JOURNAL OF CHEMICAL EDUCATION
SODIUM PERCHLORATE AND ANHYDROUS MAGNESIUM SULFATE: TWO STUDENT PREPARATIONS SIGTRED PETERSON University of Louisville, Louisville, Kentucky
Because of its use in studying (or compensating for) salt effects,sodium perchlorate is an important research chemical. However, because of the lack of standards it is not commercially available in sufficient purity. The high solubility of the salt makes its isolation a good exercise in crystallization of a soluble salt. A somewhat differentpreparation of this salt has been suggested in a recent textbook.' To about 40 g. of solid sodium carbonate ip slowly added a few ml. short of the equivalent 70 per cent perchloric acid. During addition of the remaining acid the solution is tested on a spot plate with methyl orange to determine the equivalence point and boiled to expel carbon dioxide. The solution is then evaporated if necessary to near saturation, filtered, and cooled with ice to crystallize the product. An additional crop of crystals can be obtained by adding alcohol (ethyl or isopropyl) to the mother liquor. To use this method to prepare sodium perchlorate of strict purity for research requires reagent grade chemicals. However, 0.1-g. samples of student products made bv this method, even usine technical soda ash. FIESEE,L. F., "Experiments in Organic Chemistry," 2nd ed., seldom show chloride'or sulfate impurity. The com: D. C.' Heath and Company, New York, 1941, p. .37; ADKIXS, monest impurity found is bicarbonate, present because the student, duly warned of the dangers of boiling AND M. W. KLEIN,"Practice of OrHOMER,S. M. MCELVAIN, ganic Chemistry," 3rd ed., McGraw-Hill Book Company, New perchloric acid, carefully avoids even a small excess of G . R., "Lahoratory Practice of acid in his solution. Simple qualitative tests for anions York, 1940, p. 147; ROBERTSON, Organic Chemistry," Fkvised edition, The Macmillan Company, make the quality of student products easily judged by New York, 1943, pp. 109 and 159. K o z o m w AND ~ MITSUIKOZANKABUSHIKI KAISIU,Japanese the instructor.
Two chemicals useful in research have been prepared as student exercises in inorganic preparations. While both are merely variations of the preparation of a salt from an acid and a base, each involves sufficientexercise of technique to be a challenge to the student. Powdered anhydrous magnesium sulfate has been suggested as a drying agent for organic liquids' and, mixed with porous materials, for gases.2 I t is usually prepared' by drying and pulverizing Epsom salt. The product of the following method has been found a convenient and useful drying agent in organic research in this department. To powdered magnesium oxideain a large evaporating dish, concentrated sulfuric acid is slowly added, being stirred in with a pestle. Somewhat less than the calculated equivalent of acid should be used since an excess of acid in the product diminishes its usefulness. The reaction mixture becomes sufficiently hot to drive out the water produced. The final product is a free-flowing powder which does not give an acid reaction with litmus paper (or better, nitrazine paper). The size of the evaporating dishes available imits the scale of the ma.ct,ion.
Patent 89,593. 8 The magnesium oxide used was U. S. P. XII, heavy grade, made by the New York Quinine and Chemical Works, Inc.
WALTON,H. F., "Inorganic Preparations," Prentice-Hall, Inc., New York, 1948, pp. 72-73.
