CHEMISTRY. 71 



These are disposed to change of elementary form whenever 

 the balance of opposing forces is destroyed: that is, whenever 

 by the agency of some external disturbing force, as heat, air or 

 water, the affinity which holds these elements together is over- 

 come, the elements are separated entirely, or one element is 

 replaced by another ; and thus lignine is changed into starch, 

 starch into sugar, &c. 



This intimate relation of composition among these substances 

 renders it plain that they may all occur together in the same 

 plant, and that when one occasionally disappears from the 

 plant, it may be replaced entirely or in part by another; and 

 this is really the case. Lignine or woody fibre may be changed 

 to starch by boiling sawdust in water so as to separate all 

 soluble matters, then drying it in an oven and fermenting with 

 yeast. In this way the author has made bread of beech wood, 

 which was but little inferior to that made from unbolted wheat 

 flour. 



Woody fibre may be transformed to starch, also, by the 

 action of sulphuric acid or caustic potash. 



Starch, when gradually heated to a temperature not ex- 

 ceeding 300 F., acquires a brownish tint, and is changed to 

 gum. Starch may be changed to gum by dissolving it in hot 

 water, and allowing it to remain in a cold place for a few 

 months ; or it may be changed more rapidly by boiling it in 

 water for a length of time. By the action of sulphuric acid, 

 also, starch may be changed to gum, and this gum again into 

 grape sugar. 



Gum arable may be changed to sugar by the agency of 

 chalk and sulphuric acid. [Berzelius. 



Cane sugar which is crystalized, if heated to a temperature 

 of 360 F., gives off two atoms of water and is changed to 

 caramel: this is an uncrystallizable sugar, containing one pro- 

 portion of oxygen and one of hydrogen less than cane sugar. 

 Cane sugar may be changed to grape sugar by digesting it in 



