ANALYTICAL EDITION
March, 1945
Determination of Copper in Aluminum
Alloys
SIDNEY WEINBERG Industrial Test Laboratory, U. S. Navy Yard, Philadelphia, Pa.
DIRECT acid solution procedure for the determination of copper in aluminum alloys by electrodeposition gives excellent results. The method employs a mixture of perchloric acid and nitric acid to effect solution of the alloy. This procedure is particularly suitable for continuous analyses in which the presence of salts introduced by caustic solution methods followed by acidification (1, 2 ) is objectionable, and for certain types of alloys, such as high-silicon alloys, for complete solution of the sample proceeds readily. Chromium] manganese, and nickel can be determined after electrolysis. The determination of chromium can be very readily accomplished on a separate sample by oxidation with perchloric acid. Manganese can also be estimated, after solution of the alloy, by the usual oxidation procedures. Nickel is best determined on the electrolyte by gravimetric or colorimetric methods using dimethylglyoxime reagent.
Table I.
Results of Acid Solution Method N.B.S. Values 4.11
Alkali Procedure
N.B.S. 86a
7.65
..
N.B.S. 86b
7.87
..
Alcoa 52-S
..
Alcoa 2-S
..
Alcoa Alcoa Alcoa Alcoa .qlCOa
..
195 X-195 (1) X-195 (2) 355 B-195
.. .... ..
..
0.30 0.30 0.16 0.16 4.10 4.47 4.36 1.30 4.30
LITERATURE CITED
(1) Blok, N. I., Shumilova, N. A., and Gorskaya, N.F., Zavodskaya Lab., 10,28-31 (1941). (2) Sloviter, H. A., IND.ENG.CHEM.,ANAL.ED.,13, 235-6 (1941). OPINIors expressed are those of the author and should not necessarily be construed to represent the views of the Navy Department.
A
Alloy Designations N.B.S. 85
197
Acid Procedure 4.10 4.11 7.66 7.65 7.66 7.88 7.88 7.87 7.87 0.31 0.31 0.16 0.16 4.08 4.45 4.36 1.33 4.31
Results obtained are shown in Table I, compared to the alkali method. Deposits are bright and adherent. The procedure is applicable to the complete range of copper occurring in aluminum alloys. Elements which deposit in strong acid solutions interfere-for example, bismuth in screw machine products. Fortunately, they are seldom encountered. If present, a subsequent purification of the deposit is necessary.
PROCEDURE. Dissolve 1 gram of aluminum alloy drillings in a 200-ml. electrolytic beaker by adding 20 ml. of perchloric acid (70’33, 5 ml. of distilled water, and 5 ml. of concentratd nitric acid (specific gravity 1.42). Warm gently after the initial vigorous reaction decreases to complete the solution. A second 5-ml. addition of water often facilitates completion of the reaction. Add 4 ml. of concentrated nitric acid, and 2 ml. of dilute sulfuric acid (1 to 1 ) and bring to a boil to ex el nitrogen oxides. Wash down the sides of the beaker with distised water at room temperature and dilute to 150 ml. ElectroIyze for 30 to 40 minutes, using a current of air to a itate the electrolyte. A platinum wire spiral serves as the anoie and a platinum gauze cylinder 4.4 cm. (1.75 inches) in diameter and 5 cm. (2 inches) in len th as the cathode. The current is adjusted to 2 to 3 amperes a t &e beginning of the electrodeposition and need not be adjusted afterward. The completeness of the deposit can be tested by use of a sodium sulfide solution.
Packing Support for Laboratory Fractionating Columns J O H N R. L O N G The Goodyear Tire & Rubber Company, Akron, Ohio
0
N E of the more difficult problems in building a packed laboratory fractionating column is the construction of a satisfactory support for the packing. Various designs have been proposed, but all have one or more disadvantages: flooding because of insufficient capacity] corrosion of construction mateiials, or ease of breaking. These disadvantages have been eliminated in a packing support which the writer has been using for several years. This support has the additional advantage that the rate of return of the liquid to the still pot is easily observed, since the liquid flows from a single drip point. Packing supports have been constructed for columns ranging in size from 7 to 52 mm. in diameter and packed with packing ranging from 0.24-cm. (a/&nch) glass helices to 0.6-cm. (0.25inch) Berl saddles. The glass blowing involved in the construction of the packing support is of only moderate difficulty and consists of two steps.
A short piece of tubing the same diameter as the column is shrunk and pulled down in a flame to give a tube having a conical shaped closed end, the cone having the same wall thickness as the tube, A . The tip of the cone is then heated quickly with a fine pointed flame, such as that obtained with a No. 1 tip of a Hoke-Jewel torch and a small bulb is partially blown out. This procedure is repeated in such a manner that the surface of the cone is covered with uniformly spaced small bulbs, B . The partially blown out bulbs are sanded off with coarse sand paper, giving a perforated cone. These perforations should be small enough, so that the packing does not fall through, and have an area equal to the crosssectional area of the column. Some practice is required to produce small holes for small packing. The cone is A B carefully heated until all the holes have been fire-polished and then annealed. The prepared section, B , is attached to the bottom part of the column with a ring seal, C. The completed unit, C, is then sealed to the tube which is the main part of the column. The best method of making this ring seal is as follows: The parts are clamped horizontally in such a position that they touch where the seal is to be made. The portion of glass in the vicinity of the seal is kept hot during the next operation by a relatively cool gas-air &me of a blast lamp. If the flame is too hot the glass will sag. A portion of the outer tube is heated with a fine pointed flame and pushed against the inner tube with a file or iron wire. This is repeated along the entire length of the seal. The seal is worked out in the usual manner and annealed in a flame, or preferably in a furnace. c
