114 CHANGE OF CANE INTO GRAPE SUGAR. 



pound of acid and the same quantity of starch and water, the change 

 will be efTecled in three hours by a temperature of 230° F. This mode 

 of converting potato starch into grape sugar is said to be extensively 

 practised in France, for the purpose of subsequently fermenting the 

 sugar and converting it into brandy. 



III. GUM. 



Action of sulphuric acid. — Tf powdered gum arabic be rubbed in a 

 mortar with the sulphuric acid of the shops, a brownish solution is ob- 

 tained, which, when diluted with water and treated with chalk, yields a 

 gummy substance similar to that obtained in the same way from starch 

 and woody fibre. Prolonged digestion with diluted acid converts a por- 

 tion of this gum into sugar. — [Berzelius, Traite de Chemie, (1831), v., 

 p. 217.] 



IV. — CANE SUGAR. 



1°. Action of heat. — When crystallized cane sugar is heated to 320° 

 F. it melts, and if the temperature be raised to 360° F. it gives oflftwo 

 atoms of water and is changed into caramel. This caramel is an un- 

 crystallizable sugar, which is generally present in artificial syrups, and 

 is often of a brownish colour. It contains the elements of an atom of 

 water less than cane sugar, and is represented by Cjjj Hg Og. It is 

 not known to occur in the natural juices of plants. 



2°. Action of sulphuric acid. — When cane sugar is digested with di- 

 lute sulphuric acid, aided by a gentle heat, it is rapidly converted into 

 grape sugar. The acid of grapes (tartaric acid) and many other vege- 

 table acids produce a similar change. 



It is obvious that this conversion of cane into grape sugar can only 

 take place in the presence of water, inasmuch, as has already been 

 shown (p. 110), grape sugar contains the elements of two atoms of water 

 more than cane sugar, or 



Cane sugar. Water. Dry grape sugar. 



We may revert now to the question with which we concluded the 

 preceding section. Since these different substances are so closely allied 

 in chemical consliiution, and occur so often in connection with each 

 other in the vegetable kingdom, does nature, when her purposes demand 

 the change, actually transform them, the one into the other, in the inte- 

 rior of the plant? The answer may now be safely given, that she cer- 

 tainly does. What we can so readily perform by our rude art may be 

 still more easily effected in the living vegetable. That which is starch 

 or gum in one part of the plant, may become cane or grape sugar in 

 another, and woody fibre in a third. Thus by re-arranging the same 

 kind and quantity of the several elements, may the various and unlike 

 forms of matter which constitute the main products of vegetation be 

 readily produced. 



Still the facility is only apparent. We can assure ourselves of the 

 fact of such conversions, because we can at will induce them. But who 

 operates upon these substances in the interior of the plant? Whose 

 mind and will directs these changes — prescribing when, where, and in 



