MM. Cailletet, Wroblewski, and Olzewski have continued their experiments in liquefaction, and acquired increased facility in the handling of liquid ethylene, formene, atmospheric air, oxygen, and nitrogen. M. Olzewski was able to report to the French Academy of Sciences, on the 21st of July, 1884, that by placing liquefied nitrogen in a vacuum he had succeeded in producing a temperature of -213°C. (-351° Fahr.), under which hydrogen was liquefied. Contrary to the suppositions founded on the metallic behavior of this element, that it would present the appearance of a molten metal, like mercury, the liquid had the mobile behavior and the transparency of the hydrocarbons. * * * * * EXAMINATION OF FATS. The methods employed up to the present in examination of fats, animal and vegetable, are mere reactions lacking general application; scattered throughout the literature, and doubtful with regard to reliability, they are of little or no value to the experimenter--an approximate quantitative examination even of a simple mixture being exceedingly difficult if not impossible, since the qualitative composition of fatty substances is the same, and the separation of the nearer components impracticable. The object of analysis consisted in estimating the accompanying impurities of fat, as, resin, albuminoids, and pigments. The nature of these substances depends on the mode of extraction and preservation of the fat, and are subject in the course of time to alteration. The only reaction based upon the chemical constitution of fat is produced by treatment of oleic or linoleic acid with nitrous acid, which therefore is of some value in the examination of drying oils. Of general application are the methods which correspond to the chemical constitution of fats, and thus determine the relative quantity of the components; advantage can then be derived from qualitative reactions, inasmuch as they further affirm the result of the quantitative test, or dispel any doubt with regard to the correctness of the result. The principal methods which comply with these demands have been carefully studied by Hueble for the purpose of discovering a process of general application; methods founded on the determination of density, freezing, and melting point were compared with those dependent on the solubility of fatty substances in glacial acetic acid or a mixture of alcohol and acetic acid; also the method of Hehner for testing of butter, the determination of glycerine and oleic acid, and at length the process of saponification. Nearly all fats contain members belonging to one of the three series of fatty acids, _e.g._, acids of the type of acetic acid (stearic and palmitic acids); such as are derivatives of acrylic acid (oleic and erucic acids); and such as are homologues of tetrolic acid (linoleic acid). It is likely that the relative quantity of each of these acids is variable, with regard to the same fat, within definite limits,