Photometric Determination of Copper in Aluminum and Lead-Tin Solder with Neocuproine JAMES W. FULTON and JANE HASTINGSI Transformer Laboratories Department, G e n e r a l Electric Co., Pittsfield, Mass.
treating with copper-free hydroxylamine hydrochloride solution, by neocuproine solution and subsequent extraction with chloroform. Hydrobromic acid-bromine mixture, 20 ml. of bromine added to 180 ml. of hydrobromic acid, 48%.
$lethods are described for the use of neocuproine (2,9-
dimethyl-1,lO-phenanthroline)in determining copper in aluminum and lead-tin solders. The methods are rapid and require no chemical separations except for the extraction of the copper complex, and the results compare favorably with other, more tedious, methods for determining copper. Although the procedure for determining copper in aluminum has been particularly useful for the analysis of high-purity aluminum (99.6 to 99.99% aluminum), it has been applied to high-silicon aluminum. The method is sensitive and accurate in the range of 0.002 to 1.007~of copper in aluminum. The procedure for determining copper in lead-tin solder has been applied in the range of 0.004 to 0.4% of copper. The copper-neocuproine complex has its absorbancy maximum at 434 mp. Conformity to Beer’s law is observed for both determinations. A calibration curve prepared with pure copper may be used for the calculations.
CALIBRATION CURVE
A calibration curve vias prepared by carrying through the procedure on samples containing varying amounts of the standard copper solution. The absorbancies, corrected for a blank of reagents, were plotted against the concentration of copper in milligrams per milliliter. The system obeys Beer’s law between 0.001 and 0.004 mg. of copper per ml. when measured in a 10-mm. light path cell. PROCEDURE FOR LE.4D-TIY SOLDERS
Dissolve 0.500 gram of solder in 25 ml. of 48% hydrobromic, acid. When the reaction ceases, add dropwise just enough hydrobromic acid-bromine mixture to clear the solution. Cool and dilute to 100 ml. in a volumetric flask. Transfer an aliquot containing 0.04 to 0.20 mg. of copper to a separatory funnel. Dilute to 50 ml. with water. .4dd 5 ml. of hydroxylamine hydrochloride solution (10%) and 10 ml. of sodium citrate solution. Adjust the pH of the solution to between 4 and 6 and add 10 ml. of neocuproine solution. Shake to mix thoroughly and extract by shaking with 10 ml. of chloroform for 30 seconds. Transfer the chloroform layer to a 50-ml. volumetric flask. Rinse the stem of the funnel with two 1-ml. portions of chloroform. Repeat the extraction ti-ith 8 ml. of chloroform and rinse the stem as before. Dilute to volume with ethyl alcohol and determine the absorbancy a t 454 mF. Make a correction for the absorbancy of a blank of the reagents using an ethyl alcohol-chloroform mivture (3 to 2) as a reference at 100% transmittance.
T
HE specificity of 2,9-dirnethyl-l,lO-phenanthroline(neocuproine) for cuprous copper has been described by Smith arid JIcCurdy ( 3 ) . Luke and Campbell ( 2 ) have applied the coloi ed system to the determination of copper in germanium and reported no interference from 58 metals. Gahler ( 1 ) used the redgent for determining copper in iron and steels and reported on the effect of p H and some anions on the extraction of the colored complex. The use of the reagent has been evtended in this laboratory t o the determination of copper in aluminum and lead-tin solder. Gahler’s procedure for extracting the complev with an ethyl alrohol-chlorofor m mivture was followed.
PROCEDURE FOR ALUMISUM
Transfer 0.500 gram of aluminum to a 150-ml. glass beaker and dissolve in 5 ml. of hydrochloric acid (1 to 1). Rinse the sides of the beaker n
