SYNTHESIS, STRUCTURES, AND PROPERTIES OF

PLATINUM METAL TELLURIDES1

W. O.J. GnoBNnvor,o Mnrlnn,2 Queen's Uniaersily,Kingston, Ontorio, C anada.

AssrneclTellurides of all platinum metals have been synthesized and characteriz*dby x-ray ar;.d

optical methods. Ditellurides of ruthenium, osmium, rhodium, and iridium have pyrite type

structures, ditellurides of platinum and palladium are of the cadmium iodide type, iridium

and palladium monotellurides have nickel arsenide type structures.

INtnouucrroN AND AcrNowrBncEMENTS

Only one platinum metal mineral, sperrylite (PtAs) is known to occurwith certainty in the Sudbury ores. Since tellurium is one of the products

recovered from the ores and no tellurium-bearing platinum metal min-

erals have been reported, the synthesis of the tellurides of the platinummetals was undertaken in order to obtain data which might eventuallybe of mineralogical, and therefore of geochemical, interest. More speci6.-cally, their synthesis was performed so that optical and crystallographicalobservations derived from them would be of assistance in their possible

ultimate detection in polished sections of the ores.The work is limited to a description of the products obtained by dry

fusion of the metals in various atomic proportions in a vacuum. Someobservations are included on phase relationships, especially in the systempalladium-tellurium.

The research program was carried out in the Iaboratories of the De-partment of Geological Sciences, Queen's University, Kingston, underthe supervision of Dr. J. E. Hawley. The author is indebted to Dr. L. G.Berry for his suggestions during the preparation of the manuscript.

SvNruBsrs

In principle, two methods are available for the preparation of com-pounds of the platinum metals with metalloids such as tellurium:

(1) By a "wet" procedure; for instance through the reaction of hy-drogen telluride (HrTe) on a platinum metal salt in solution, and

(2) By a "dry" procedure; by direct fusion of the weighed constituents.The latter method is the more favorable for our purposes. When

homogeneous (one phase) products are obtained, it is not necessary to

I Extracted from a portion of an unpublished Ph.D. thesis by the author: The Geo-

chemistry of the Platinum Metals with Respect to Their Occurrence in Nickeliferous Sul-

phide Deposits-Queen's (Jni,versity, 1954. This work was carried out with the aid of a

scholarship from the Research Council of Ontario (1953).2 Now with McPhar Geophysics Limited, 36 Cranfield Road, Toronto, Canada'

646

PLATI NUM METAL TELLU RI DES

analyze the product since we may assume that it will have a compositionequal to that of the charge which is weighed out in definite stochiometricproportions. Otherwise hindersome, secondary reactions such as hydroly-sis, oxidation, and disproportionation can be avoided or controlled byheating the charges in evacuated and sealed tubes.

As the platinum metals melt at high to very high temperatures andtellurium melts at a relatively low temperature (452o C. at atmosphericpressure), the reactions take place in the heterogeneous systems solid-vapor or solid-l iquid. It is thus of importance that the solid phase bepresent in a finely divided state. For that reason, the platinum metalswere used in either their "sponge" or "blackt'form. The chemicals usedfor this work are listed in Table 1.

Charges oI 1.2 to 0.5 gm. were prepared by weighing out the platinummetal and the powdered tellurium in proportions, corresponding to the

Tesr,B 1. Cnnlrrcnrs Usnl ron FusroNs

647

Te, metallic, coarsely crystalline, Fisher, C. P.Pd, sponge, Falconbridge .062/6 other PM's; .009/q Fe, .026/e SiO2; traces of

Ni and Ag.Pt, sponge, Falconbridge .042/6 other PM's; .042/6 SiOz; traces of Fe and Ni.Ir, sponge, Falconbridge .14/6 other PM's; .72/6 Ni, .03% F e, .73/s Si.Rh, sponge, Falconbridge .23/6 other PM's; .07/eNi, .0770 Fe, trace of Ag.Ru, sponge, Falconbridge .0570F.h, .1370N| .05ToFe; traces of Ag, Pt, Pd.Os, black, Johnson, Matthey & Mallory, spectrographically pure.

expected formulae of the compounds to be prepared. The powders weremixed and inserted into Vycor or Vitreosil glass tubes 7-8 mm. bore, 25cm long sealed at one end. The tubes were then attached to a vacuumpump by airtight rubber tubing and collapsed in the center by heatingwith an oxygen-hydrogen flame until only a small passageway remained.After evacuation and with the pump running, the narrow constrictionwas sealed with the flame. During the sealing operation, small amountsof tellurium sublimate from the charge, and condense immediately abovethe sealed join. For this reason a slight excess of the metalloid was gen-erally added over the calculated amount.

