The Preparation of Magnesium Nitride A laboratory Experiment
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F. FROMM end PEDRO JOSE RIVERA Polytechnic Institute of Puerto Rim, San Germ&, Pwrto Rieo
ABORATORY instruction in chemistry is not only a process of teaching but with the accumulation of experience by many groups of students it leads to modifications of standard processes which seem worth recording. The heating of magnesium powder in a tightly closed crucible has been suggested as a way of obtaining magnesium nitride ( 1 , 2 ) . The yield is always low and the product impure because part of the metal combines with the oxygen of the air left in the crucible. Very often, however, no nitride a t all will be obtained because the oxidation is so rapid and violent as to lift the lid of the crucible and to produce fireworks. Magnesium nitride has been prepared by Miner (3) from magnesium oxide by simultaneous action of carbon and elementary nitrogen. Lafitte, Elchardus, and Grandadam (4) used the interaction of ammonia and metallic magnesium and the direct union of the elements (4, 5 ) . The apparatus applied by all these authors is rather complicated and entirely unfit for use in the undergraduate laboratory, but it can easily be simplified. The direct synthesis was considered the most convenient preparation. Nitrogen was produced from ammonium nitrite. The well-dried gas was passed through a hard-glass tube containing a porcelain boat with magnesium powder. The metallic powder was heated with a Bunsen burner until the whole material turned yellow. The union of the elements takes place between 300' and 700" in the course of a few hours, provided that the reacting agents are well dried. Traces of moisture will a t once produce magnesium oxide. The passage of the gas through two washing bottles with concentrated sulfuric acid was not sufficient for drying the gas; i t was necessary to conduct the gas through two washing bottles with concen-
trated sulfuric acid and three soda lime tubes (30 cm. long, 1.5-cm. diameter, each). From 0.2 to 0.5 g. of the powdered metal was heated in a constant flow of nitrogen and the reaction was completed in about two hours. The yellow nitride was cooled in flowing nitrogen. The yield was always less than expected and ranged from GO to 90 per cent. The purity of the product was determined by alkaline hydrolysis in a Kjeldahl apparatus, and showed that the sample consisted of 99 per cent of magnesium nitride. An explanation of the low yield was found in the fact that the magnesium powder was partially oxidized. Though magnesium oxide as such does not react with nitrogen under the conditions given, a mixture of 0.1946 g. magnesium powder with 0.0973 g. magnesium oxide powder was easily nitrified, giving 0.3103 g. of the yellow product, or 91 per cent of the theoretical yield. Analysis showed 95.8 per cent MgsN,; most of the oxide had been converted into mamesium nitride. Commercial magnesium powder, containing some magnesium oxide, will yield a satisfactory product if pro$erly treated; for highest purity metallic powder free from oxides ought to be used.
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LITERATTRE CITED
(1) B E N E D I "Chemical ~. Lecture Experiments," The Macmillsn Company. New York. 1935, p. 375. (2) HENDERSON AND FERNELIUS, "A Course in Inorganic Preparations," McGraw-Hill Book Company, Inc.. New York. 1935, pp. 60-1. (3) M ~ N E R"Process , of producing nitrides of aluminum or m a d s i u m from their minerals." U. S. Patent 1.803.720
SUMMER PROGRAM. UNIVERSITY OF PtlTSRlTRGH
TO ENABLE graduates of high ~ h o o l to s advance themselves a full year in chemistry in connection with the wax emergency, the University of Pittsburgh will offer an eight-credit course in General Chemistry during eight weeks from June 26 to August 19. To enable college and university students to advance similady, an eight-week course in organic chemistry will be offered for eight credits. Also bezinning June 26, lZweek (full-semester) courses will
be offered in inorganic, analytical. organic, and physical chemistry, and graduate courses in the fields of advanced organic (type reactions and microanalysis) and physical chemistry, enzymes, and kinetics. A special course covering "Rerent Developments in Theoretical and Applied Chemistry" will be given far instructors in preparatory schools. Only full-time regular staff members will he in charge.
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