Determination of Ruthenium by Thionalide J
Absorption of Ruthenium Tetroxide with Hydrogen Peroxide W. J. ROGERS, F. E. BEARIISH, m
D D. S. RUSSELL University of Toronto, Toronto, Ontario, Canada
Ruthenium tetroxide is distilled from a dilute sulfuric acid solution containing sodium bromate and absorbed in a 3 per cent solution of c. P. hydrogen peroxide. Ruthenium is recovered by precipitation with thioglycolic 8-aminonaphthalide; the complex is ignited in air, reduced in hydrogen, and weighed as ruthenium metal.
T
HE separation of ruthenium when present with other
metals is practically always accomplished by oxidation to the volatile tetroxide by means of chlorine, perchloric acid, or sodium bromate. Various procedures have been suggested for the subsequent determination of ruthenium in the resulting distillate. Howe and Mercer (3) absorbed the liberated ruthenium tetroxide in a dilute solution of potassium hydroxide, containing some alcohol, and precipitated ruthenium as an oxide by warming on a steam bath; however, they could not satisfactorily free this precipitate from alkali. Gilchrist (2) adopted and improved a method proposed by Ruff and Bornemann ( 7 ) for the determination of osmium, in which hydrated osmium dioxide was recovered from alkaline osmate solutions by neutralizing with sulfuric acid. Gilchrist avoided error due to the occlusion of silica or the absorption of alkali by approaching the neutralization of the ruthenium solutions from the acid side. He neutralized the acid solution with a 10 per cent sodium bicarbonate solution to pH 6 , and precipitated the ruthenium as a hydrated oxide. This hydrated oxide was washed with ammonium sulfate solutions to avoid deflagration and the reduced ruthenium was leached with hot water t o remove soluble salts. Because no other more satisfactory method for the determination of ruthenium was available, this hydrolytic procedure has been used in this laboratory for many hundreds of determinations of microsamples. The conclusion reached by the authors as a result of this experience is that consistently accurate results are not obtained with small samples. It would seem that a large proportion of the absolute error associated with the macrodetermination also applies to the microdetermination. The inaccuracies appear to be due in part to the inefficiency of the final leaching process. For the purposes of semimicrowork at least this method was not considered reliable. Berg and Roebling (1) studied the reaction of "thionalid" (thioglycolic P-aminonaphthalide), with base metals, and stated that the reagent precipitated platinum and palladium. Kienitz and Rombock (4) determined rhodium by addition of thionalide and titration of excess reagent. The efficiency of this organic compound for the precipitation of the platinum metals is being examined in the authors' laboratories, and the following is a report of its successful application to the determination of ruthenium.
distilled, constant-boiling hydrochloric acid (21 per cent by weight). The absorbing solutions were refluxed in a cold finger reflux condenser t o ensure total conversion to chlororuthenic acid. The solution was concentrated, and ammonium chlororuthenate was precipitated by the addition of a saturated solution of ammonium chloride. The crystals were filtered through an A2 filtering crucible, washed with 95 per cent alcohol, redissolved in hot 2.3 N hydrochloric acid, and filtered hot. The filtrate was concentrated and cooled rapidly. The resulting crystals were filtered, washed with 95 per cent alcohol until the washings were colorless, then desiccated over phosphorus pentoxide, and ground in an agate mortar. Analysis of salt KO.1by direct ignition in hydrogen yielded 30.73 per cent ruthenium metal. Sample 2 was similarly analyzed, and yielded 30.90 per cent ruthenium metal. A standard solution was prepared from No. 2 by dissolving a weighed amount in 0.5 N hydrochloric acid solution. The calculated ruthenium content was 10.03 mg. per 10.00 ml. of solution.