As the reactions in question are exothermic in character, all mixedcharges were first brought to reaction by inserting the sealed tubes in asteel shell and heating this slowly in a furnace from room temperature toapproximately 850o C. They were left at this temperature for 2 hoursand then allowed to cool over a period of 12 hours in the furnace.

With palladium and platinum compounds, the reaction product iscompact and apparently homogeneous. In such cases the tubes were

648 W, O, J. GROENEVELD MEIJER

broken open and the nuggets were sawed in halves. One half was mountedin bakelite for polished section study, the other reserved for *-ray ex-amination. With compounds of the other platinum metals the productswere generally loosely sintered and very fine-grained. Good r-ray photo-graphs were obtained from these powders. In order to increase the grainsize, the sintered fusion products were reground and sealed anew inevacuated silica glass tubing with the addition of a small amount oftellurium. Since the reaction had clearly taken place, the tubes were nowheated for 24 or more hours over the hottest gas flame obtainable witha Mecker burner. In some instances, the grain size did increase so thatwith repetition of the fusion and grinding processes, polished sectionscould be prepared. Since the products were still porous in those cases,they were impregnated with a solution of bakelite in acetone under re-duced pressure.

All r-ray photographs were made by the Debye-Scherrer powdermethod using a camera with an internal diameter of 57.3 mm.l Full cor-rection for film shrinkage was applied. The fusion products belongedeither to cubic (pyrite type) or hexagonal (niccolite and cadmium iodidetypes) systems. After indexing the films by standard methods outlined inHenry, et al. (195I), unit cell dimensions were calculated from the moreprecise back reflections and the interplanar spacings calculated from thesedimensions.

INotvtouar Pnonucrs

Ruthenium Ditellurid,e (RuTe)

Ruthenium ditelluride has been synthesized by Thomassen (1929) bydry fusion in vacuum. The structure was determined as being that ofpyrite with oo : 6.360 + .002 A. Wiihler, et at. (1933) also synthesized andanalyzed the compound by heating ruthenium trichloride with an excessof tellurium in a porcelain boat in a carbon dioxide stream at atmosphericpressure.

In this series of syntheses the compound was prepared by fusing themetals in their correct atomic proportion. The black sintered productshowed no crystal forms under the binocular microscope. By refusion invacuum, a coarser grained product was obtained. Thomassen (1929) re-ports that the compound melts at a temperature, estimated at between400 and 6000 C. At no time was a liquid phase observed here althoughmuch higher temperatures were applied.

Under the microscope, in polished section, the following propertieswere determined on the porous subhedral aggregate: It is isotropic, fine-grained and has a high (F) Talmage hardness. The color is white, the

I Using CuKal : 1.54050 A. (Ni filter).

PLATINUM METAL TELLURIDES 649

reflection is strong. Etch reactions performed after Short (1940) are nega-tive with KOH, KCN, HCl, and FeCh. With HgClr an iridescent, inpart grey, stain is produced which is easily rubbed off. HNO3 producesslight effervescence between grain boundaries; a brownish stain withsome iridescent colors is produced. The efiects are probably due to tel-lurium, which is found sparsely in the section.

An excellent powder diagram (Table 2) was obtained from which all

Tenr-n 2. RurnnNruu Drrnllunron-RuTez: X-nev Powarn Der.t

Cubic, Pyrite Structure; ao:6.377 + .0O1 h

d (meas) d (ca,lc) d (meas) d. (calc)

12

i

109

12

10

+

72I2

L

+

22o

55

1 1 12002102 t l2203003 1 1222320321400331420421332422333520J Z \

3 . 7 03 . 1 62 8 22 . 5 72 2 42 . 1 11 .9051.823r . 7 5 21 6941 .5821.4661 . 4 1 81 .386I . .1.) .)

