Unity and diversity in the metabolism of micro - organisms 1924

the salt of the volatile acid, and the bacteria, is treated with a known uantity of normal hydrochloric aci 3 and the carbon dioxide is expelled by heating. Following this, a titration with normal alkali and phenolphthaleine as indicator, shows how much calcium carbonate is produced and consequently how much of the organic salt is oxidized. After addition of a little sulfuric acid the liquid is evaporated to dryness and after Kjeldahl’s method examined for nitrogen, while in each of the materials used the rate of nitrogen is stated separately. . . . The data show that the amount of nitrogen which can be fixed in the crude culture is at most 4.9 and 2.8 mg. per gram of oxidized calcium salt, obtained respectively with calcium propionate and calcium acetate, while 2.6 mg. was fixed per gram of calcium malate, and 1.8 mg. per gram for calcium lactate. It seems that the fixation goes on more rapidly at the beginning than later in the course of the experiment, whence it follows that when little of the organic salt is used, proportionately more nitrogen is fixed than by larger amounts. . . .