=139. Tables for Use in the Gravimetric Determination of Reducing Sugars.=—The value of a table for computing the percentage of a reducing sugar present in a solution, is based on the accuracy with which the directions for the determination are followed. The solution must be of the proper strength and made in the way directed. The degree of dilution prescribed must be scrupulously preserved and the methods of boiling during reduction and washing the reduced copper, followed. The quantity of copper obtained by the use of different alkaline copper solutions and of sugar solutions of a strength different from that allowed by the fixed limits, is not a safe factor for computation. It must be understood, therefore, that in the use of the tables the directions which are given are to be followed in every particular. =140. Allihn’s Gravimetric Method for the Determination of Dextrose.=—_Reagents_: I. 34.639 grams of CuSO₄.5H₂O, dissolved in water and diluted to half a liter: II. 173 grams of rochelle salts } dissolved in water and diluted 125 grams of KOH, } to half a liter. _Manipulation_: Place thirty cubic centimeters of the copper solution (I), thirty cubic centimeters of the alkaline tartrate solution (II), and sixty cubic centimeters of water in a beaker and heat to boiling. Add twenty-five cubic centimeters of the solution of the material to be examined, which must be so prepared as not to contain more than one per cent of dextrose, and boil for two minutes. Filter immediately after adding an equal volume of recently boiled cold water and obtain the weight of copper by one of the gravimetric methods given. The corresponding weight of dextrose is found by the following table: ALLIHN’S TABLE FOR THE DETERMINATION OF DEXTROSE. (A) = Milligrams of copper. (B) = Milligrams of dextrose.