110 CANE, GRAIE, MANNA, AND LIQUORICE SUGARS. 



cane-sugar also contains oxygen and hydrogen in the proportions to form 

 water, and may likewise be represented by the formula C,2 H^,, Ojo* 



2°. Grape sugar. — In the juice of the grape a peculiar species of su- 

 gar exists, which, in the dried raisin, j)resents itself in the form of little 

 rounded grains. The same kind of sugar gives their sweetness to the 

 gooseberry, the currant, tlie apple, pear, plum, apricot, and most other 

 fruits. It is also the sweet substance of the chesnut, of the brewers' 

 wort, and of all fermented liquors, and it is the solid sugar which floats 

 in rounded grains in liquid honey, and which increases in apparent 

 quantity as tlie honey, by keeping, becomes more and more sohd. 



Grape sugar has nearly all the sensible characters of cane sugar, with 

 the exception of being less soluble in wafer and also less sweet, — 2 parts- 

 of the latter imparting an equal sweetness with 5 of the former. 



In chemical constitution they differ considerably. Thus grape sugai 

 dried at 250° F., consists of 



Carbon . . . 40-47 per cent., or 12 atoms. 

 Hydrogen . . 6-59 " or 12 " 



Oxygen . . . 52-94 " or 12 " 



100 



The oxygen here is still eight times greater than the hydrogen, and^ 

 therefore, in this variety of sugar also, these elements exist in the pro- 

 portioru", to form water. But for every 12 equivalents of carbon, dry 

 grape sugar contains 12 of hydrogen and 12 of oxygen. It is conse- 

 quently represented by C12 Hjg Ojo, and contains the elements of two 

 atoms of water (Hg Oo) more than cane sugar.* 



3°. Manna sugar, sugar of liquorice, Sfc. — Besides the cane and grape 

 sugars which occur in large quantity in the juices of plants, there are 

 other varieties which occur less abundantly, and are therefore of less in- 

 terest in the study of the general vegetation of the globe. Among these 

 is manna, which partly exudes and is partly obtained by incisions from 

 certain species of the ash tree which grow in the warmer countries of 

 Southern Europe (Sicily and Italy), and in Syria and Arabia. It also 

 exists, it is said, in the juice of the larch tree, of common celery, and of 

 certain trees which are met with in New South Wales. Liquorice root 

 also contains a species of hiack sugar, which is known in this country 

 under the names of Spanish and Italian juice, from the countries where 

 it is grown. In the mushroom and oi\\er fungi a colourless variety, ap- 

 parently peculiar, has also been met with,— and milk owes its sweet- 

 ness to a species of sugar formed in the interior of the animal along with 

 the other substances which the milk contains. 



These several kinds of sugar differ more or less, not only in sensible 

 and chemical properties, but also in chemical constitution, from llie more 

 abundant cane and grape sugars — but they form too smalJ a part of the 

 general products of vegetation, and are of too little consequence in practi- 



* Solutions of cane and grape sugar are readily distinguished from each other by the fol- 

 lowing chemical characters :— 1. If the solution be heated and a few drops of sulphuric acid 

 then added, cane sugar will be decomposed, blackened, and made to fall as a black or brown 

 powder— while a solution of grape sugar will at tlie most be only slightly discoloured. 2. If, 

 instead of sulphuric acid, caustic potash be employed, the cane sugar will be unchanged, 

 wliile the grape sugar will be blackened and thrown down. 



