Copper Determination by Alpha-Benzoin Oxime in Copper-Molybdenum Alloy Steels H. A. KAR, The Timken Steel and Tube Company, Canton, Ohio
7 HERE
a silica crucible. Cool and weigh the precipitate. Multiply the weight by 80 and divide by the number of grams of the sample, to get the copper content of the steel.
are txvo methods in common use for separating the copper from copper-molybdenum alloy steels or from molybdenum alloy steels containing copper as an impurity. I n the first method the steel is dissolved in dilute sulfuric acid and, if vanadium is present, oxidized with potassium chlorate. Both copper and molybdenum are precipitated by hydrogen sulfide gas or sodium thiosulfate. The precipitate is filtered and ignited to oxide. The oxides are fused with potassium bisulfate and the melt is dissolved with dilute hydrochloric acid. The copper is precipitated from the slightly acid (hydrochloric) solution by 5 per cent sodium hydroxide. The paper holding the copper hydroxide is fumed with sulfuric and nitric acids and the solution filtered. The filtrate is again saturated with hydrogen sulfide gas, filtered, and the residue ignited to oxide. This method is long and the work is very delicate in regard to finding a suitable condition to precipitate the copper with the exact amount of sodium hydroxide, Also, ignition of copper sulfide to oxide is not a n easy task. The second method is similar to the first one in regard to dissolving and precipitating the copper and molybdenum either by hydrogen-sulfide gas or sodium thiosulfate. The sulfides of both metals are ignited and the oxides are dissolved in dilute nitric acid. The solution is filtered and copper is separated by electrolysis. This method is also long, and complete deposition of copper by electrolysis is not sure, especially when the copper content of the steel is low. The obstacles mentioned above are removed and the time is considerably shortened b y using a-benzoin oxime for precipitating the copper.
Reactions involved in the procedure:
If steel is alloyed with tungsten, transfer 2 to 5 grams of the sample to a 600-cc. beaker, add 50 cc. of concentrated hydrochloric acid, and heat until action is complete. Add 5 cc. of nitric acid and evaporate to dryness. Cool. Add 25 cc. of hydrochloric acid and heat to dissolve the iron chromium etc. Add a few crystals of potassium rhlorate, and continue heating until tungstic oxide is completely separated. Add 150 cc. of water, heat to boiling, and allow precipitate to settle. Filter and wash with cold 5 per cent hydrochloric acid about 10 times. Add 10 to 25 grams of citric acid and render the solution alkaline by ammonia. Acidify the solution with hydrochloric acid and add 2 cc. excess for each 100 cc. of solution. Heat to boiling and saturate with hydrogen sulfide gas. Filter and proceed in the same way as described above. Experiinents proved that the most suitable medium for the precipitation of copper b y a-benzoin oxime was ammoniacal solution. Molybdenum, which can be quantitatively precipitated in acid solution, yields no precipitate in ammoniacal solution. This method functions on all grades of steel where molybdenum and copper are present, either as impurities or as alloying elements. The accuracy has been checked against a complete range of U. S. Bureau of Standards steel samples (Table I). By means of the method described above accurate copper analysis can be made in 1 hour, vhereas the former methods required from 3 to 6 hours.
Procedure Transfer 2 to 5 grams of the sample, depending on the copper content of the steel, to a 600-cc. beaker. Add 50 to 100 cc. of 10 per cent sulfuric acid and heat until action is complete. If vanadium is absent, dilute the solution to 250 cc. with hot distilled water and heat to boiling. Add 1 gram of sodium thiosulfate for each gram of steel, dissolved in 10 to 50 cc. of water. Boil the solution 10 to 15 minutes and allow recipitate to settle. If vanadium is present, add a few crystals orpotassium chlorate to the sulfuric acid solution, and heat to dissolve the insoluble. Dilute t o 400 cc. with hot water. Saturate with hydrogen sulfide gas for 15 minutes, and allow precipitate to settle. Filter on a close paper, using slow suction, and wash the paper and the beaker a few times with hot 1 per cent sulfuric acid. Transfer the paper to a silica crucible and ignite a t dull red heat. Cool the crucible, add 10 cc. of hydrochloric acid, and heat to dissolve the residue. Transfer the solution to a 400-cc. beaker, add 2 t o 3 drops of nitric acid, and treat with excess of ammonia. Heat to boiling and filter into a 600-cc. beaker. Wash with hot ammoniacal water and discard the aper. Dilute the fiitrate to 250 cc wit1 water and heat to boiling. Add 10 to 15 cc. of a 2 per cent alcoholic solution of a-benzoin oxime slowly and while stirring constantly. Boil for 1 minute. Add some ashless pulp and filter on a rapid paper. Wash 5 or 6 times vvith hot 3 per cent ammonia water, and ignite the paper in NEW LINESDISCOVERED IN COPPSRSPECTRUM.Thirty new lines in the arc spectrum of copper have been discovered by C. C. Kiess of the National Bureau of Standards, using infra-red sensitive photographic plates. All of these lines, except one, are accounted for as combinations between terms derived from an analysis of the previously known spectrum. One of the major duties of the bureau’s spectroscopy laboratory, it is pointed out, is to furnish as complete descriptions of the
TABLE I. CHECEANALYSES Average Cu Reported
Standard Samplee 2oc
%
%
0.255
0.263 0.106 0.13 0.120 0.27 0.07 0.04 0.062 0.16 0.136
0.099
300 32b 33b 35a 72 73 101 106 111
Reaults by Method
0.117 0.114 0.287 0.064 0.033 0.055 0.142 0.122
Feigl (1) has reported on the use of a-benzoin oxime for copper determination in other materials.
Literature Cited (1) Feigl,
F.,Ber., 56, 2083 (1923).
RECEIVED February 1, 1936.
spectra of the chemical elements as modern observational methods will permit. These serve as reference standards for other workers in this field. For the element copper, radiometric observations made elsewhere several years ago failed to reveal any lines in its arc spectrum in the range from 8100 to 12,000 A. The new types of photographic plates that are sensitive to infra-red light now show this region to contain many lines of great importancp in working out the atomic structure, it was stated. 193
