ANALYTICAL EDITION
May, 1944
ghss fragments to a weighed filter crucible and obtain the weight of the whole after drying. The w e i g h t of t h e osmium tetroxide used to pre are the stronger soktion is thus obtained by difference. THIOUREA,10% aqueous solution. POTASSIUM PERMANGANATE, 5 % solution. HYDROCHLORIC ACID-SULFUR DIOXIDE SOLUTION, 1 F! F! M. OSMIUM to 1 hydrochloric acid freshly eatuFigure 2. Extinction-Concentration rated with sulfur Curves for Osmium Tetroxide-Thiourea dioxide. Solutions
PROCEDURE
Green fiitw Cenco. No P A. Solutions contained ' 8 mi. of '6 N HCI and 0.5 ml. of 10% thiourea in 95 ml.1 toom lemperatuce 8 . 0 1 0 4 solutions belted with 10 mi. of 6 N HCI sattmled with SO, allowed lo stand 15 minutes at room tem erlture 0.5 mi. of 10% thiourea solution adbed, and whole diluted 40 95 mi. with water.
The sample solution should have a volume such that when it is ready for distillation, after addition of nitric acid and Dcrmanganate, the'total volume is less than 50 or 60 ml. Chlorides must be absent, and if permanganate oxidation is necessary the solution should be about 1 N in sulfuric acid. Transfer the solution to the distilling flask, and if ferrous iron or other reducing substances are present, add potassium permanganate solution until an excess of a drop is present as indicated by the color change; avoid getting permanganate on the neck of the flask. Next add approximately 50 mg. of ferrous ammonium sulfate hexahydrate to destroy permanganate and higher oxid'es of manganese. The volume of the solution a t this point should be 35 to 40 ml. Add a few small grains of pumice, connect the flask to the condenser, and heat the solution slowly to near the boiling point to make it certain that higher manganese oxides have been brought completely into solution. Dip the end of the condenser into 10 mi. of hydrochloric acid-sulfur dioxide solution contained in a 100-ml. praduate, the upper half of which has been cut off (a large vial or test tube marked to indicate 20 ml. may be substituted). Add 15 ml. of concentrated nitric acid through the inlet tube of the flask and distill at such a rate that 10 ml. of distillate are collected in 10 to 15 minutes. Transfer the distillate mixture to a 25-m1. volumetric flask, rinsing the condenser and receiver with a few milliliter3 of water, add 0.50 ml. of thiourea solution, and make up to the mark with water. Determine the transmittancy of the solution after 5 minutes (longer standing does no harm), using preen light. In constructing the standard curve add 0, 25, and 50 micrograms of osmium as the tetroxide to distillates obtained from osmium-free nitric acid mixtures as already described. If the amount of osmium is likely to be less than 10 micrograms, use 5 ml. of hydrochloric acid-sulfur dioxide solution contained in a 25-ml. graduate for collecting 10 ml. of the distillate. Add 0.3 ml. of thiourea solution, read the volqme of the solution in the graduate (which has bccn checked for accuracy), and determine the tronsmittancy as described above. DETERMINATION OF OSMIUM IN METEORIC IRON
The following procedure waa used in determining osmium in the Cation Diablo siderite. A 1-gram Rzmple was heated near the boiling point with 10 ml. of 6 N sulfuric arid in an Erlenmeyer flask until there was practically no further action. The solution was decanted from the unattmked samplo and reserved. The remainder of thc metal was dissolved in 10 ml. o f hot 6 N hvdrorhloric arid. The solution was then treatcd with 10 ml. of 6 N sulfuric acid and evaporated to furnos of sulfuric acid. The evaporation to fumes was rcpeated after dissolving the salts in watcr. The residue was then heated with about 10 ml. of water to bring all but a small amourit of insoluble material into solution. This solution 'and the reserved sulfuric acid solution were transferred to the distilling flask and the ferrous iron was oxidized with permanganate. After
343
addition of nitric acid, the solution was distilled and osmium was determined as described above (5 ml. of hydrochloric acid-sulfur dioxide solution were used to collect 10 ml. of distiljate). The small amount of insoluble material remaining in the solution after distillation was collected in a small porous porcelain filter crucible, the bottom of which had been covered with a thin byer of quartz powder to farilitate the subsequent removal of the insoluble material. The collected material was dried by washing with acetone, transferred t o a nickel rrucible, mixed with 1 gram of sodium peroxide, and heated a t low redness for 30 minutes. The melt was extracted with 20 ml. of water and the solution heated near the boiling point to decompose peroxide. The solation was transferred to the distilling flask and treated with 10 ml. of 6 N sulfuric arid. Approximately 50 mg. of ferrous ammonium sulfate were added and the solution was heated to destroy nickelic oxide, Nitric acid was then added and the distillation made as already described. No osmium was detected in this dis-
tillate.
The osmium content of the C d o n Diablo meteorite thus found is 2.5 p.p,m. Since the method tends to give slightly low results, this value may as well be rounded off to 3 p.p.m. The Noddacks found 3 p.p.m. of osmium in this meteorite, and GoldSchmidt and Peters reported an approximate osmium content of 5 p.p.m. LITERATURE ClTED (1) Chugaev, L.A.,C m p t . rend., 167,235 (1918); Z . anorg. d l g e m . Chem., 148,65 (1925). (2) Gilchrist, R., Bur. Standards J. Research, 6,421(1931). (3) Goldsrhmidt, V. M.,and Peters, C., Nachr. Ges. wi8S. GBttingen. Math.-physik. Klasse, 1932,377. (4) Noddack, I., and Noddack, W., Naturwissenschujten, 18, 757 (1930);Z.physik. Chem., 154A. 207 (1931);Zbid., BodasteinFestband, 1931,890; Svenqk Kem. Tid.. 46,173 (1934). ( 5 ) Robinson, W. O., Dudley, H. C., Williams, K. T.. and Byera H. G., IND.ENG.CHEM.,ANAL.ED.,6,274 (1934). (6) Russell, J. J , Beamish, F. E., and Seath, J., Ibid., 9,475 (1937)
A
Funnel for Filling Capillaries
ALFRED 0. WALKER, National Aluminate Corp., Chicago, 111.
F
ILLING the capillary tubes used for supporting samples in x-ray diffrsction cameras is a tedious and time-consuming procedure. The funnel described and illustrated here greatly simplifies this operation. It is constructed of brass, although other materials could be used. The dimensions of the taper are determined by the size of the capillaries being filled. Plastic capillaries can be wedged into the tapered hole of the funnel firmly enough to stay in place during the filling operation. Glass capillaries must be held in with a slight pressure of the little finger, with the funnel held between the thumb and forefinger. The ground sample is placed in the funnel, and the top edge of the cap is rubbed with a serrated surface such as the side of a pair of tweezers or a dull file in order to shake the powder down into the capillary. If the hole plugs up, a wire ran be used to clear it. Hygroscopic samples can be dried in the funnel in an oven, broken up with a wire, and introduced into the capillary before they have a chance to pick up moisture.
