Phase rule and its applications - Softcover

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1904 Excerpt: ...out as an opaque mass containing the two components in close juxtaposition. The heterogeneous nature of cryohydrates can also be shown by a microscopical examination. At the cryohydric point, therefore, we are not dealing with a single solid phase, but with two solid phases, ice and salt; the cryohydric point, therefore, as already stated, is a quadruple point and represents an invariant system. Although on cooling a solution to the cryohydric point, separation of ice may occur, it will not necessarily take place; the system may become metastable. Similarly, separation of salt may not take place immediately the cryohydric point is reached. It will, therefore, be possible to follow the curves B0 and A0 beyond the quadruple point,3 which is thereby clearly seen to be the point of intersection of the solubility curve of the salt and the freezing-point curve of ice. At this point, also, the curves of the univariant systems ice--salt--vapour and ice--salt--solution intersect. Changes at the Quadruple Point.--Since the invariant system ice--salt--solution--vapour can exist only at a definite temperature, addition or withdrawal of heat must cause the disappearance of one of the phases, whereby the system will become univariant. So long as all four phases are present the temperature, pressure, and concentration of the components in the solution must remain constant. When, therefore, heat is added to or withdrawn from the system, mutually compensatory changes will take place within the system whereby the 1 Ber., 1877, 20. 2223. Sitz.-Ber. Wien. Akad., 1880, 81. II. 1058. 1 Guthrie, Phil. Mag., 1875 4, 49. 206. condition of the latter is preserved. These changes can in all cases be foreseen with the help of the theorem of van't HofF and Le Chatelier; and, after what ...