The calculations made from the later data (=234=) give almost the same results. =251. Winter’s Process.=—Winter has proposed a method of separating dextrose and levulose in the presence of sucrose based on the selective precipitation produced on treating mixtures of these sugars in solution with ammoniacal lead acetate.[206] The reagent is prepared immediately before use by adding ammonia to a solution of lead acetate until the opalescence which is at first produced just disappears. The separation is based on the fact that the compound of sucrose with the reagent is easily soluble in water, while the salts formed with levulose and dextrose are insoluble. The separation of the sugars is accomplished as follows: The ammoniacal lead acetate is added to the solution of the mixed sugars until no further precipitate is produced. The precipitated matters are digested with a large excess of water and finally separated by filtration. The sucrose is found in the filtrate in the form of a soluble lead compound, from which it is liberated by treatment with carbon dioxid. The lead carbonate produced is separated by filtration and the sucrose is estimated in an aliquot part of the filtrate by optical or chemical methods. The precipitate containing the lead compounds of dextrose and levulose is washed free of sucrose, suspended in water and saturated with carbon dioxid. By this treatment the lead compound with dextrose is decomposed and, on filtration, the dextrose will be found in the filtrate, while the lead compound of the levulose is retained upon the filter with the lead carbonate. After well washing the precipitate, it is again suspended in water and saturated with hydrogen sulfid. By this treatment the lead levulosate compound is broken up and the levulose obtained, on subsequent filtration, in the filtrate. The dextrose and levulose, after separation as above described, may be determined in aliquot parts of their respective filtrates by the usual gravimetric methods. Before determining the levulose the solution should be heated until all excess of hydrogen sulfid is expelled. This method was used especially by Winter in separating the various sugars obtained in the juices of sugar cane. It has not been largely adopted as a laboratory method, and on account of the time and trouble required for its conduct, is not likely to assume any very great practical importance. =252. Separation of Sugars by Lead Oxid.=—In addition to the combination with the earthy bases, sugar forms well defined compounds with lead oxid. One of these compounds is of such a nature as to have considerable analytical and technical value. Its composition and the method of preparing it have been pointed out by Kassner.[207]