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cylinder is preferred. It was necessary to bleed the cylinder at 3 to 4 ml. per minute for 2 to 3 days before good microbubbles could be obtained. The

A simple procedure for the colorimetric determination of niobium in niobium-bearing steels has been developed which involves only two separations: a perchloric acid hydrolytic precipitation and a chloroform extraction of the metal derivative of 8-quinolinol. The great built of the steel components is removed as soluble perchlorates in the first separation. Elements that may contaminate the niobic acid precipitate do not interfere because they do not react with 8-quinolinol, their oxinates (quinolinates) are insoluble in chloroform, or they are not extracted by chloroform from the ammoniacal citrate solution. The method makes use of the yellow color of chloroform solutions of niobium oxinate which shows maximum absorbance at 385 mg.The method has been applied successfully to a niobiumbearing steel standard and to a series of composite steels. It involves a considerable saving in time and fewer mechanical operations without a sacrifice in accuracy.THE hitherto little known element, niobium, is no longer a laboratory curiosity but is an important element of metallurgy because of its role in preventing intergranular corrosion in stainless steels used at high temperatures.Niobium is usually found along wdth tantalum, and their accurate separation by conventional wet methods is one of the most difficult of analytical problems. Schoeller (9) thoroughly studied the chemistry of these elements and developed the basic techniques for their separation and analysis. Modifications developed by Slavin (10) reduced the time for an analysis from about 15 to 5 days.

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