Direct determination of submicrogram amounts of osmium and ruthenium in sulphide ores by neutron activation analysis

Direct determination of submicrogram amounts of osmium and ruthenium in sulphide ores by neutron activation analysis

Anafytiia Blsc&r Printed Chimica Ada Pudlishing Company, ii~ The Nethcrl&ds 357 Amsterdam DIRECT DETERMINATION OF SUBMICROGRAM AND RUTHENIUM IN S...

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Anafytiia

Blsc&r Printed

Chimica Ada Pudlishing Company, ii~ The Nethcrl&ds

357

Amsterdam

DIRECT DETERMINATION OF SUBMICROGRAM AND RUTHENIUM IN Sl_JLI’HID11= ORES RY ANALYSIS

Ii.

s.

Cl-IUPc’G’

I.>epartrmnt (Ibxivcd

AND

F.

of ChernisIry, June 5th.

E.

AMOUNTS NEUTRON

OF OSMIUM ACTIVATION

131SAhlISI-I

llnivwsify

of T ormrfo,

Toronto

5, O~~lrcrio (Cnmdn)

1968)

Expcrimcntal procedures which allow the quantitative distillation of microgram amounts of osmium and ruthenium have already been rcportcdl. ‘The procedures have been applied in this work for the direct determination of these two metals in sulphide ores. The proportions of total platinum metals in the type of arcs examined are of tlie order of nanograms/ounce of arc. -i-hedirect determination of the two metals in such saniplcs, without preconccntration, has not been accomplished by conventional methods. In recent years, the neutron activation tcchniquc, with clistillation”~3 or anion eschangc? as a mehns of separation, has been applied for the dctcrminntion of osmium and ruthenium in terrestrial sources. However, with ore samples, the analytical approaches were lengthy, requiring about 20 h for duplicate determinations:3 and, furthermore, the separation of osmium and ruthenium by distillation was not confirmccl by aclcquate data. The present work has shown that osmium is easily lost by volatilization durmg evaporation. A simple radiochemical method was devised to prevent this loss. Tnactive carrier was adcled during the distillation process but no chemical yield detcrmination was required. The overall processing time for the determination of the two metals was about 3 11. NUCLEAR

I>ATA

The nuclear data pertinent

to the present work are shown in Table

16-v.

EXPEIII3IENTAL

A scintillation counter (Nuclear Chicago Model 8725 Analyzer/Scaler) was used with a single-channel analyzer. The detector used was a 2 x 2 in NaI (Tl) well-type crystal, Model 422 type. A 4oo-channel y-ray analyzer (RIDL Model 34-27) was used in conjunction with 3 x 3 in NaI(T1) detector. Radiation measurements were also ma.de with a 22-cm3 Ge(Li) detector (provided with a x.5-cm” thick aluminum absor* Iicsecrrch l?cllow on lcavc from the Atom’ic Energy Rcscarch Institute, Seoul, Korea. Address: Department of Chemistry, University of Arizona, Tucson, Arizona 85721. Ann!.

Cibn.

Ada,

43 (1968)

Prcscnt

357-368

I<. S.

358

PRINCIPAL

RADIONUCLIDISS

DP

OShlIUhl

Sla.!llc

/

isotope

dlllWAZ?MX

A cl ivdion cvoss-sectiorr

1%)

(I)

________---’ “Ws

solofiic

4’

OORU

---

--

.._--_.---___________

.-----

__

Ild/-lijc o/ rudiourdidc

I~ctrlirrfion (1Cb I’)

--_--...---.-.. 93.b

II) 1tn(--.q

tl

,____.

1f.C.

y’s (74)

“1 11

I.T.

16 tl

Ih:lr:O.,)

I u:,(Js

3* 11

/I- (I‘121 /k’s (C)77.-1 130)

I -+0.02

0.7ao.2

18.,j

_ _____

(LIf’)

‘“‘OS

2.88

~71111 lQ3l(ll

I.+)*to,rO

--

BEAMISH

8rt3

0.2

31.3

llhlRu

._ .-.-.

il’rrdiouuclide produced by (9t.y) rerictiou

Y’” (73-558) (tsp. 28 I, 46% 558)

5.7

103rc11

F. E.

RUTIIISNIIJhl

‘“Ws

200

-

26.4

l~Kk3

_.__.-

<

0.018

*““OS

AND

-._-----..-_---.-

------

CHUNG,

l”6Iil.l -

-

tl

39.8

cl

4.5

I1

1c.c:.

