58 HOW CEOPS GROW. 



tion of caustic sodii, and aftorwai-ds whitening the slieleton of fibers tliat 

 remains by means of chloride of lime, (bleaching powder.) They are al- 

 most pure cellulose. 



Skeletons may also be prepared by steepinii vegetable matters in .1 mix- 

 ture of chlorate of potash and dilute nitric acid fir a number of days. 



Exp. 23.— 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 

 numbei- of leaves, etc.,t and let them remain undisturbed, at a temper- 

 ature not above 65° F., until they are perfectly whitened, wliich may re- 

 quire from 10 to 20 days. The preparations of leaves should be floated 

 out from the solutions on slips of paper, washed copiously in clear watei-, 

 and dried under pressure between folds of unsized paper. 



The iibers of the whiter and softer kinds of wood are now much em- 

 ployed in the fibrication of pi\per. For this purpose the wood is rasped 

 to a coarse powder by machinery, tlien freed from lignin, starch, etc., 

 ■ by aiiot solution of soda, and finally Ijleaelied with chloride of lime. 



The husks of maize have been successfully employed in Austria, both 

 for making paper and an iuferior 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 tlieir kind and the degree of strength 

 in which they are employed. 



The strongest nitric acid transforms cellulose into nitrocellulone, (pyrox- 

 iline, gun cotton,) a body which burns explosively, and has been em- 

 ployed as a substitute for gunpowder. 



Suljihuric acid of a 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 15i^ grains, nearly!, is the customary unit. The imitof measure by vol- 

 lune is the cubic centimeter, abbreviated c. c, (30 c. c. equal cue 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 maize, etc., may be employed to fur- 

 nish skeletons that will prove valuable in the study of the structure of these 

 organs. 



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