V O L U M E 26, NO. 4, A P R I L 1 9 5 4 water, and evaporate to fumes of sulfur trioxide. Repeat tuice to ensure complete removal of nitric acid and then cool. If the material does not contain organic matter, dissolve in hydrochloric acid or sulfuric acid. If nitric acid is required to effect solution, this then must be removed as described in the paragraph above. Tin, especially in the oxidized condition, hydrolyzes readily from a sulfuric acid medium. Hydrolysis of tin will also occur, though not so readily, from a hydrochloric acid medium, if the acid concentration becomes too low. I n the event that an aliquot of the sample is to be used for analysis, it is recommended that the entire sample be a t least 1 to 9 in hydrochloric acid, even if sulfuric acid is present. With both organic and inorganic materials, a blank should be carried through the entire procedure with the sample. Introduce 2 grams of hydrazine sulfate (powdered solid) with the aid of a minimum amount of water to the distillation apparatus [see Figure 7 in ( I ) ] . Transfer the sulfuric or hydrochloric acid solution of the sample, containing not less than 0.04 mg. and not more than 0.8 mg. of tin, to the distillation apparatus iqith the aid of not more than 20 ml. of water. Add 10 ml. of phosphoric acid, 20 ml. of hydrochloric acid and increase the sulfuric acid content to a total of 25 ml., if this amount is not already present Add 50 ml. of water to a 400-ml. beaker and place under the condenser so that the tip is submerged a t least 0.25 inch. The apparatus should be PO arranged that the distillate can be removed at any time. Place 150 ml. of hydrochloric acid in the acid bulb, start a slow stream of carbon dioxide through the solution, bring to a boil, and boil gently. When the temperature has reached 165’ C., introduce the hydrochloric acid from the bulb into the flask a t such :t rate that the temperature remains hetween 1%’ to 170” C. (about 40 drops per minute). When about 125 ml. of hydrochloric acid has been introduced into the flask. allow the distillation to continue but remove distillate, \\ash down stem of condenser, and replace the first beaker with a 100-ml beaker containing 25 nil. of water. When only approximately 1 to 2 ml. of hydrochloric acid remain in the bulb, close the stopcock to shut off the flow of hydrochloric acid, shut off the heat. lower the distillate until free of the condenser, and wash down the stem of the condenser with water. Discard both distillates. Place a 200-ml. tall-form beaker containing 40 ml. of water under the condenser so that the tip of the condenser is about 0.25 inch from the bottom of the beaker. Place 45 ml. of a mixture of hydrochloric acid (15 ml.) and hydrobromic acid (30 ml.) in the acid bulb; hen the temperature has dropped to 130” C., start the heat and begin to introduce the acid from the bulb when the temperature begins to rise Introduce the acid into the flask a t a rate of 30 to 40 drops per minute and maintain the temperature between 137” to 147’ C. When only approximately 1 ml. of the acid remains in the bulb, close the stopcock to shut off the flow of acid, shut off the heat, and lower the distillate until free of the condenser. Shut off the flow of car-
737 bon dioxide and wash down the stem of the condenser with water. Pipet 5 ml. of sulfuric acid (3 to 7 ) into the distillate, stir, place on a hot plate, and bring to a boil. Boil gently for 5 minutes and then cool to room temperature. Add 10 ml. of hydrogen peroxide (30%), stir, cover with a ribbed watch glass, and place on a hot plate. (Some brands of peroxide give a very high blank and should not be used. The authors have found Merck’s Superoxol C.P. satisfactory.) Boil the solution gently until it becomes almost colorless or until no more red fumes of bromine are given off. Remove from the hot plate, shift the cover slightly, and add 10 ml. of hydrogen peroxide (30%) in small portions, stirring and