.2961 1 1

. 1 8 1l6l

3 .683 1 92 . 8 52 . 6 02 . 2 52 . 1 21 . 9 21 .84t . 7 7r . 7 01 5931.+63| . 4 2 61 .3901 .3591 . 3 0 11 . 2 2 71 . 1 8 31 . 1 6 3

1 . 1 2 61.0601 .0461 . 0 3 31.008

.972

.96r

.951

.940

.92r

.884

.877

.8680

.8530

.8319

. 8 1 8 1

.8117

.7989

. l l J z

62z

4141 iA

311n

52

107862

4 0 r . 1 2 7600 1.062610 1 .049611 1 .034620 1.008533 .973622 .962630 .951631 .9+04M .92r640 .884720 .87772r .8686+2 .85373r .830650 817732 .810800 .798820 .774

l ines could be indexed. The unit cell edge with ao-6.377 + .001 A is slightlylarger than that obtained by Thomassen (1929).

Osmium Ditelluride (OsTez)

Osmium ditelluride has been synthesized by Thomassen (1929) by dryfusion of the elements in vacuum. The substance was found to have acubic pyrite-type structure with ao:6.369-1.003 A.

In this work the compound was synthesized in the usual manner. Itwas not possible to obtain a polished section from the loosely texturedand very fi.ne-grained fusion product. Thomassen (1929) reports that thecompound melts at a temperature estimated between 500 and 6000 C.No such melting was observed in this work. At high temperatures, the

650 W, O, J. GROENEVELD MEITER

compound dissociates and tellurium condenses at cooler portions of theevacuated tube.

The powder photograph could be readily indexed on the basis of acubic unit cell with ao:6.39&-1.001 A. The photograph shows one extraIine (d:2.07,Ta"ble 3) which corresponds to the strongest osmium line

T.ter,B 3, Osuruu Drrru,uurn OsTez: X-nev Pomrn Dere

Cubic, Pyrite Structure; oo:6.398s+.001 A

d (meas) d. (calc) d (meas) d (calc)

1

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42233352052I440J J I

442

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3 . 6 93 . 2 02 . 8 62 . 6 12 . 2 6

1 .0381 . 0 1 0

.973

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.8465

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.8192

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.396

.362

.306

.230

.187

.168

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and whose presence is not unexpected, considering the observed dissocra-tion of the compound. The intensities of the other lines are quite similarto the corresponding lines of ruthenium ditelluride.

Rhod.iurn (Di?) T elluride (RhTer+J

Some controversy exists in the literature as to the composition ofrhodium-tellurium compounds. Wiihler, et al. (1933) synthesized andanalyzed a ditelluride. Strangely enough, the authors remark, no com-pound analogous in composition to RhzSes is formed. Biltz (1937) re-analyzed the compound and found a formula RhTer.a;. He reports thatthe substance has a pseudo-pyrite structure. This structure was reportedfor RhSez,re, where pyrite lines were split into several distinct lines,

PLATLNUM METAL TELLLIR]DES 651

However, Biltz (1937) only reports that "slight line splitting is likely"for RhTer.nr, and no further x-ray data are given for the compound.

A telluride of rhodium was prepared from a charge of the elements,mixed in the atomic proportion of RhTez.s. After several heat treatments,a fine-grained product was obtained, which was rendered coherent by anexcess of tellurium. The compound is isotropic, its color is white in re-flected light and slightly darker than the tellurium with which it wasintergrown. The Talmage hardness is high (F) . Etch reactions are nega-tive with KOH, KCN, FeCl3, and HCI. With HNOa faint intergranular

T.qrr.B 4. Ruoorulr (Dr?) T rlunroB-RhTez+, X-nav Pomnn Dera

Cubic, Pyrite Structure; ao:6.428+.001 A

d (meas) I d, (meas) hkl d (calc)

z109

101

38

z

A

z

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461

2002 to211220311222320J Z I

40042042133242233352052140600

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2 . 9 11 . 8 3r . / o1 . 7 01 . 5 91 . 4 3t . 3 9 41 . 3 6 01 .304| . 2 3 11 . 1 8 71 . 1 6 6| - r 2 81.068

