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JOURNAL OD CHEMICAL EDUCATION
SSPTBMBER, 1930
are rarely uniform over a system of any considerable size. The phase rule in any simple form cannot, therefore, apply. It is interesting to summarize briefly the assumptions upon which the phase rule is based and the part played by thermodynamics in the deduction of the rule from the assumptions. It is assumed that the properties of the system treated are entirely dependent on the concentration of each molecular species in each phase, the temperature, and the pressure, and are independent of the size and shape of the system, or of the time both past and future. Such an assumption excludes extensive properties, systems which are not in equilibrium, or subject to gravitational, centrifugal, electrostatic, and electro-magnetic fields as well as colloidal systems. That the concentrations of the various molecular species in the same phase are related by a law of mass action, expression for each chemical reaction may be demonstrated by the laws of thermodynamics. Moreover, thermodynamics shows that the concentration of each substance in any phase is related to its concentration in each of the other phases by a distribution equation. Literature Cited ( I ) A. FINDLAY,"The Phase Rule and I t s Applications," Longmans, Green & Co., New York City and London, 1927, 6th edition, 328 p p (2) W A S H B ~ R NScience, , 61, 49 (1925). (3) TOLXAN.J. Am. Chem. Soc., 35, 307 (1913). ( 4 ) RICE, J. Phys. Chem., 30, 189, 1680 (1926).
UNITED STATES CNIL-SERVICE EXAMINATION FOR JUNIOR PATENT EXAMINER The United States Civil-Service Commission announces an open competitive PATENTEXAMINER, a t an entrance salary of $2000 a year. examination for JUNIOR Applications must be on file with the Civil-Service Commission a t Washington, D. C.. not later than August 26, 1930. The examination is to fill vacancies in the Patent Office, Washington, D. C. I The duties are to perform elementary scientific or technical work in the enamination of applications for patents; t o see what the allrgcd inventor thinks he has produced that is new; and to see that the disclosure is complete; and to investigate the prior a r t as represented by patents already granted in the United States and various foreign countries and by the descriptions in technical literature. Competitors will be rated on physics, technics, mechanical drawings, and the optional subject or subjeds chosen. The optionals are (1) mechanical engineering, (2) physical and organic chemistry. (3) chemical engineering, (4) civil engineering, (5) electrical-engineering. French or German, or both, may also he included if desired. Qualifying in the language test increases the probability of appointment. Full information may be obtained from the United States Civil-Service Commission, Washington, D. C., or from the Secretary of the United States Civil-Service Board of Examiners a t the post office or customhouse in any city.
