Rapid Qualitative Detection of Mercury in Organic Compounds IRWINSTONE,652 West 189th St., New York, N. Y.
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LTHOUGH this test is especially applicable to organic mercury compounds, because these compounds, in general, do not exhibit the characteristic reactions of ionic inorganic mercury, it may be used also to detect inorganic mercury. It uses the sensitive cuprous iodide reagent suggested by Artman ( I ) in a simple volatilization tube. A Pyrex test tube with a slotted one-hole cork is used. A glass rod passes through the cork and extends into the tube. The end of the glass rod, which is coated with the reagent, is placed about 15 mm. above the surface of the sodium carbonate mixture.
Too prolonged heating of the fusion mixture is unnecessary and is to be avoided, as tlie application of a high temperature decomposes the reagent. Arsenic and antimony do not interfere. Organic substances containing nitrogen, which give off ammoniacal or other alkaline vapors on decomposition with sodium carbonate, interfere with the test by reacting with the reagent. However, this can be circumvented by carefully placing R 2-mm. layer of potassium pyrosulfate over the alkaline fusion mixture. This will absorb the alkaline vapors during heating and not affect the sensitivity of the test. Compounds containing sulfur in certain linkages also interfere by generating sulfide vapors which change the color of the reagent to black. This interference can be prevented without loss in sensitivity by carefully placing a 2-mm. layer of lead oxide (litharge) over the sodium carbonate rrixture. Reliable and rapid results were obtained by the use of this test on a host of mercury compounds. It was also successfully applied to the detection of mercury in soaps, antiseptics, and ointments. I n these cases it was necessary to use a sample that would give about 1 to 2 mg. of mercury and increase the amount of sodium carbonate used. The test as described is not recommended for toxicological detection of mercury because of the large Fize of sample necessary and the difficulty of completely absorbing the large volume of ammoniacal vapors developed on heating the protein material.
PREPARATION OF CUPROUS IODIDE REAGENT The reagent is an aqueous suspension of cuprous iodide, prepared by mixing finely powdered cuprous iodide with about an equal weight of distilIed water. If the cuprous iodide is not a t hand, it may be conveniently prepared by the following procedure from common laboratory chemicals: Solution 1. Copper sulfate, 5 grams; water, 75 cc. Solution 2. Sodium sulfite, 5 grams; potassium iodide, 11 grams; water, 75 cc. Dissolve solutions 1 and 2 separately, then mix and allow precipitate t o settle. Filter or centrifuge and wash with water. PROCEDURE Mix about 5 to 10 mg. of the organic compound to be tested with about 0.'5 gram of anhydrous sodium carbonate and place in a dry test tube. Dip the glass rod to a depth of 4 to 5 mm. into the cuprous iodide suspension, remove, and allow to dry partially. PIace the coated rod in the test tube. Hold the tube at a 45" angle and heat the lower end gently with a small flame. In the presence of mercury, the reagent quickly turns from white to a salmon color or pink. The reaction is very sensitive, the limit using this procedure being about 0.02 mg. of mercury.
LITIZRATURE CITED (1) Artman, Po,2. a d .Chem., 60, 81 (1921). R E C E I V ~February D 15, 1933.
Nickel Tubes in Organic Combustions FRANCIS EARLRAY,University of Cincinnati, Cincinnati, Ohio
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N A RECENT article Couch (8) reports an interesting method for the analysis of difficultly combustible organic compounds. The author encountered similar,difficulties in the combustion of nitro compounds of high molecular weight. The material would volatilize and condense as a tar on the glass tube and could not be properly burned. When nickel tubes (furnished through the courtesy of C. 5. Bianowicz of the International Nickel Company) were substituted for glass, the material could be burned completely. Certain nitro and nitroso compounds, however, gave high values for nitrogen when burned in a metal tube and nitric oxide was found in the nitrometer unless the combustion was carried out with tedious slowness. Evidently the reduced copper spiral was not very effective, possibly because of the completely oxidized interior of the tube. This difficulty was surmounted by mixing the sample in a porcelain boat with copper powder (Karlbaum's Natur-Kupfer). The results obtained by this method were very satisfactory. In using a nickel tube, 12-inch (30-cm.) lengths of 0.125-inch (0.3-cm.) copper tubing were Wound around the combustion tube a t each end and a stream of water was passed through these coils to prevent the rubber stoppers f;om melting. A
nickel tube open a t both ends was used. Carbon dioxide was generated in a small Kipp from marble chips previously boiled with slightly acidulated water, If the closed-end Dumas tube is preferred, one end of the nickel tube may be threaded and a threaded nickel cap screwed firmly in place. Nickel tubes have also given excellent service in carbonhydrogen combustions. A nickel tube is good for a t least one hundred combustions for carbon and hydrogen or a much greater number of nitrogen determinations. The combustions may be carried out rapidly as the tubes may be cooled between heatings with a blast of air. The tubes are not, of course, brittle, which is the objection to silica tubes, nor do they oxidize rapidly and quickly deteriorate as do copper tubes (1, 3). LITERATURE CITED (1) Avery, S., and Hayman, D., IND. ENG.C H E M .Anal. , Ed., 2, 336. (1930). ( 2 ) Couch, J. F., J , Am. Chern, sot., 55, 852 (1933), (3) Evans, R. N., ISD. ENG.CHEW,Anal. Ed., 5, 61 (1933).
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