3 . 2 22 . 8 72 . 5 32 . 2 71.940I .857r . 7 8 21 . 7 1 91 .6081 .4381.4031 . 3 7 01 3121.2381 . 1 9 31 . 1 7 31 . 1 3 71 . 0 7 1

2 1 .0525 1 .0391 1 .0063 .978| .9664 .9584 .946r| .9264+ .88986 .88288 .87443 .8592

10 .83688 .82299 .81616 .80356 .77975 .7755

610 1 .058611 1.043620 r.0r7533 .980622 .969630 .958631 .948444 .928640 .891720 .88472r .875642 .86073r .837650 .823732 .816800 .804820 .780821 .774

efiervescence was observed which is likely due to the presence of tel-lurium.

An excellent r-ray powder photograph was obtained with very clearlyresolved Kar and Ka2 doublet in the back reflection region. No line split-ting of any kind was observed and all lines could be indexed on the basisof a cubic unit cell with oo:6.428X.001 A (Table 4). The intensitydistribution is very similar to that of ruthenium telluride and a pyritestructure is clearly indicated for this compound. There is thus no evi-dence to advance in favor of a so-called pseudo-pyrite structure al-though the lack of tellurium lines on the powder photograph, which was

652 W. O. J. GROENEVELD MEITER

taken before the compound was prepared for polished section by refus-ing it with excess tellurium, does tend to corroborate the RhTe 21., for-mula.

Irid,ium (Di?) T ellurid,e (IrT ez+)

Wiihler, el aI. (1933) report the existence of two iridium tellurides:IrTe2 and IrTes. Biltz (1937) analyzed a compound, saturated withtel-lurium and found IrTer sg. He includes the substance in the pseucio-pyrite structural classification, although it is stated that a slight splittingof pyrite lines is only "likely." No further fi-ray observations are men-tioned.

In this work an iridium telluride was prepared from the charge IrTer.s.As with osmium, this compound loses tellurium at higher temperatures.A satisfactory polished section could not be prepared of the friable,sintered product.

The powder photograph of the product was easily indexed on the basisof a cubic unit cell with ao:6.411+.002 A. No efiects of l ine splitt ingcould be observed in the very clear film. The intensities of the Iines(Table 5) are very similar to those measured in the other compounds ofthe platinum metals already described with pyrite structures.

Irid.ium M onotellurid,e (IrTe)

In the preparation of iridium ditelluride it was noticed that the productlost tellurium at higher temperatures. The r-ray powder photographdid not show iridium lines and as the diagram seemed amenable to index-ing on a hexagonal Iattice of the niccolite type, a fusion product was pre-pared of the composition IrTe.

Iridium monotelluride formed a friable fine-grained sintered product.It was impossible to prepare a polished section of the compound; at-tempts to fuse it in a hollow carbon electrode in the arc resulted in itsdissociation to metallic iridium.

The powder photograph was indexed (Table 6) on the basis of an ortho-hexagonal uni t ce l l wi th oo:3.930 A, ca:$.336 A, and c:1.370. Af tera first trial indexing, more accurate interplanar spacings were obtainedwith the Philips cc-ray difrractometer on a few planes with 001, hk}, andhkl type indices.

P alladium Ditelluride PdTez

Thomassen (1929) prepared palladium ditelluride and found for it acadmium iodide type structure with ao : 4.028 !.003 A, c6 : 5. 1 1 8 + .004 A,and c:1.271. Wdhler, et al. (1933) prepared the ditelluride as the onlycompound in the system Pd-Te.

