112 MUTUAL TRANSrORMATIONS OF STARCH, :.UM, ETC. 



A further question, however, arises in our minds. We naturally ask, 

 — does nature, in thus removing one of these compounds, and supplying 

 its place by another, actually form from its elements the new substance 

 introduced, or does she produce it by a mere change or transformation 

 of those previously existing. A satisfactory reply to this question may 

 be derived from the facts detailed in the following section. 



§.6. Mutual transformations of zvoody fibre, starch, gum, and sugar. 



I. WOODY FIBRE. 



• 



1°. Action of heat. — If wood be reduced to the state of fine saw-dust, be 

 ihert boiled in water to separate everything soluble, afterwards dried by 

 a gentle heat, and then heated several limes in a baker's oven, it will be- 

 come hard and crisp, and may be ground in the mill into a fine meal. The 

 powder thus obtained is slightly yellow in colour, but has a taste and 

 smell similar to the flour of wheat; it ferments when made info a paste 

 with yeast or leaven, and when baked gives a light homogeneous bread. 

 Boiled with water, it yields a stiff tremulous jelly, like that from 

 starch (Autenrieth. — Schiibler, Agricultur Chemie, i., p. 224.) By the 

 agency of heat, therefore, it appears that the woody fibre may be changed 

 into starch. 



2°. Action of sulphuric acid. — If to tliree parts of the sulphuric acid 

 of the shops (oil of vitriol) one part of water be added, and a portion of 

 delicate woody fibre be immersed in it for half a minute, and the whole 

 then rubbed in a mortar with a few dro{)s of a solution of iodine — the 

 woody fibre will assume a blue colour, showing that it is in part at least 

 changed into starch* (Schleiden). 



Again, if three parts of fine saw-dust or of fragments of old linen be 

 rubbed in a mortar with four of the sulphuric acid of the shops added 

 by degrees — it will, in a quarter of an hotir, be rendered completely so- 

 luble in water. If the solution in water be freed from acid by chalk, and 

 then evaporated, a substance resembling gum arable is obtained (Bra- 

 connot). According to Schleiden, the fibre may be seen under the mi- 

 croscope gradually to change from without inwards, first into starch and 

 then into gum. 



Further, if this gum be digested with a second portion of sulphuric 

 acid diluted with 8 or 10 times its weight of water, it will be gradually 

 converted into grape sugar ; or the fibre of wood or linen may be changed 

 directly into sugar by the prolonged action of dilute sulphuric acid. 



3°. Action of potash. — If aaw-dust be mixed with from two to eight 

 times its weight of hydratef of potash and as much water, and boiled 

 till a crust forms on the surface, and if dilute sulphuric acid be then added 

 till the whole is slightly sour, the undestroyed woody fibre will give an 



' It will be recollected that starch is characterized by giving a blue colour with a solution of 

 iodine (see p. 107). ^ 



The simplest way of trying this experiment is, to take a quantity of clean cotton — to wet 

 it with water, squeezhig out again as much as possible — then to spread it out upon a flat dish 

 and moisten it quickly and thoroughly with the acid dihited as above. After half a minute, 

 »dd the solution of iodine, stir quickly with a glass rod, and immediately add water, when 

 the blue compound of iodine and starch will speedily deposit itself —{Schleiden, Pog. AnnaL, 

 xllii., p. 39C.) 



t Hydrate of potash is the caustic substance which is obtained by boiling common pearl- 

 »sh wiUi quick- lime. 



