194 HOW TO TEST CANE JUICE. 
but uniform results are not obtained except in a nicely 
regulated alkaline solution. Fehling’s solution is of this 
character, and is not liable to decomposition at ordinary 
temperatures. It may be prepared as follows: 
40 grammes of sulphate of copper, 160 grammes of 
neutral tartrate of potash (or 200 grammes of tartrate of 
soda) are dissolved and added to 700-800 c. ec. (cubic centi- 
meters—grammes) of caustic soda specific gravity 1:12. 
This dilute with water to 1154°5 cubic centimeters. Of 
this solution 
0-0050 grape sugar 
. ti t 7 
1 cubic centimeter { 0-0045 cane sugar 
or grains instead of grammes—and then 1 grain—0:0050 
grape sugar, without further change of calculation. And 
100 parts of grape sugar 220-5 CuO or 
95 parts of cane o — 198 Cu? O* 
Fresenius, in his late able treatise upon Quantitative 
Chemical Analysis, gives very minute directions for the 
successful application of this test, which, somewhat con- 
densed, I insert below. It will be observed that sorghum 
juice, being a mixed solution of sugars, must be subjected 
to two experiments. One portion of a given sample to 
determine the per cent. of grape sugar—and another to 
determine that of cane sugar by reducing the latter 
to the condition of grape sugar, and applying the same 
test. By subtracting the quantity of grape sugar indicated 
by the first experiment from that indicated by the second, 
we obtain the quantity of grape sugar into which the cane 
sugar was converted, and thence by a simple calculation 
the cane sugar itself, from the data given above. 
The cane juice to be tested should be a clear solution, 
prepared by precipitating with subacetate of lead, and 
* 
* Dr. Ure. 