Precipitation of Ruthenium with Thioglycolic P-Aminonaphthalide DETERMIK.4TION OF ORGANIC CONSTITUENT-RUTHENIUM RATIO. The precipitation of the ruthenium-organic compound was made from a solution of ruthenium chloride in 95 per cent ethyl alcohol. The resulting preci itate was filtered through a filtering crucible, washed with ethyPalcoho1 in which the precipitant is soluble, dried at 110" C., and weighed. It was then moistened with water and covered with a wet ashless filter-paper pulp, ignited, and reduced in hydrogen. In two typical cases the weight of sample was 29.07 and 20.81 mg. The weight of ruthenium metal recovered was 5.42 and 3.82 mg. These indicate a ratio of one atomic weight of ruthenium t o two formula weights of thionalide. Weighed samples of ammonium chlororuthenate were dissolved in an acidified aqueous solution, diluted, and brought almost to a boil. An excess of the calculated amount of organic precipitant
TABLE I. DETERMINATION OF RUTHENIUM WITH THIOQLYCOLIC P-AMINONAPHTHALIDE No. 1 2 3 4 5 6
7 8 9 10 11 12 13 14 15 16 17 18 19 20a 21 22 23"
24 250 26
Preparation of Ammonium Chlororuthenate Ammonium chlororuthenate was prepared by distillation from a solution of ruthenium chloride, sulfuric acid, and sodium bromate. The evolved ruthenium tetroxide was absorbed in re-
0
561
Volume of Concd. Acid MI. 0.4 HCI 0.4 HC1 0.4 HC1 0.4 HC1 0.4 HC1 0.4 HC1 0.15 HC1 0.1 HCI 0.25 HC1 0.25 HC1 0.3 HCI 0.5 "Os 0.5 HNOi 0.5 HNOs 0.5 HNO: 0.5 HNO: 0.6 HNOs 0.5 HC1 0.5 HCl 0.5 HC1
HC1 HC1 HC1 HC1 5 . 0 HC1 0.15 HC1
Total Weight of Weight Weight Volume (NHdz- of Ru of Ru Absolute Taken Recovered Error of Soh. RuCls MQ. M1. MQ. MQ. Mu. 20.89 6.42 6.44 60 4-0.02 60 21.38 6.57 6.56 -0.01 3.29 60 10.68 3.32 4-0.03 17.88 5.49 5.53 60 4-0.04 18.58 5.73 5.71 75 4-0.02 21.21 60 6.52 6.55 I-0.03 150 48.18 14.81 14.85 +0.04 50 10.03 10.02 -0.01 50 10.03 10.09 I-0.06 10.03 10.03 50 0.0 50 10.03 9.99 -0.04 60 21.49 6.60 6.13 -0.47 60 9.03 29.40 8.97 -0.06 150 26.77 8.23 7.96 -0.27 150 46.01 14.13 13.87 -0.26 150 39.40 12.11 11.70 -0.41 175 48.62 14.94 14.49 -0.45 200 6.78 6.84 -0.06 6.84 6.87 200 +0.03 200 ... 6.87 6.84 4-0.03 6.86 6.84 200 +0.02 200 -0.04 6.80 6.84 200 4-0.01 6.85 6.84 200 -0.15 6.69 6.84 6.66 200 6.84 -0.18 27.47 60 8.44 8.83 -0.11
... ... ... ...
1.0 1.0 2.0 5.0
... ... .. . ... ...
]
0.15 HNOs Nos. 20. 23, and 25 each contained 6 grams of sodium chloride.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
was weighed out, dissolved in 3 ml. of alcohol, and added to the solution by means of a glass capillary. The liquid was boiled until the precipitate was coagulated, filtered through a 7-cm. Whatman No. 42 paper, and washed thoroughly with hot water. The paper and precipitate were transferred t o a porcelain crucible and charred, and the carbon was burned off. The ignition period was then extended for only 2 minutes. The residue was reduced in hydrogen, cooled in hydrogen, and weighed as metallic ruthenium. There was no loss by decrepitation or deflagration during the ignition. Results are recorded in Table I. The effects on the efficiency of the recovery of varying concentrations of hydrochloric acid, of the presence of nitric acid, and of the presence of sodium chloride were investigated. The results are recorded in Table I. The authors were not successful in discovering a direct test for ruthenium in the presence of thioglycolic p-aminonaphthalide; however, the filtrates were examined four at a time by evaporating nearly to dryness, treating with 20 ml. of sulfuric acid, and transferring to the distillation flask. Organic matter was then destroyed by additions of nitric acid; sodium bromate was added and the solution distilled into 1 t o 1 hydrochloric acid solution saturated with sulfur dioxide. The total absorbing solutions were combined and evaporated to a volume of about 0.2 ml., and the thiourea test was applied. In all cases not more than a faint trace of ruthenium was found. Table I shows that quantitative results are obtained when the precipitation is carried out in about 0.2 to 0.5 N hydrochloric acid solution. In alkaline solution it was found that the ruthenium-organic complex did not coagulate properly on boiling. Nos. 24 and 25, Table I, indicate the effect of too much acid. The precipitation when carried out in nitric acid solution yields consistently low results. The presence of sodium chloride in small amounts does not. interfere with the precipitation.