y’s

32 I, 388,

(2 16)

/k’s (220) y’s (55~010) (Csp. 498, (i lo) ---

p-(“50)

Y (726) ---

ber) in conjunction with a 4oo-channel analyzer. Sartorius Ml-‘l< 5/z Microbalance. Distilled water and distillation apparatus were described prcviouslyl. Reagents Hydrogen peroxide (3099, sulphuric acid, sodium peroxide, and sodium bromate were AR.-grade reagents. The carrier solutions for osmium and ruthenium were prepared by fusing, in a nickel crucible, 50 mg of finely divided osmium or ruthenium sponge with sodium peroxide as described below. The cold melt was diluted to about 50 ml with dilute sulphuric acid (cu. 5 N) (I mg of each metal/ml). Iodine-x3x was supplied from the Ames Co., Miles Laboratories Inc., Elkhart, Indiana, U.S.A. Iron sulphate (A.R.) was dissolved in water with a minimum amount of sulphuric acid (IO mg of iron/ml). Sam$Zing

About IOO pounds of sulphide ore, collected from several Canadian Mining Companies, were pulverized to x00-200 mesh. Each sample was split by handriffling and two of the portions were accepted if their weights differed by less than 1%; otherwise, the portions were recombined and the process repeated. The sample weights were reduced to about IO g by continued sub-division. When coarse granules were found, the sample was ground in an agate mortar, as during the preliminary distillations any small amount of undissolved ores was usually associated with low recovery of osmium and ruthenium. Slamlard and tracer solutions of osmiztm and r&cnizcnt The two metals were each purified as previously reportedl. Their radiochemical purity was confirmed by y-ray spectrometry. About I mg of purified sponge of each metal was added to quartz vials and weighed. After irradiation, they were treated by the method described below. The tracer and standard solutions were Gnat.

Chitn.

Ada,

43

(rgG8)

357-3G8

N.A.A.

OF

SULPHIDE

ORES

FOR

OS AND

359

Rll

diluted to IOO ml with cu. 5 N sulphuric acid. The appropriate aliquot was diluted to ml in a volumetric flask, and the activity was measured. This was also used as a tracer solution for the distillation of both metals. As shown in Fig. I, the osmium tracer solution showed the y-peaks of osmium-xgr (half-life 16 d) at 45 and 130 keV, and also that of osmium-185 (half-life 94 d) at G4G and 875 keV. The ruthenium tracer solution showed the y-peaks of ruthenium-xog (half-life 40 d) at 498 and Grg keV.

25

875

L

__L____‘__--l._

ii . .._.

--Pulse ~6. I. y-Spectra Os;(-.-.-.-)

i

L_-._L__._.1--1.--l-.“_

of

!\ _

I

~L_._1--_-1__.._2._

height

standnrclsolutions Ru

/

+

OS.

of

osmium and ruthenium. (---

--_) Ru;

(

1

The,activities of the sample solution, distillate and standard solution, were measured by y-scintillation counting after the solution had been diluted with water to 25 ml in a volumetric flask. The flask was placed directly on the scintillation counter and the countings were continued until at least x04 counts were collected, in order to obtain good counting statistics. The radiochemical purity of the sample solution was confirmed with the multichannel analyzer. Irradiation About IOO mg of sulphide ore and ca. I mg of standard osmium and ruthenium were accurately weighed and added to tared quartz vials. Each set of ore samples, together with one standard of osmium and ruthenium, was placed in an aluminum capsule and irradiated for 4-5 days at a neutron flux of approximately 5 *x01” A-al.

Chim. Acta, 43 (IgG8) 357-368

360

I<. S. CHUNG,

F. E. DEAMISH

cm” set in the McMaster University Iicuctor, Hamilton, Ontario, Canada. In the cast of ore samples, the irradiated materials were proccsscd after a cooling period of about 4-5 clays. n