waiting for the reaction to subside before each addition. Replace on the hot plate and boil gently until the solution is colorless. Remove from the hot plate and add a t one time, an additional 5 ml. of hydrogen peroxide (30%). Replace on the hot plate and boil down to a volume of 5 to 10 ml. Remove and wash down the cover and sides of the beaker with water. Evaporate uncovered and without boiling to fumes of sulfur trioxide, cover with a flat Tvatch glass, and allow to fume for 3 minutes. If the solution becomes slightly tan or brownish from the presence of some organic matter, add a small pinch of ammonium persulfate to destroy this organic matter and allow the solution to fume an additional minute. Remove, allow to cool, wash down the sides of the beaker with water and evaporate uncovered to fumes of sulfur trioxide. Then cover with a flat watch glass and allow to fume again for 3 minutes. Remove and allovr-to cool. iidd 10 ml. of water to the first beaker, swirl to mix, immediately add 5 drops of thioglycolic acid, and swirl to mix. Proceed in a like manner with any remaining solutions. Transfer each solution to a 50-ml. volumetric flask, quantitatively, with the aid of water. Swirl to mix and cool. The volume in each flask should be approximately 45 ml. Proceed in accordance with the method described above for the preparation of a calibration curve for tin. Convert the photometric readings for the sample to milligrams of tin by means of the calibration curve. LITERATURE CITED
Am. SOC. Testing Materials. “.ZST1\I lIethods for the Chemical iinalysis of Rfetals,” p , 12, 1950. Clark, R. E. D., Analyst, 61,242 (1936); 62,661 (1937). de Giacomi, R., Ibid., 65,216 (1940). Kenyon, D., and Ovenston, T. C . J., S a t u r e , 167, 727 (1951). Rodden, C. J., Editor-in-Chief, “Analytical Chemistry of the Manhattan Project,” p. 377, Sew I-ork, hIcGraw-Hill Book Co., Inc., 1950. Stone, I.,IND. ENG.CHEV.,; 1 - i . 4 ~ . ED , 13,791 (1941). Williams, F. R . , and Whitehead, J., J . A p p l . Chem. ( L o n d o n ) , 2,
213 (1952). RECEIVED for review . 4 p d 21, 19.53. Accepted December 21, 1953.
Spectrochemical Determination of Germanium in Silicates P. G. HARRIS Department
of
Geology, University of Leeds, Leeds, England
I
S AN investigation of germanium-silicon ratios among coexisting silicates, it was found necessary to develop a quantitative spectrochemical method, capable of the determination of germanium contents of the order of 1 p.p.m. in mineral samples of less than half a gram-Le., 0.5 y of germanium. Previous methods using the cathode excitation of solid samples in the direct current arc ( 4 , 9) proved insufficiently sensitive even with an intermittent arc, while such methods as feeding into the arc large amounts of sample mounted on paper strips ( 8 ) , or the distillation of the sample from a furnace into the arc ( 7 ) , required larger amounts of sample than were available. General methods of chemical enrichment, in which several elements are coprecipitated and examined spectrographically ( 6 ) ,have been of limited sensitivity when applied to germanium. 1
Present addiess Dominion Laboratory, Wellington, S e u Zealand
Specific methods of enrichment usually involved the distillation of germanium as chloride, and its precipitation as sulfide, prior to its spectrographic determination ( 1 , 3). Geilmann and Brunger (3) could detect 0.25 y of germanium in this way in a semiquantitative examination. The present method differs from earlier enrichment methods in the choice of carrier for the coprecipitation of germanium sulfide, and in the choice of internal standard. The sensitivity (0.05 y ) is much greater than in other enrichment methods being of the same order as that found in the cathode excitation of solid samples [l p.p.m. in a 50-mg. sample, or 0.05 y (411. SPECTROGRAPUIC EXAMINATION
Source, Emitator Unit (Bolidens Gruv A.B., Sweden). Electrodes, 0.25-inch purified carbon rod (not graphite).
