FEHLING’S SOLUTION. 193 
of alcohol, and let it remain a week longer. If the juice 
is of good quality, crystallization will rapidly ensue at the 
first, the whole mass of syrup becoming solidified ap- 
parently into crystals of cane sugar. If the proportion of 
unerystallizable sugar is large, crystallization will be re- 
tarded, and if the experiment was made upon the juice of 
impure or very unripe cane, it will refuse to crystallize at all. 
When the whole mass has become solid with crystals, 
-place it in a bottle, after breaking it up into fragments, and 
pour upon it four or five times its volume of anhydrous 
alcohol, digest in a water-bath for half an hour or more, 
meanwhile shaking the bottle repeatedly. Afterwards let 
it remain at rest for several hours, and then decant the 
clear solution. Repeat this washing with alcohol once or 
twice, then dry the undissolved sugar contained in the bottle, 
over boiling water, and weigh it. The loss in weight is the 
amount of uncrystallizable sugar dissolved by the alcohol. 
The practical sugar maker may find it inconvenient, or 
unnecessary to his purpose to continue the experiment far- 
ther than to discover to what extent the sugar is crystal- 
lizable. 
Other and more intricate methods, leading to more im- 
mediate and accurate results, will commend themselves to 
those whose opportunities and acquirements befit them for 
the task of conducting them with success. 
1. Tue Copper Test. Fehling’s. Solution. — This 
method depends upon the property possessed by grape or 
fruit sugar—but not by cane sugar—of reducing to the state 
of suboxide the hydrated protoxide of copper when the 
latter is presented to it in an alkaline solution, and the 
temperature of the mixture is elevated tothe boiling 
point. The quantity of the oxide of copper reduced is 
proportional to the quantity of grape sugar in the solution, 
17 