Absorption of Ruthenium Tetroxide Gilchrist (9) recommended the absorption of ruthenium tetroxide in 1 to 1 hydrochloric acid solution freshly saturated with sulfur dioxide. While this reagent is undoubtedly an efficient absorbent for ruthenium tetroxide, the subsequent determination requires evaporation to an acid sirup, removal of sulfur dioxide by digestion with concentrated hydrochloric acid, and final filtration to remove solids. This procedure is lengthy and there is considerable difficulty and uncertainty associated with the complete removal of sulfur dioxide. Practically all the attempts made in this laboratory to determine quantitatively small amounts of ruthenium in the distillate by either the hydrolytic or the new method recommended in this report resulted in failure to secure concordant results. Attempts were made to absorb ruthenium tetroxide in icecold water and ice-cold dilute hydrochloric acid solutions. Although the volumes of the absorbents were increased considerably, the collection of the tetroxide was in no case found to be complete. With the hydrochloric acid a brown ruthenium compound collected on the walls and tubes of the receivers. A considerable loss of ruthenium occurred on warming both acid and water absorbents to room temperature. These facts confirm the statements made by Ransohoff and Gutbier (6) and others. Krauss and Schrader (6) prepared pure ruthenium dioxide by distilling ruthenium tetroxide into a 4 per cent solution of hydrogen peroxide and warming the distillate on a steam bath.
It was decided to investigate the efficiency of hydrogen peroxide as an absorbent for ruthenium tetroxide. The apparatus used throughout this work was a standard distillation equipment (sold by the Scientific Glass Apparatus Co., Bloomfield, N. J.; catalog No. 51306, without condenser).
VOL. 12, NO. 9
Measured samples of the standard ammonium chlororutheoate solution were transferred to the distillation flask, and diluted to a volume of approximately 200 ml., and 10 ml. of sulfuric acid were added. Then 35 ml. of a 3 per cent aqueous solution of c. P. hydrogen peroxide were placed in the first absorption flask and 15 ml. in the second. The receivers were cooled by means of an ice bath. To the distillation flask 25 ml. of sodium bromate were added and the ruthenium tetroxide was removed by gentle boiling. It was observed that the solutions in the first receiver became greenish-brown, Jyhile the solutions in the second receiver were sometimes colored bromine-yellow. The third receiver contained sulfur dioxide-hydrochloric acid to test for the completeness of absorption. In all cases this concentrated absorbent was treated with thiourea and ruthenium found absent. Two hours' boiling was sufficient to remove the tetroxide completely. This was proved by further distillation into 1 to 1 hydrochloric acid saturated with sulfur dioxide, concentrating the solution, and testing with thiourea. The total hydrogen peroxide absorbent was washed into a beaker to a volume of approximately 150 ml., about 0.6 ml. of hydrochloric acid was added, and the solution was boiled until evolution of gas ceased. Thioglycolic paminonaphthalide was added as described above. Results obtained by this method are recorded in Table 11. The ruthenium-organic complex does not coagulate well if the hydrogen peroxide contains acetanilide as a stabilizer, and low results are aln-ays obtained. The distillate must be heated to boiling before the addition of thioglycolic P-aminonaphthalide. If this is not done the hydrogen peroxide reacts with the precipitant. The product of this reaction mas isolated, and proved to be a white material, the melting range of which was 178' to 183". S o attempt was made to purify this product. The effects of cooling the absorbing solutions in a water bath, of absorbing a t room temperatures, and of distilling from nitric acid-sodium bromate solutions mere investigated. Some of the results are recorded in Table 11. The important advantage offered by absorption with hydrogen peroxide as compared to absorption with the sulfur dioxide-hydrochloric acid reagent is that the precipitation of the ruthenium-thionalide can be made directly on the distillate; no interfering substance is present, and no evaporation is required. During these investigations the efficiency of several absorbing media was investigated. The following is a brief resume of the experiments. 1. Ruthenium tetroxide was absorbed in a 10 per cent solution of sodium hydroxide. The absorbing solution was strongly acidified with hydrochloric acid, taken to a small volume on the steam bath, and filtered through a 5.5-crn. Munktell No. 00 paper to remove any trace of silica. The solution was then brought to pH 4. The acidity was adjusted to a normality of 0.2 and thioglycolic 8-aminonaphthalide was added. In the case of two typical samples 33.41 and 36.95 mg. of salt were taken; the cor-
T.4BLE
Method RutheRutheVolume of of Cooling nium nium Re- Absolute Acid Added Absorbent Taken covered Error M1. MQ. M Q. MQ. 26 0 . 6 HC1 Ice 10.03 9.99 -0.04 10.06 +0.03 27 0.6 HC1 Ice 10.03 10.05 +0.02 28 0 . 6 HCl Ice 10.03 9.99 -0.04 29 0 . 6 HC1 Ice 10 03 10 03 0.0 30 0 . 6 HC1 Ice 10 03 Ice 10.03 10.12 +0.09 31 0.6HC1 8.93 -1.10 Water 10.03 32 0 . 6 HC1 -0.13 10.03 9.90 Water 33 0 . 6 HC1 9.93 -0.10 Water 10.03 34 0 . 6 HC1 10.03 9.74 -0.29 35 0 . 6 HC1 Water 9.35 -0.68 36" 0 . 2 HC1 Ice 10.03 9.99 -0.04 37 0 . 2 HC1 Ice 10.03 9.13 -0.90 38 0 . 6 HKOa Ice 10.03 9.76 -0.27 39 0 . 6 HXOa Ice 10.03 A black oxide pre40 0 6 HC1 Air 10.03 Air 10.03 cipitated out in 41 0 . 6 HC1 Air 10.03 absorbent 42 0 . 6 HCI Nos. 36 t o 39 were distilled from nitric acid-sodium bromate solution So.
