Here, however, we are not so much interested in manufactures of cellulose itself, that is, wood, paper and cotton, as we are in its chemical derivatives.  Cellulose, as we can see from the symbol, C_{6}H_{10}O_{5}, is composed of the three elements of carbon, hydrogen and oxygen.  These are present in the same proportion as in starch (C_{6}H_{10}O_{5}), while glucose or grape sugar (C_{6}H_{12}O_{6}) has one molecule of water more.  But glucose is soluble in cold water and starch is soluble in hot, while cellulose is soluble in neither.  Consequently cellulose cannot serve us for food, although some of the vegetarian animals, notably the goat, have a digestive apparatus that can handle it.  In Finland and Germany birch wood pulp and straw were used not only as an ingredient of cattle food but also put into war bread.  It is not likely, however, that the human stomach even under the pressure of famine is able to get much nutriment out of sawdust.  But by digesting with dilute acid sawdust can be transformed into sugars and these by fermentation into alcohol, so it would be possible for a man after he has read his morning paper to get drunk on it.

If the cellulose, instead of being digested a long time in dilute acid, is dipped into a solution of sulfuric acid (50 to 80 per cent.) and then washed and dried it acquires a hard, tough and translucent coating that makes it water-proof and grease-proof.  This is the “parchment paper” that has largely replaced sheepskin.  Strong alkali has a similar effect to strong acid.  In 1844 John Mercer, a Lancashire calico printer, discovered that by passing cotton cloth or yarn through a cold 30 per cent. solution of caustic soda the fiber is shortened and strengthened.  For over forty years little attention was paid to this discovery, but when it was found that if the material was stretched so that it could not shrink on drying the twisted ribbons of the cotton fiber were changed into smooth-walled cylinders like silk, the process came into general use and nowadays much that passes for silk is “mercerized” cotton.

Another step was taken when Cross of London discovered that when the mercerized cotton was treated with carbon disulfide it was dissolved to a yellow liquid.  This liquid contains the cellulose in solution as a cellulose xanthate and on acidifying or heating the cellulose is recovered in a hydrated form.  If this yellow solution of cellulose is squirted out of tubes through extremely minute holes into acidulated water, each tiny stream becomes instantly solidified into a silky thread which may be spun and woven like that ejected from the spinneret of the silkworm.  The origin of natural silk, if we think about it, rather detracts from the pleasure of wearing it, and if “he who needlessly sets foot upon a worm” is to be avoided as a friend we must hope that the advance of the artificial silk industry will be rapid enough to relieve us of the necessity of boiling thousands of baby worms in their cradles whenever we want silk stockings.