=157. Precipitation with Phloroglucin.=—Instead of using pyrogalol for the precipitating reagent phloroglucin may be employed. The method of procedure proposed by Councler for this purpose is given below.[131] The furfurol is prepared by distillation in the usual way. The volume of the distillate obtained is completed to half a liter with twelve per cent hydrochloric acid, and an aliquot portion, varying in volume with the percentage of furfurol is withdrawn for precipitation. This portion is placed in a glass-stoppered flask with about twice the quantity of finely powdered phloroglucin necessary to combine with the furfurol present. The contents of the flask are well shaken and allowed to stand fifteen hours. The precipitate is collected on an asbestos filter, washed free of chlorin, dried at the temperature of boiling water and weighed. The theoretical quantity of precipitate corresponding to one part of furfurol, _viz._, 2.22 parts, is never obtained since the precipitate is not wholly insoluble in water. The actual proportions between the precipitate and the original furfurol vary with the amount of precipitate obtained. When the weight of the precipitate is 200 milligrams and over, 2.12 parts correspond to one part of furfurol. When the weight of the precipitate varies from fifty to 100 milligrams, the ratio is as 2.05:1 and when only about twenty-five milligrams of precipitate are obtained the ratio is as 1.98:1. The quantity of pentose bodies corresponding to the furfurol is calculated from the factors given by Tollens in a preceding paragraph. The reaction which takes place with furfurol and phloroglucin is simply a condensation of the reagents with the separation of water. It is very nearly represented by the following formula: 2C₅H₄O₂ + C₆H₆O₃ = C₁₆H₁₂O₆ + H₂O. Furfurol. Phloroglucin Condensation Water. product.