PLATI NA M METAL TELLU RI DES

T.qsr,r 5. Inroruu (Dr?) Tnr-r,unror-IrTe2.., X-n.lv Pownrn Dlre

Cubic, Pyrite Structure; ao:6.417+ .002 A

653

d (meas) d (calc) d (meas) d (calc)

25

27I2

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12Izi

J

z/

3 . 1 42 . 8 12 . 5 7z . z J

1 . 9 11 . 8 2I . / J J

1 . 6 9 21 . 4 2 21 . 3 8 31 .3501.2991 . 2 2 31 . 1 8 1r . l 6 tr . 1 2 6

200210211220J I I

22232032r420421

A n 1

333520521440

3 . 2 12 . 8 7z . o z2 . 2 71 . 9 3 41 . 8 5 11 .7801 . 7 1 51 . 4 3 31.4001 .3681 . 3 1 01 . 2 3 5r . t 9 11 . 1 7 1t . 1 3 4

1.0631.0481 .0361.009

. 9 7 5

.964

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600 1.070610 1.055611 1.041620 1 0r4533 .979622 .967630 .9s6631 .946640 .889720 .881721 .873642 .857731 .835650 .82r732 .815800 .802820 .778

A

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Tenln 6. Inroruu MoNorur,urror-IrTe: X-nev Poworn Der,q'

Hexagonal, niccoi i te structure; ao:3.930 A, co:5.386 A. c: l '37O

d (meas) h k . l d (calc) d (meas) h k l d. (calc)

J

I10

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5 . 2 93 .342 .832 .642 .09r .941 .8241 . 7 7 91.606r . 5 7 6r .4281 .339r .317r .2441 .2291 . 1 5 6

5 . 4 03 . 4 02 .882 . 6 92 . 1 1| . 9 6| .8471 . 7 9 61 . 6 2 51 .588r .437I . J + O

1 . 3 2 6r . 2 5 11 . 2 3 51 . 1 6 0

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654 W. O. J. GROENEVELD MEITER

In this work, palladium ditelluride was formed by fusing the elementsin the correct atomic proportions. Metallic nuggets were obtained whichwere homogeneous in all respects. The compound is coarsely crystallineand shows the excellent platy cleavage, peculiar to compounds with thesheetlike cadmium iodide type structure.

In polished section, palladium ditelluride is homogeneous. The com-pound is white, lighter in color and more creamy than native tellurium.It is very easily scratched with a steel needle (Talmage hardness B).The cleavage plane (0001) is not well developed but shows up by applica-tion of a sharp object. The compound is quite strongly anisotropic: bluishand yellowish colors are observed. The etch reactions are negative forKOH, HgCl2, KCN, and HCl. FeCls forms a brown stain in two to fiveminutes. With HNOB faint effervescence was observed with rapid dis-coloration of the reagent droplet to orange brown; fumes stain slightly.In a fusion product of composition PdTe3, the ditelluride is seen withnative tellurium.

Interplanar spacings obtained from powder diffraction photographscheck well with those calculated from data presented by Thomassen(re2e).P alladium M onotellurid.e (PdTe)

Thomassen (1929) also prepared palladium monotelluride by dry fusionof the elements in evacuated tubes. For the compound a nickel arsenidestructure was found wi th oe:4.127 + .004 A, co:5.663+.005 A, andc : 1 . 3 7 2 .

The fusion product of palladium monotelluride forms a brassy com-pact product. In polished section it is very strongly anisotropic withcolors ranging from deep blue to yellow. Its color is creamy white, theTalmage hardness is C; no cleavage was observed, either in hand speci-men or polished section. The etch reactions are similar to those obtainedwith the ditelluride: negative with KOH, HgCl2, KCN, and HCI; FeChleaves after five minutes an orange-brown stain. A reaction occurs withHNOI but no effervescence was observed, the reaction droplet turns deepred-brown but no precipitate forms within 30 seconds as with PdTer.

Interstitially between the larger monotelluride grains, a small amountof a myrmekitic intergrowth of monotelluride and an isotropic (?) com-pound appears. This 6.ne-grained palladium monotelluride extinguishedparallel with the larger bounding crystals, which show sutured contactstowards the intergrowth. This texture is not likely eutectic in origin,rather does it appear to be a product of a peritectic reaction, e.g.:

PdTe 1".pt"tul f Pd1-."Te1-"rt1 : Pd11rT€1gs1arsy

PLATI NU M METAL TELLURI DES 655

A polished section was also prepared from a fusion product of composi-tion PdzTea. Macroscopically it is very similar to the ditelluride but underthe microscope, the product is seen to consist of two phases, one the ditel-luride, the other an exsolution product, deposited along (0001) directionsof the former. The latter is very fine-grained and differs from the mono-telluride and the ditelluride by the absence of strong anisotropism. Thisexsolution product was too fine-grained to be isolated for powder diffrac-tion work.