a
11. DETERMINATION OF RGTHENIUM
SEPTEMBER 15, 1940
ANALYTICAL EDITION
responding weights of ruthenium were 10.27 and 11.35 mg. The weights of ruthenium metal recovered were 10.18 and 11.41 mg. This method, however, proved to be tedious. 2. Ruthenium tetroxide was distilled into a hot acidified solution of thioglycolic p-aminonaphthalide. The rutheniumorganic complex precipitated immediately, but because of mechanical difficulties the method is not recommended. 3. An acidified 10 per cent solution of potassium iodide was used as an absorbing solution. Too much difficulty was encountered in removing iodine from the ruthenium triiodide.
563
recovered directly from this solution by precipitation with the thioglycolic 0-aminonaphthalide. The hydrogen peroxide, however, must be free from acetanilide. An aqueous solution of sodium hydroxide may be used as an absorbent and the ruthenium recovered quantitatively, but the procedure is lengthy.
Literature Cited
Summary
(1) B e r g , R., a n d Roebling, W., Angew. Chem., 47, 404 (1934). (2) Gilchrist, R . , Bur. Standards J . Research, 3, 993 (1929); 12, 283
Ruthenium can be quantitatively precipitated from a 0.2 to 0.5 N hydrochloric acid solution by means of thioglycolic 0-aminonaphthalide. A cold 3 per cent solution of hydrogen peroxide quantitatively absorbs ruthenium tetroxide, and the ruthenium can be
(1934). (3) Howe, J. L., a n d M e r c e r , F. N., J . Am. Chem. Soc., 47, 2927 (1925). (4) Kienitz and R o m b o c k , 2.anal. Chem., 117, 241 (1939). ( 5 ) Krauss, F., a n d S c h r a d e r , G., 2. anorg. Chem., 176, 385 (1928). (6) Ransohoff, F., and G u t b i e r , A., Ihid., 45, 243 (1905). (7) Ruff, O., and B o r n e m a n n , F., Ihid., 65, 429 (1910).
Apparatus for Semimicrodetermination of Carbon and Hydrogen CARL NIEMANN AND VANCE DANFORD California Institute of Technology, Pasadena, Calif.
T T IS the purpose of this communication to describe, in condktail, the construction and operation of a n
1 siderable
apparatus specifically designed for the semimicrodetermination of carbon and hydrogen in all types of organic compounds.
