable 
parchment of commerce. . : 
® On subsequent pages we shall make frequent use of some of the French dec- 
imal weights and measures, for the reasons that they are much more convenient 
than the English ones, and are now almost exclusively employed in all scientific 
treatises and investigations. For small weights, the gram, abbreviated gm., 
(equal to 1514 grains, nearly}, is the customary unit. The unit of measure by vol- 
ume is the cubic centimeter, abbreviated c. c., (80 c. c. equal one fluid ounce 
nearly). Gram weights and glass measures graduated into cubic centimeters are 
furnished by all dealers in chemical apparatus. 
t Full-grown but not old leaves of the elm, maple, and maize, heads of un- 
ripe grain, slices of the stem and joints of miize, etc., may be employed to fur. 
nish skeletons that will prove valuable in the study of the structure of these 
organs, % 
“4 
