VARIETIES AND CONSTITUTION OF SUGAR. 109 



In these analyses, as in those of starch and woody fihre, we see lliat 

 the per centage of oxygen is equal to that of the hydrogen multiplied by 

 8, and consequently that these two elements are, as already stated, in 

 the proportion to form water. But we see also that the carbon is in tlie 

 proportion of 12 atoms or equivalents to 10 of each of the other con- 

 stituents, and therefore gum may be represented by Cj2 Hj g Oj „ — a 

 formula which is identical with that already given for starch and cellu- 

 lar fibre. 



It appears, therefore, that not only may gum, starch, and cellular Jibre be 

 represented by carbon and water, but that they all consist of carbon and 

 the elements of water, united together in the sarne jtroportions. 



Gum not only exists in many seeds, and exudes as a natural product 

 from the stems and twigs of many trees, but is also contained in the 

 juices of many other trees, from which it is not known to exude ; and in 

 the sap of most plants it may be detected in greater or less quantity. It 

 may be considered, indeed, as one of those substances which are pro- 

 duced most largely and most abundantly in the vegetable kingdom, 

 since, as will hereafter appear, it is one of those forms of combination 

 through which organic matter passes in the interesting series of changes 

 it undergoes during the development and growth of the plant. 



§ 4. Of Sugar — its varieties and chemical constitution. 



1°. Cane Sugar. — Sugar, identical in constitution and properties with 

 that obtained from the sugar-cane, and generally known by the name of 

 cane-sugar, exists in the juices of many trees, plants, and roots. In the 

 United States of North America the juice of the maple tree is extensive- 

 ly collected in spring, and when boiled down yields an abundant supply 

 of sugar. In the Caucasus that of the walnut is extracted for the same 

 purpose. The juice of the birch also contains sugar, and it may be ob- 

 tained, in lesser quantity, from the sap of many other trees. In the 

 juice of the turnip, carrot, and beet, it is also present, and in France and 

 Germany the latter root is extensively cultivated for the manufacture of 

 beet sugar. In the unripe grains of corn, at the base of the flowers of 

 many grasses and clovers when in blossom, and even in many small 

 roots, as in that of the quicken or couch-grass (triticum repens), the pre- 

 sence of sugar may likewise be readily detected. 



Sugar is principally distinguished by its agreeable sweet taste. 

 When pure, it is colourless and free from smell. It dissolves readily 

 in alcohol and in large quantity in water. The solution in water, when 

 much sugar is present, has an oily consistence, and is known by the name 

 of syrup. From this syrup the sugar gradually deposits itself in the 

 form of sugar candy. If the syrup be boiled on too hot a fire, it chars 

 slightly, becomes discoloured, and a quantity of molasses is formed. 

 Pure cane-sugar, free from water, consists of 



Carbon . . . 44-92 per cent., or 12 atoms. 

 Hydrogen . . 6-11 " or 10 " 



Oxygen . . . 48-97 " or 10 " 



100 

 If we compare these numbers with those given for starch and gum in 

 the preceding sections, we see that they are almost identical — so that 



