=249. Calculation of Results.=—If we represent by a the weight of metallic copper reduced by the invert sugar present in a solution containing sucrose, and by _b_ that obtained after the inversion of the sucrose, the quantity of copper corresponding to the sucrose is _b - a_ = _c_. After the destruction of the levulose, the copper reduced by the residual dextrose may be represented by _d_. The weight of copper equivalent to the levulose is, therefore, _b - d_ = _e_. From the tables already given, the corresponding quantities of the sugars equivalent to _c, d_, and _e_ are directly taken. Example: { 163.8 milligrams invert sugar. _a_ = 300 milligrams = { 156.5 ” dextrose. { 185.63 ” levulose. _b_ = 500 ” _d_ = 275 ” = 142.8 ” dextrose. _c_ = 200 ” = 106.3 ” invert sugar. _e_ = 225 ” = 133.89 ” levulose. The 106.3 milligrams of invert sugar equivalent to _c_, correspond to 101 milligrams of sucrose. The quantity of dextrose equivalent to 275 milligrams of copper is 142.8. Of this amount 53.15 milligrams are due to the inverted sucrose, leaving 89.65 milligrams arising from the invert sugar and dextrose originally present. This quantity is equivalent to 175 milligrams of copper. Of the 300 milligrams of copper obtained in the first instance, 125 are due to levulose in the original sample, corresponding to 69.73 milligrams which number, multiplied by two, gives the invert sugar present. The sample examined, therefore, had the following composition: Sucrose 101.00 milligrams. Invert sugar 139.46 ” Dextrose 19.92 ” ------ Sum 260.38 ” 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.