On the other hand, if the invert sugar be calculated from the quantity corresponding to the 225 milligrams of copper corresponding to e, the data will be very different from those given above. In this instance of the levulose found corresponding to 225 milligrams of copper, viz., 133.89, 53.15 milligrams are due to the inverted sucrose. Then the quantity due to the invert sugar at first present is 133.89 - 53.15 = 80.74 milligrams. Since half the weight of invert sugar is levulose, the total weight of the invert sugar at first present is 161.48, leaving only 8.91 milligrams due to added dextrose. The difficulties in these calculations doubtless arise from the imperfect destruction of the levulose, and from variations in the reducing action of sugars on copper salts in the presence of such large quantities of sodium chlorid.
250. Calculation from Data obtained with Copper Carbonate.—The wide variations observed in different methods of calculations in the preceding paragraph, are due in part to the different degrees of oxidation exerted on alkaline copper tartrate by the dextrose and levulose. Better results are obtained by conducting the analytical work with Ost’s modification of Soldaini’s solution ([128]).
The relative quantities of levulose and dextrose oxidized by this solution are almost identical, and the calculations, therefore, result in nearly the same data, whether made from the numbers obtained with the residual dextrose or from the levulose destroyed. The method of applying this method is illustrated in the following calculation.
Example.—In a mixture of sucrose, invert sugar, and dextrose, the quantities of copper obtained by using the copper carbonate solution were as follows:
| Copper | obtained | before | inversion | = a = | 150 | milligrams. |
| ” | ” | after | ” | = b = | 250 | ” |
| ” | ” | ” | destroying lev’e | = d = | 137.5 | ” |
| ” | equivalent | to | inverted sucrose | = b - a = c = | 100 | ” |
| ” | ” | ” | levulose | = b - d = e = | 112.5 | ” |
| a = | 150 | milligrams | Cu | = |  | 44.0 | milligrams | invert sugar |
| 45.3 | ” | dextrose | ||||||
| 42.5 | ” | levulose. | ||||||
| d = | 137.5 | ” | ” | = | 41.55 | ” | dextrose. | |
| c = | 100 | ” | ” | = | 29.5 | ” | invert sugar | |
| = 28.025 | sucrose. | |||||||
| e = | 112.5 | ” | ” | = | 31.9 | ” | levulose. | |
| 14.75 | milligrams | of | dextrose = | 48.5 | milligrams | Cu. |
| 14.75 | ” | ” | levulose = | 51.5 | ” | ” |
137.5 - 48.5 = 89.0 milligrams Cu due to dextrose present before inversion.
| 150.0 - | 89.0 | milligrams | Cu | = 27 | milligrams | dextrose before inversion. |
| 89.0 | ” | ” | = 61.0 | ” | Cu due to levulose present before inversion. | |
| 61.0 | ” | ” | = 17.8 | ” | levulose before inversion. |
| 17.8 × 2 = | 35.6 | milligrams | invert sugar | present | before | inversion. |
| 27.0 - 17.8 = | 9.2 | ” | dextrose | ” | ” | ” |