NEW BORAX BEAD TECHNIC EUGENE W. BLANK Colgate-Palmolive-PeetCo., Jersey City, New Jersey
THE PRELIMINARY examination of solids before their analysis by the usual wet procedure frequently includes treatment of the substance with borax or microcosmic salt. The operation of forming a horax bead requires no explanation here.' Formation of a borax bead on the end of a platinum wire presents certain disadvantages, among which may he mentioned the inability to secure the proper color of the bead when more than one metal is present in the sample, and difficulty when but one metal is present in minute quantities or in excessive amounts. The writer prefers to use small porcelain aucibles for exact borax bead work. Size 1 to 00 Coor's porcelain aucibles are convenient. One to 2 g. of horax is melted to a clear glass on the bottom of the crucible after which several minute particles of the solid material are added to the molten horax by means of a spatula. The borax is heated to dissolve the particles and yield the color reaction. This method possesses two distinct advantages; very slight color changes are readily seen against the white
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For a concise table of borax and microcosmic bead colors see MCALPINEAND SOULE, "Qualitative chemical analysis," based D. Van Nostrand Co.. on the text by PRESCOTT AND JOHNSON, Inc., New York City, 1933, p. 590. A more detailed table is given in "The chemist's handbook," compiled and edited by the International Correspondence Schools, Seranton, Pa., 1921, p. 262.
background and, what is more important, if the material has been well distributed over the melt with considerable space between the individual particles, two or more metals may be recognized by their characteristic borax bead colors and the material under test accordingly shown to be a mixture. The color of the bead after reduction is observed by heating the aucihle and melt while a stream of illuminating gas or hydrogen is led into the crucible through a slender glass tube. A lid is used to partially close the crucible and thus maintain a reducing atmosphere over the melt. Reduction usually occurs in 5 to 10 minutes. Small quantities of borax should he used, as larger amounts scale or crack the crucible upon cooling. The method is not advocated for class instruction but rather as an aid in precise, analytical work. For transferring particles to the borax melt, a platinum wire is useful. The writer prefers a rather heavy wire attached to a glass rod by means of a '/e-inch section of rubber tubing. Such arrangement allows for the wire being removed and thoroughly cleaned by immersion in a pyrex test-tube full of molten sodium bisulfate. Scholes2 has called attention to the fact that bisnlfate fusions can be satisfactorily carried out in glass. 1
SCHOLES. G ~ SId., S 11, 237 (1930).