138
ANALYTICAL CHEMISTRY
Upper cathode pointed. Lower anode with cavity inch in diameter, '/e inch deep. Excitation conditions, 30-second exposure a t 7 amperes direct current (200-volt source). Optical conditions. Intermediate image produced on a diaphragm which passed central portion of arc only, and aperture focused on prism. Seven-step sector mounted immediately before slit. Slit width 0.03 mm. (nominal). Spectrograph, Hilger large quartz-glass model (Type E). Plates, Ilford Chromatic and Long Range Spectrum. Plate density measurement, Hilger nonrecording microphotometer. DETAILED PROCEDURE
Take enough powdered mineral to contain 0.1 to 2.0 y of germanium to fumes with hydrofluoric and sulfuric acids, and then to dryness twice with sulfuric acid, exercising care to remove all traces of fluorine. Dissolve the residue in the minimum amount of water and wash into an all-glass distillation apparatus of about 15-ml. capacity. Solution of the residue is assisted by prior warming with a few drops of sulfuric acid. Add 1 ml. of concentrated hydrochloric acid and distill carefully in a stream of air, collecting the distillate under water made ammoniacal, in a small conical centrifuge tube. (In practice, all the germanium was distilled when the distillate had neutralized 8 drops of concentrated ammonia.) Add 2 ml. of tin solution (E 500 y of tin) to the contents of the centrifuge tube together with 3 to 5 drops of sulfuric acid, and pass hydrogen sulfide through the solution. Leave corked overnight. Centrifuge, and decant off the supernatant liquid. Add 3 drops of ammonia and 3 drops of 6% hydrogen peroxide to dissolve the precipitate and transfer the resultant solution dropwise to the warmed electrode. Using the sample electrode as anode and a pointed upper cathode, arc for 30 seconds a t 7 amperes (200-volt source.) The separations, a t a constant density of 0.6, of the blackening curves (log Ill0 against log relative exposure) (6) for the lines Ge 3039.06 A. and Sn 3032.77 A., are referred to concentration curves, previously prepared from standard solutions, covering the range 0.1 to 2.0 y of germanium, precipitated with 500 y of tin and treated as described. SOLUTIONS
Germanium,1 ml. = 200 y . Dissolve 72.0 mg. of germanium dioxide in a few milliliters of water made alkaline with ammonia. Acidify and dilute to 250 ml. with 2% sulfuric acid. This solution may be further diluted with 2y0 sulfuric acid to give solutions in which 1 ml. = 20, 2, and 0.2 y of germanium. Tin, 1 ml. = 250 7. Dissolve 387 mg. of ammonium chlorostannate [(NH&SnCle] in dilute hydrochloric acid and make up to 500 ml. (to contain about 2% hydrochloric acid) DISCUSSION
I n earlier investigations (3) the chloride had been distilled from
a hydrochloric acid solution of optimum acidity of 3 to 4N, in a stream of chlorine t o prevent distillation of arsenic. In the absence of arsenic, air and not chlorine was passed through the distillation apparatus. With this condition, complete distillation of 0.1 y quantities of germanium did not occur until hydrochloric acid appeared in quantity in the distillate. This may have been due to the hydrolysis of germanium chloride on the walls of the apparatus, and was overcome by continuing distillation until constant boiling acid was coming over. The distillate was collected under water or weak ammonia to prevent volatilization of the germanium from the distillate. To obtain complete recovery of the germanium in as small a volume of distillate as possible, it was necessary to keep the amount of original solution to a minimum. Using the all-glass distillation apparatus of 12to 15-ml. capacity the final distillate never exceeded 10 ml. There was no loss of germanium on distillation, within the limits of spectrographic estimation. Four replicate solutions, each containing 0.4 y of germanium precipitated without prior distillation, returned an average content of 0.40 y . Four similar solutions, after distillation, returned an average of 0.41 y. In the