Thus, aside from PdTe and PdTe2, two other phases are indicated:one isotropic phase, occurring as a myrmekitic intergrowth with pal-ladium monotelluride and another fine-grained phase appearing as anexsolution product in PdTe2.

Interplanar spacings calculated for palladium monotelluride are verysimilar to those calculated from Thomassen's data 1929).

Pl,atinum Ditellurid,e (PtTer)

Roessler (1897) prepared platinum ditelluride by heating platinumr','ith an excess of tellurium in an open furnace. Wcihler, et al. (1933) alsoprepared and analyzed the compound. Thomassen (1929) synthesizedit from the elements and determined the structure. It has a cadmiumiodide type structure with @0:4.010+.004 A., co:5.201 +.005 A, andc:1.297. No other tellurides are reported by Wiihler or Thomassenalthough the latter attempted to prepare the monotelluride. Roessler(1897) reports the existence of PtTe and Pt2Te which he obtained bymelting the ditelluride in an oxidizing flame of a blowpipe on charcoal.

In this work the ditelluride was prepared in the usual manner. Itformed a sintered product after fusion; refusion at higher temperaturesyielded a product from which a satisfactory polished section could beprepared. No liquid phase was observed.

In polished section the aggregate of anhedral crystals takes on a goodpolish. The Talmage hardness is B. In reflected light PtTe2 is white, withthe same intensity of reflection as tellurium or slightly darker. It ismoderately anisotropic. Etch reactions with HgCl2, KCN, HCl, KOHand FeCla are negative. HNO3 produces locally slow intergranular ef-fervescence. HNO3 fumes tarnish the compound locally although some ofthese efiects are possibly due to small amounts of tellurium.

The r-ray powder photograph of PtTes is slightly diffuse. It is difficultto obtain a good mount of the compound due to its softness and flakynature. Measured interplanar spacings agree well with those calculatedfrom Thomassen's data 1929\.

W. O. J. GROENEVELD MEIJER

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PLATINUM METAL TELLU RIDES

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The dry fusion procedure of synthesis has been found successful forpreparing the following compounds:

RuTe2, OsTes, RhTe21', IrTe2a', IrTe, PdTez, PdTe, and PtTee.

Only palladium compounds form melts; other products do not melt invacuum over the hottest gas flame available-in contrast to publishedaccounts-indeed, they tend to dissociate at very high temperatures.

The platinum metal tellurides RuTe2, OsTe2, RhTe21o, and IrTe21,all belong structurally to the pyrite group. Their interplanar spacingsas well as the densities of their lines on tr-ray powder photographs areconsequent_ly very similar; the unit cell edges are within the range 6.377 <a036.428 A. The ditellurides of platinum and palladium are both hexag-onal and belong to the cadmium iodide type which is characterized by astrong cleavage parallel (0001). IrTe and PdTe have niccolite structures.Properties determined on all products are shown in Table 7.

RnlBnBNcns

Brr,rz, W. (1937): Notiz zu Selen- und Telleurverbindungen von Iridium and Rhodium.Z. anor g. al gem.. C hem., 253, 282-285.

Hrrnv, N. F. M., Lrrsox, H., & Woosrnn, W. A. (1951): Theinterpretation oJ cc-ray d.i.J-

frocli.on photo graphs. Macmillan & Co., London.Rorssmn, C. (1897): Uber Tellurverbindungen des Platins. Z. anorg. Chem.,15,405-411.Snonr, M. N. (1940): Microscopic determination of the ore minerals. 2nd ed., U. S. Geol.

Surt:., Bull.9l4.TrouessnN, L. (1929): Uber Kristallstrukfurtypen einiger biniirer Verbindungen der

Platinmetalle. Z. phys. Chem., 48, 277 -287.

Wcinr,nn, L., Ewer,o, K., & Kner,r,, H. G. (1933): Die Sulfide, Selenide, und Telluride dersechs Platinmetalle. Ber. Deu. Chem. Ges.,66, part II. Section B, pp. 1638-1652 .

657