118
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 15, No. 2
Recommended Procedure TREATMEKT OF SAMPLE. Prepare a solution of the sample by appropriate means to contain 0.01 to 0.5 mg. of copper (see S for cop er ores and mattes). IP necessary to remove any metals precipitated by ammonia, make the solution just basic to litmus by adding 15 N ammonium hydroxide, filter into a conical flask, and wash the precipitate with 3 N ammonium hydroxide until the washings emerge colorless. Remove the flask, wash the precipitate into the original container, and dissolve the material with a minimum amount of concentrated sulfuric acid. Then repeat the precipitation and washing with ammonium h droxide as before, and catch the filtrate in the same conicar flask. Evaporate the solution to 15 ml. MEASUREMENT OF DESIREDCONSTITUENT.Xeutraliae the solution to litmus with 6 N hydrochloric acid or ammonium hydroxide and add the following in order: 2 ml. of 6 N ammonium hydroxide, 10 ml. of 0.1 per cent 1,lO-phenanthroline solution, 1ml. of 10 per cent hydroxylamine hydrochloride solution, and 20 ml. of methyl Carbitol. Dilute to 50 ml. with water, mix well and measure or compare the color by any of the usual means. A blue filter such as Corning No. 556 is recommended for filter photometers.
Summary
IC
Wavdength, m p
been completed, copper is present as the ammonia complex and, if the concentration is high enough to give a measurable color, no advantage over the ammonia method (3) can be gained b y using 1,lO-phenanthroline. If the concentration is too low, however, the proposed method may be used with good results for concentrations greater than 0.1 p. p. m. In using the method for copper ores, results were calculated b y the following procedure. Instead of comparing the transmittancy of the unknown solution with a standard, the change in transmittancy produced by adding a known amount of copper to the unknown was determined. The unknown concentration, x, was then calculated according to Beer's law expressed as follows:
The intense, brown color of cuprous-phenanthroline complex may be used as the basis of a colorimetric method for the determination of copper. Beer's law is valid for concentrations from 0.5 t o 10 p. p. m. of copper, a t least, this being the range most suitable for measurements with a 1-cm. transmission cell. The colored system is stable for at least 24 hours. Of the metals whose compounds are soluble under the conditions used, only cadmium, cobalt, nickel, and zinc interfere seriously. Metals which precipitate with ammonia are removed during the course of the procedure. Among the anions studied, only cyanide, dichromate, and thiosulfate interfere appreciably.
Literature Cited Mellon, IND.ENG.CHEM.,ANAL.En., 10, 60 (1938). (2) Foster, Langstroth, and McRae, Proc. Roy. SOC.(London), A153, (1) Fortune and
141 (1935). (3) Mehlig, IND.ENG.CHEM.,ANAL.ED., 7, 387 (1935); 13, 633
(1941). (4) Moss and Mellon, Ibid., 14, 862, 931 (1942). ( 5 ) Tartarini, Gazz. chim. ital., 63,597 (1933). ABBTBACTED from a thesis presented by M. L. Moss t o the Graduate School of Purdue University in partial fulfillment of the requirements for the degree of doctor of philosophy, May, 1942.
Modification of Calibration Apparatus x = a log T , Ta + z 1% in which T, is the transmittancy of an aliquot of the sample and !Z'a + z the transmittancy of a similar aliquot containing a small additional quantity of copper, a. Uncertainties arising from the presence of other constituents, turbidity, extraneous color, or other sources, except presence of copper in the reagents, are thus compensated. Foster, Langstroth, and McRae have a p plied this principle successfully to the spectrographic determination of lead ( 2 ) . 1,lO-Phenanthroline is somewhat less sensitive as a copper reagent than is sodium diethyldithiocarbamate. The latter reagent forms an insoluble copper salt requiring use of gum arabic or extraction with a suitable solvent. Methyl Carbitol is not satisfactory for preventing precipitation with the diethyldithiocarbamate method nor can gum arabic be used with t h e phenanthroline method.
WILLIAM R. THOMPSON Division of Laboratories and Research, State Department of Health, Albany, N. Y.
S
EVERAL minor improvements in precision calibration apparatus (1) have been introduced, and the stopcockcontrol chamber has been redesigned. Stopcock E is eliminated, as is clamp H , and instead stopcocks are added just above A and B. These and D are used to control flow rates, and the inner set, A , B, C, and F , are used as open or shut gates, as in previous procedure. Control is made easier and elimination of entrapped air after greasing a stopcock may now be accomplished without tilting the apparatus. Furthermore, a vessel of smaller capacity but otherwise the same pattern as vessel W of Figure 3 is preferable for calibration of microburets.
Literature Cited (1) Thompson, W.
R., IND.ENQ.CHEY., ANAL.ED.,14, 268 (1942).