preparation of standard working curves the germanium solutions were not distilled each time but were coprecipitated with tin and treated subsequently as described. The sulfide precipitate was very finely divided when first formed but flocculated on standing, and was then readily separated from the liquid by centrifugation and decantation. Both germanium and tin oxides have similar volatility, ionization potential, etc., and appeared suitable for comparison. In addition their similarity in chemical behavior facilitated the chemical enrichment. The lines Ge 3039.06 A. and Sn 3034.12 A. seemed especially suitable for comparison by virtue of their closely similar excitation potentials. Unfortunately, under the exposure conditions necessary for maximum sensitivity of germanium estimation, and a t the concentrations of tin necessary for coprecipitation, the line Sn 3034.12 A. was too intense, and the line Sn 3032.77 A. was used instead. With the short exposures general background was small, while the unsymmetrical background of the Sn 3032.77 A. line due t o the 3034.12 A. line was also small a t the steps measured. Therefore no correction for background was made a t the concentrations examined. At high concentrations (above 2 y of germanium) the absolute intensity of the tin spectra seemed enhanced and this, together with the added background from the Sn 3034.12 A. line, may have caused the slight flattening of the working curve a t high values. Over the working range of 0.1 to 2.0 y the curve was linear. A comparison of alternating current arc, anode, and cathode excitation (all a t 7 amperes and 220 volts) showed anode excitation t o give far more reproducible results and equally good sensitivity. The use of lower voltages and current gave no appreciable increase in reproducibility or sensitivity. With anode excitation (7 amperes, 220 volts), a moving plate showed complete removal of germanium and nearly complete removal of tin in the first 5 seconds of exposure, while the last traces of tin were removed in 20 to 30 seconds. Subsequent exposure times were set at 30 seconds. Wandering of the arc was eliminated largely by the use of a pointed upper cathode. Since the first 5 seconds of excitation were so critical, initiation of the arc by momentary contact was undesirable. In lieu of an automatic triggering device, the arc gap was set, and the arc initiated by touching with a third electrode. REPRODUCIBILITY AND SENSITIVITY
The lower limit for quantitative estimation was less than 0.1 y of germanium, while the Ge 3039.06 A. line was visible a t concentrations of much less than 0.05 y. Reproducibility was of the order of &lo%. Replicate analyses of a rock (pitchstone, Glen Shurig, Arran, Scotland) showed 1.62, 1.40, 1.27, and 1.60 p.p.m. of germanium (1.47 i 0.15 p.p.m.), while the glassy base of the pitchstone which should be very similar contained 1.57, 1.63, 1.59, and 1.40 p.p.m. (1.55 f 0.09 p.p.m.). A further pitchstone (Judd's No. 1 dike, Arran) contained 1.47, 1.50, 1.72, 1.39, 1.53, 1.37, and 1.56p.p.m. of germanium (1.50 i- 0.11 p.p.m.). Two flue dusts kindly provided by H. J. Cluley (Research Laboratories, The General Electric Co., Ltd., Wembley, England) and analyzed by him using his absorptiometric method ( d ) , were examined by this spectrochemical method.
Absorptiornetric analysis Spectrochemical analysis
(H.J.C.) (P.G.H.)
Germanium, % A R 0.021 0.70
0.77
0.025
The results Cali be considered reasonably satisfactory in view of the thousandfold dilution necessary to bring the samples within the working range of the spectrochemical method.
V O L U M E 2 6 , NO. 4, A P R I L 1 9 5 4 ACKNOWLEDGiMENT
The author is indebted to W-.Q. Kennedy, Henrich Keumann, and Lars Lund of the Department of Geology, Leeds University, and to H. J. Todd and J. A. Ritchie of the Dominion Laboratorv. _. their advice and help. LITERATURE CITED
Breckpot. R., Ann. soc. x i . Brztselles, 55B,160-73 (1935). Cluley, H. J., And& 76, 523-30 (1951). Geilmann, W., and Brunger, K., 2. anory. u . aZli]em. Chetn., 196, 312-20 (1931). Goldschmidt, V. AI,, and Peters, C., 4-uchr. Ges. Wiss. Gottingm, Math.-physik. KL., 141-66 (1933).
739 (5) Mitchell, R . L., Commonwealth Bur. Soil Sci., Tech. Commun. No. 44 (1948). (6) Mitchell, R. L., and Scott, R. 0.. J . SOC.Chem. I d . (London), 66,330-6 (1947). (7) Preuss, E., 2. angew. Mineral., 3, 8 (1940). (8) Rusanov, A. K., and Bodunkov, B. I., Zacodskaya Lab., 9, 183-6 (1940). (9) Wickman, F. E., Geol. Fdren. i Slockholm Farh., 65, 371-96 (1943). RECEIVED for reriew August 24, 1953. .4ccepted December 31, 1953. This work was done during the tenure of a National Research Scholarship, administered by the Department of Scientific and Industrial Research, S e w Zealand.
