SUGAR. 359 



called dextrine, is obtained in the above process, instead 

 of sugar. It may also be prepared by roasting starch, 

 carefully, with constant stirring, until it acquires a 

 brownish yellow color. This gum is used largely in 

 calico printing, for thickening colors. It is also used in 

 making the so-called " fig-paste," and certain other 

 kinds of confectionery. The composition of starch 

 and gum is precisely the same. 



906. GUM. Gum arabic. and the sum 



What is said . . . . . 



of natural of fruit trees generally, is identical in com- 

 gum*l position with woody fibre and starch. 



They are either soluble, like gum arable, in water, or 

 swell up with it to form a thick paste, like gum traga- 

 canth. The substance called pectine, which causes 

 the juice of currants, and other fruits to stiffen with 

 sugar into a jelly, is also similar to the above sub- 

 stances in composition. All of these bodies, like wood 

 and starch, are convertible into sugar by the action of 

 sulphuric acid. 



SUGAR. 



GRAPE SUGAR - The production 

 grape sugar of this substance from wood and starch has 

 already been described. It does not exist 

 in the juice of grapes, as its name would imply. The 

 sugar of the grape and other acid fruits, contains two 

 molecules less of water. It is spontaneously converted 

 into true grape sugar or glucose, and found in incrus* 

 tat.ons upon the surface of the dried fruit. Those 

 fruits and trees which have but little acid in their 



