The chemistry of plant and animal life . er. The flask is immersedin a water-bath heated by a gasburner, the ether is volatilized,and the vapor passes throughopenings 2 and 4 into the con-denser where it is cooled andfalls back in drops from point 4on the substance at 5. Theether percolates through the sub-stance and returns to the fats and ether-soluble mat-ters are not volatilized but remainin the flask while the ether isvaporized and condensed againand again. After the extractionis completed, the ether is distilledfrom the flask, the ether extractdried and weighed, and the per-cen
The chemistry of plant and animal life . er. The flask is immersedin a water-bath heated by a gasburner, the ether is volatilized,and the vapor passes throughopenings 2 and 4 into the con-denser where it is cooled andfalls back in drops from point 4on the substance at 5. Theether percolates through the sub-stance and returns to the fats and ether-soluble mat-ters are not volatilized but remainin the flask while the ether isvaporized and condensed againand again. After the extractionis completed, the ether is distilledfrom the flask, the ether extractdried and weighed, and the per-centage amount calculated. Whilethe process appears to be simple,it is a difficult operation to con-trol, because even after many-days extraction, some materialswill continue to give up etherextract, and unless unusual careFig. 79.—Ether extractor. is taken somc of the fats areoxidized. Then, too, the ether extract is liable to becontaminated with impurities if ether of a high degreeof purity is not used. When the determinations are made. ORGANIC COMPOUNDS OP PLANTS 205 under uniform conditions, the results are comparable andare of value when properly interpreted. Organic Acids273. Occurrence in Plants.—In all plants and vege-table foods, there are present bodies known as organicacids. An organic acid, like all acids, contains hydrogenwhich can be replaced by a metal (see Section 75). Thenegative radical of the acid contains carbon, hydrogen,and oxygen. For example, in tartaric acid, H^C^H^Og,the H2 can be replaced by a metal; C^HjOg is the tartaricacid radical. Organic acids, like mineral acids, areneutralized by bases. Tartaric Potassium 3,010 2KOH + H^QH^Og = K,C,H A -f 2H, a rule, the organic acids are not present in a freestate, but are combined with base-forming elements, aspotassium and calcium, forming organic and acid plants, the organic acids are found mainly in solution,as in the sap. When the plant matures, they are usedeither for the constr
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