Study of Osmium and Ruthenium A. D. WESTLAND and F. E. BEAMISH University of Toronto, Toronto, Ontario, Canada
THE
' only recorded methods (4, 9) for the quantitative separation of osmium and ruthenium involve selective oxidation by nitric acid to form octavalent osmium oxide. The methods possess one or both of the following disadvantages: The nitric acid must be removed from the ruthenium fraction before ruthenium (VIII) oxide can be volatilized quantitatively and the evolution of nitric oxide in distillations when reducing agents are present may cause low osmium results (8). It was desirable to devise entirely different methods of separation and since osmium and ruthenium are usually present as minor constituents, the new methods should be applicable t o micro amounts of the metals. It was known that when ruthenium(VII1) oxide is passed into a solution of hydrogen peroxide, the resulting solution can be boiled without loss of ruthenium. A similar solution of osmium was found to yield osmium(T'II1) oxide upon heating and no osmium could be detected in the residual liquid after boiling for a considerable time. This process forms the basis of the separation procedures described. The authors were able to analyze solutions contaiuing both metals by existing gravimetric and by modified colorimetric methods
crop in 0.L)- hydrochloric acid, filtering off a small insoluble residue, and diluting with more of the acid to 500 ml. A gravimetric analysis of this solution by the thionalide method ( 7 ) gave a value of 0.2881 mg. of ruthenium per ml. Osmium. Ammonium chloroosmate salt was prepared according to the procedure of Gilchrist ( 5 )from osmium tetroxide supplied by Johnson, Matthey, and Mallory Co. The salt was analyzed by direct heating in hydrogen, followed by ignition in air. No residue remained after this treatment. The percentages of osmium in two crops of the crystals were 43.15 and 43.17, respectively. A solution calculated to contain 0.3998 mg. of osmium per ml. was prepared by dissolving 0.9721 gram of the first crop in 0.5N hydrochloric acid, filtering, and diluting to 1000 ml. with the same acid. Gravimetric analysis of this solution by the thionalide method (6) gave a value of 0.4012 mg. of osmium per ml.
APPARATUS
The distillation apparatus used was a modification of that used by Allan and Beamish ( 2 ) and is shown in Figure 1. The tnro receiving tubes were of 30- and 20-mm. diameter, respectively. Qualitative filtrate tests Fere carried out using the distillation apparatus shown in Figure 2. Weighings were made using a Sartorius projection reading and an air-damped microbalance and transmittancies were measured with a Lumetron 402EF colorimeter using 20-mm. rectangular cells.
-
I I
PREPAR4TION OF S T 4 Y D A R D SALTS AND SOLUTIOILS
Ruthenium. Ruthenium sponge supplied by the Baker Platinum Co. was esamined spectrographically and was found to contain a trace of iron. The sponge was brought into solution by dry chlorination a t a temperature of 650" to 700" C. over a period of 16 hours. The metal was contained in a porcelain boat and was covered m-ith fine sodium chloride crystals to a depth of about 3 mm. After allowing the boat and contents to cool in an atmosphere of chlorine they were transferred, along with a tube sublimate, to a solution of 20 ml. of concentrated sulfuric acid in 25 ml. of water, rinsing with 6 S hydrochloric acid. The solution was filtered and evaporated until dcnse fumes were evolved. The filtration separated insoluble chloride which was rechlorinated after reducing to the metal in hydrogen. Ammonium chlororuthenate was then synthesized by the method of Rogers, Beamish, and Russell ( 7 ) and analyzed by direct ignition in a current of hydrogen. The percentages of ruthenium found in two crops of crystals were 30.24 and 30.43, respectively. A solution was prepared by dissolving 0.4781 gram of the first
\
i
. . -
Figure 1.
Distilling Apparatus
Filtrate Test. Filtrates from both ruthenium and osmium precipitations and other solutions were examined for the presence of the metals by means of the following procedure. The filtrate or solution was placed in vessel A of the small distillation apparatus and 20 ml. of 70 to 72% perchloric acid were added. Fifteen milliliters of a 10% solution of thiourea in 6N hydrochloric acid were placed in receiver C and an ice bath was placed around trap B. The content of A was boiled until dense fumes were evolved, the water collecting in B. Throughout the distillation a stream of air was draR7-n through the system. After a few minutes' further heating the vessel B was brought to boiling for a few seconds. A blue or red color appearing in the thiourea solution indicated the presence of ruthenium or osmium, respectively. As little as 8 y of osmium and fewer still of ruthenium could be detected in this way.