Furnace Assembly COMBUSTION-ZONE FURNACE. A piece of 0.625-inch (1.59cm.) copper rod, 0.875 inch (2.22 cm.) long was turned down to a diameter of 0.375 inch (0.95 cm.) for a distance of 0.125 inch (0.32 cm.) from one end and the cylinder of lesser diameter was threaded. A seamless nickel tube, 0.531 inch (1.35 cm.) in inside diameter, 0.688 inch (1.75 cm.) in outside diameter, and 10.25 inches (25.65 cm.) long was drilled and tapped at its mid-point, the copper rod was screwed into the opening, and the nickel tube was reamed out, so as t o remove the portion of the copper rod protruding into the interior of the tube. A 0.438-inch (1.11-cm.) hole was drilled axially into the copper rod to a depth of 0.25 inch (0.64 cm.). From the bottom of this hole, a 0.25-inch (0.64-cm.) hole was drilled to a depth of 0.75 inch (1.91 cm.), measured from the top face of the rod, or to the projected external circumference of the nickel tube. The tuhular part of the assembly was sheathed with a double layer of mica and a single layer of 0.063-inch (0.16-cm.) asbestos cord, the latter bring wound to within 0.25 inch (0.64 cm.) of each end of the nickel tube. (In this operation a sheet of first-grade mica, free of flaws, is split along the cleavage plane until the thickness of the sheet is reduced to the point of necessary flexibility.) Using the asbestos cord as a spacer, the sheathed nickel tube was wound with 158 inches (401.32 cm.) of No. 28 Chromel A resistance wire. I n this operation sufficient wire was taken, 278 inches (706.12 cm.), to leave 48 inches (121.93 cm.) unwound a t each end. I n winding the section of the tube bearing the copper well it was found convenient to place a square-sided U-shaped piece of wire, covered with porcelain tubing, around the well with the open end of the U facing one end of the nickel tube. The wire in this region was wound back and forth over the porcelain arms. When the windings were in place the U was closed by inserting a second U, with short exposed wire arms, into the free ends of the porcelain tubes of the first U. The assembly was covered with a second layer of 0.063-inch (0.16-cm.) asbestoscord and the 48inches (121.92 cm.) of wire remaining a t each end were wound in the interstices of the second layer of asbestos cord for a distance of 1.25 inches (3.18 cm.) from each end. After securing the ends of the winding with asbestos cord, the wires were brought to the center of the tube in a single turn and anchored to each other by means of a small double-hole porcelain insulator. From here to their point of exit from the body of the furnace, the wires
were insulated with short lengths of small-diameter porcclain tubing. Two end plates, one 4 X 4 inches (10.16 X 10.16 cm.), the other 4 X 5 inches (10.16 X 12.7 cm.), werc cut from 0.5-inch (1.27-cm.) Transite board and in the center of the square plate a 0.531-inch (1.35-cm.) hole was drilled. This hole was countersunk so as to produce a shoulder 0.281 inch (0.71 cm.) deep and a diametcr equal to that of the nickel tube and all its windings. Four 0.219-inch (0.56 cm.) holes were drilled at a point on the diagonals 0.5 inch (1.27 cm.) in from the corners of the square and were countersunk on both sides to a depth of 0.125 inch (0.32 cm.) and a diameter sufficient to accommodate a standard 0.188inch (0.48-cm.) brass hexagonal nut. A circular groove 3.5 inches (8.89 cm.) in diameter, 0.063 inch (0.16 cm.) wide, and 0.25 inch (0.64 cm.) deep was cut on the side of the plate bearing the countersunk portion of the central orifice. The rectangular plate was divided into a 4 X 4 inch (10.16 X 10.16 cm.) square and a 1 X 4 inch (2.54 X 10.16 cm.) rectangle and the square portion was machined exactly as described for the square plate. Two metal binding posts were centrally located on the inside face of the 1 X 4 inch (2.54 X 10.16 cm.) rectangle and by means of 0.063-inch (0.16-cm.) holes, drilled in the end plate, the leads of Chromel wire were brought out of the interior of the furnace and secured to the binding posts. A cylinder 3.5 inches (8.89 em.) in diameter and 10.25 inches (26.04 cm.) long, with a 0.438-inch (1.11-cm.) hole at the mid-point, was formed from a sheet of 26-gage stainless steel and the lap joints were secured by rivets. With the aid of four 0.188-inch (0.48-cm.) brass tie rods, 10.75 inches (27.31 cm.) long and with 10-32 threads on both ends, the furnace was assembled and the space betwecn the nickel tube and the stainless steel tube was filled with asbestos pulp. During this operation access to the copper thermocouple well was secured by inserting a glass tube through the 0.438-inch (1.11-cm.) hole in the steel jacket and in the 0.438-inch (1.11-cm.) hole of the copper well. The glass tube was cut off flush with the exterior surface of the jacket and was kept in place, in the copper well, with an asbestos gasket. In the assembly four legs constructed from a 0.125 X 1 inch (0.32 X 2.54 cm.) hot-rolled iron bar were attached to the inside of the end plates with nuts held on brass tie rods. These legs xere 7 inches (17.78 cm.) high, were bent a t right angles to form a foot 1.5 inches (3.81 cm.) long and, at the top, were cut away so as not to interfere with the steel jacket. Each foot was drilled and tapped in its central portion for a 6-32 thread. LEADPEROXIDE-ZONE FURNACE. A shoulder 0.25 inch (0.64 cm.) wide and 0.375 inch (0.95 cm.) deep was cut on each end of a 2-inch (5.08-cm.) copper rod 3.5 inches (8.89 cm.) long. After drilling a 0.688-inch (1.75-cm.) hole axially through the cylinder, H second hole, 0.375 inch (0.95 cm.) in diameter, was drilled ra-
