76 HOW CROPS GROW. 
water. Observe that the saccharose and dextrin suffer no alteration for 
a long time, while the glucose and molasses shortly cause the separation 
of suboxide of copper. 
Exp. 32.—Heat to boiling a little white cane-sugar with 30c. e. of 
water, and 8 drops of strong sulphuric acid, in a glass or porcelain dish, 
for 15 ninutes, supplying the waste of water as needful, and test the 
Uguid as in the last Exp. It will be found that this treatment trans- 
forms saccharose into glucose, (and levulose.) 
The quantit tive estimation of the sugars and of starch is commonly 
based upon the reaction just described. For this purpose the alkaline 
copper solution is made of a known strength by dissolving a given weight 
of sulphate of copper, etc., in a given volume of water, and the glucose, 
or levulose, or a mixture of both, being likewise made to a known yol- 
ume of solution, it is allowed to flow slowly from a graduated tube into 
a measured portion of warm copper solution, until the blue color is dis- 
charged. Experiment has demonstrated that one part of glucose or 
of levulose reduces 2.205 + parts of oxide of copper. Starch and sac- 
charose are first converted into glucose and levulose, by heating with an 
acid, and then examined in the same manner. For the details required 
to ensure accuracy, consult Fresenius’ Quantiiiive Analysis. 
As already stated, cane-sugar, by long boiling of its 
aqueous solution, and under the influence of hot dilute 
acids (Exp. 32) and yeast, loses its property of ready erys- 
tallization, and is converted into levulose and glucose. 
According to Dubrunfaut, two molecules of cane-sugar take up the 
elements of two molecules, (5.26 per cent,) of water, yielding a mixture 
of equal parts of levulose and glucose. This change is expressed in 
chemical symbols as follows: 
2 (Cio Ho O11.) + 2H20 = Cy Hy Org + Cig Hos Ore 
Oune-sugar. Water. Levulose. Glucose. 
The alterability of saccharose on heating its solutions 
occasions a loss of one-third to one-half of what is really 
contained in cane-juice, and is one reason that solid sugar 
is obtained from the sorghum with such difficulty. Mo- 
lasses, sorghum syrup, and honey, usually contain all three 
of these sugars. In molasses, both the saccharose and 
glucose are hindered from crystallization by the levulose, 
and by saline matters derived from the cane-juice. 
Honey-dew, that sometimes falls in viscid drops from 
the leaves of the lime and other trees, is essentially a mix- 
