Since the paragraphs relating to these processes were printed some important improvements in the preparation of the alkaline copper solutions have been made. The copper carbonate solution, as has already been said, is peculiarly suited to the determination of reducing sugars in the presence of sucrose and the modified forms of this solution, and the methods of employing them with invert sugar, dextrose, levulose, and maltose, are described below. =233. Estimation of Minute Quantities of Invert Sugar in Mixtures.=—The method of Hiller and Meissl, paragraph =142=, may be used for the estimation of small quantities of invert sugar in mixtures. A modified form of Soldaini’s reagent is, however, to be preferred for this purpose. Ost has proposed and tested a copper carbonate solution for the purpose mentioned which gives reliable results.[189] The solution has the following composition: One liter contains 3.6 grams crystallized copper sulfate. 250.0 ” potassium carbonate. 100.0 ” hydrogen potassium sulfate. This reagent undergoes no change when kept for a long while, especially in large vessels. Even in smaller vessels it can be kept for a year or more without undergoing any change. The method of analysis is the same as that described in paragraph =128=, with the exception that the boiling is continued for only five minutes instead of ten, and the quantities of the copper and sugar solutions used are doubled, being 100 and fifty cubic centimeters respectively. In no case must the solution used contain more than thirty-eight milligrams of invert sugar. The quantity of sucrose in the mixture is obtained by polarization (=94=). Ost has also recalculated the reduction values of the common sugars for the strong copper carbonate solution, and the numbers obtained are slightly different from those given on page 142.[190] For different percentages of invert sugar in mixtures of sucrose, the quantities of invert sugar are calculated from the number of milligrams of copper obtained by the following table: (A) = Milligrams of copper obtained. (B) = Pure invert sugar. (C) = Invert sugar. (D) = Sucrose.