Spectrographic Determination of Small Amounts OF Tungsten in Steel PHILIP FISCHER, ROBERT SPIERS, AND PHILIP LISAN, Tort Laboratory, United States Navy Yard, Philadelphia, Pa. the residue. Warm an a stPam bath for a few minutes, then filter through a dry No.40 \\'hatman 9.0-cm. paper. MOnlFlED C n p X l r ~ L h O C E D I I i W \\'HES C O L l r l l B l u M IS PRRS~ m .1)iswlve a 2.gram suniplc in a covered 25&ml. beaker with 10 ml. of hydroclilorir u d (sp. pr. l.l9),5 ml. of phosphoric acid (837J, and 3Oml. of pervhlorir arid (?Ow0). Hear "vera low Eame until the mmnlc is CO~LII,IC~CIV . "dissolved. Continue 85 in chemical procedure.'
Accurate determinations 01 0.01 to 0.25% 01tungsten in steels were made by a combined spectrochemical method. The tungsten was separated by a variation ol Knowlos' method and then determined spectrographically. A modified chemical procedure lor reparating dl the columbium from tungsten was developed in order to determine the tungsten spectrographically. A high degree 01 reproducibility was obtained bv carbon electrodes impregnated with the . rDarkins . . tungsten solution.
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SPECTROGRAPHIC PROCEDURE
The carbon electrodQs used in the Jpertrogra~ihieprorrdure are preparcd by henring graphitic rods 0.7X X 30 rm. (6/t. X 12 inches). in II muffle a1 510' C. for I hour. After coolins. the rods are cut into 5-cm. (%inch) lengths on an alundum c;tting wheel (IC). Hcfore using, the ends.6f theelcctro~lrsarep~lishcd with a fine Glc. One drop of tlic solution, prepared hy the above rlieinirnl oruccdure. is vlarrd on ~ a r hof IWO Eat 101)carbon electrodes: which are sparked immediately after ahsGption of the solution. A Bausoh & Lomh medium quart5 spectrograph is used with an uncontrolled, condensed spark source, rated a t 13,500 volts. The optical stand is placed 45 em. (18 inches) from the slit. An exvosure of 60 seconds with no condensing lens or pre-spark is rccdnl+d on ,an Eaatman :
