=85. Basic Lead Acetate.=—A solution of basic lead acetate is an invaluable aid to the sugar analyst in the preparation of samples for polarimetric observation. It acts as a clarifying agent by throwing out of solution certain organic compounds and by uniting with the organic acids in solution forms an additional quantity of precipitate, and these precipitates act also mechanically in removing suspended matters from solution. The action of this reagent is therefore much more vigorous than that of alumina cream. Coloring matters are often precipitated and removed by treatment with lead acetate. It happens therefore that there are few samples of saccharine bodies whose solutions cannot be sufficiently clarified by lead acetate to permit of polarimetric observation. The reagent is most frequently employed of the following strength:[47] Boil for half an hour in one and a half liters of water 464 grams of lead acetate and 264 grams of litharge with frequent stirring. When cool, dilute with water to two liters, allow to stand until clear, and decant the solution. The specific gravity of this solution is about 1.267. In a solution of basic lead acetate of unknown strength the percentage of lead acetate may be determined from its specific gravity by the following table:[48] PERCENTAGE OF LEAD ACETATE CORRESPONDING TO DIFFERENT SPECIFIC GRAVITIES AT 15°. Percentage of Percentage of Specific gravity. lead acetate. Specific gravity. lead acetate. 1.0127 2 1.2040 28 1.0255 4 1.2211 30 1.0386 6 1.2395 32 1.0520 8 1.2579 34 1.0654 10 1.2768 36 1.0796 12 1.2966 38 1.0939 14 1.3163 40 1.1084 16 1.3376 42 1.1234 18 1.3588 44 1.1384 20 1.3810 46 1.1544 22 1.4041 48 1.1704 24 1.4271 50 1.1869 26