332 CHEMISTRY. 



into water and carbonic anhydride, occasioned the efferves- 

 cence. The gypsum, being insoluble, is easily got rid of by 

 filtering, and then by evaporating the solution you obtain 

 the dextrin in solid form. 



455. Explanation. In this conversion of starch into dex- 

 trin the acid employed does not itself change in the least, 

 but acts only by its presence in some manner not compre- 

 hended. Starch has the composition C 18 H 30 O, 5 , and it takes 

 to itself one molecule of water, and then breaks up into 

 dextrin and glucose, a sugar about which you will learn 

 very soon. The reaction is then probably as follows : 



Starch. Water. Glucose. Dextrin. 



C 19 H 30 15 + H 3 = C 6 H 13 6 -f 2C 6 H 10 O 5 



456. Sugar. This substance is widely diffused in the 

 vegetable kingdom, though not as widely as starch. It is 

 abundant in all sweet fruits and vegetables. The Creator 

 has ordained certain plants to be great sugar-makers for 

 man, so that annually large stores of this article are laid up 

 in them for his use. The principal of these are the sugar- 

 cane, the sugar-beet, and the sugar-maple. In many fruits 

 we have an agreeable mixture of sugar with acids, the 

 chemistry of nature being competent to produce these two 

 results at the same time and in the same locality a thing 

 impossible to the chemist in his laboratory, who can only 

 obtain sugar by one process and an acid by another, and 

 then bring them together in mixture, as we so often do in 

 making lemonade. 



457. Different Kinds of Sugar. Sugar is not, like starch, 

 always one thing. There are different kinds of sugar, all 

 agreeing in being composed of the same elements carbon, 

 oxygen, and hydrogen but differing in the proportions of 

 these elements. The four most prominent kinds are as fol- 

 lows: 1. Cane-sugar, or sucrose C 12 H 22 O n found chiefly 

 in the juice of the cane, maple, and sugar-beet; 2. Milk- 