After irradiation, tlic quartz vials were opcncd in a glove box and tlic contents were transfcrrcd to tlic tared crucible by gentle tapping. ‘I;0 cliniinatc the possibility of loss, tile irradiated mntcrials were rc-wcigliccl. Sodium peroxide (ca. x.5 g) was aclded and the sample and tlic flux wcrc niisccl thorougllly wit11 a thin glass rod. ‘I‘lic moist material aclllered to tllc glass rod and was cnrcfully scraped off with anotlier glass rod. Mixing tile arc with tllc fusion flux was aclvisablc for complete dccomposition of arc. ‘I’lic crucible was covcrcd with a licl and the low tcmpcrature flame of ;L Meker burner was appliccl for about 2 min until tile misturc just mcltecl. Tile lieat was gradually r&ccl, using a mcclium flame, for about a further 3 min wlicn tlic bottom of the nickel crucible bccamc a clull reel colour. At this stage, the melt usually rcachcd a quiet fusion and tlic resulting inoltcn mass appcarecl homogenous. If tlic fusion was carried out wit11 the full flnmc of a Meker burner, the resulting melt was difficult to dissolve. T11c molten mass was cooled by rotating the crucible so that the mass soliclificcl in a layer on the wall. About IO ml of water WZLS carefully nclded through a dropper to clisintcgratc the melt, the crucible being covcrecl with a lid to avoid tllc loss by spurting. By repeating this procedure with tile total 20 ml of water, the disintegrated melt was transferred to the distillation flask. During this manipulation, tllc crucible ant1 the flask w_ere cooled in an ice bath to avoid any loss of osmium by the heat of clecompbsition. Th slight residue remaining in the crucible was clissolvecl by gently warming the crucible on a water bath for about I min with a minimum amount of sulphuric acid. Tile washings of the crucible were added to the flask. After this treatment, the activity from irradiated materials remaining in the crucible was found to be negligible.

Tllc black slurry was clissolvccl by 40 ml of sulphuric acicl (I : 2). Hydrogen peroside (20 ml) was adclccl and a slow air current was clrawn through the distillation apparatus. The flask was electrically heated for IO-IS min. When the temperature of the flask rcachecl75-So”, about 30 ml of hyclrogen peroxide (3oTL) were added clropwise to the flask during the remainder of the distillation. At this stage, the temperature usually rose quickly to about IO~O, at which temperature the distillation was maintained for 40 min. The heating was discontinued and an air current was drawn through for a further IO min. The distillate absorbed in the two receivers, each containing 5 ml of 9 N sodium hydroxide, was diluted to 25 ml in a volumetric flask. The activities of the distillate were measured with a scintillation counter by comparison with the standard solution prepared above. Each absorbing tube was refilled with 5 ml of CJAr sodium hydroside, and the ruthenium was distilled as follows: about 5 ml each of sodium bromate (20O/~o) and concentrated sulphuric acid were added to the flask and the air current was again drawn through the apparatus. The distillation flask was carefully heated to avoid the violent evolution of bromine and the temperature was gradually raised to about 100~. For the rem‘ainder of the distillation, 15 ml of sodium bromate (200/o) was added dropwise. The distillation was continued for I h and the distillate was then diluted to 25 ml in a volumetric flask. Aural. Cl&,a. Acta, 43 (1968) 357-368

N.&A.

OF SULPHIDE

ORES

FOR

OS

AND

RU

361

RESUL-I3

Sefiaratiolt of osmimt a,& mtlrenizrm by distillatio7t ‘I’he above distillation was applied to synthetic mixtures of osmium and ruthcniurn (Table II). The mutual separation of these two elements was confirmed by csamining the y-spectra of both distillates with the y-ray multichannel analyzer. All of the activity of both distillates was always collected in the first receiver. ‘PARLE

II.

SEPARATIOS (No

OF

.*Irww,rC’c‘ritZrd f/4?) _- - .

OShllUhl

,\ND

RUTIIDNIUM

RY

DISTILLATION

cxrricr ;~tlclcrl; the tlurxtion of the distillation

OS -... _.

‘!,!, Dislilld

Y’r,rrp. (“C)

_._____. _ _-. ____-_. _-___ __ JtIl OS

.-_~ itu

\\‘iIS40 min for osmium ant1 Go min for ruthenium)

..__ .___.__-..__._

OS

_

Jl’rc

x04--107 10.3.- 108 I I.2 99.0 99.6 104-107 102-107 too.3 11.2 99.4 3. 5 __..._.___... ._ ._. . ._--_-_-.____ _......._._.-. . ._- ._...._ _- _.. _-_.-----._--I_.-

3.5

*rmr.rc

111

DISTILLATION

OF

OSMIUhf

AND

RUTllENIUhl

TRACERS

PROM

Tl1&

SOLUTION

OIr

SULPHIDE

ORE

(Duration of the distillation W;LS40 min for osmium an<1 60 min for ruthenium) --_._.......-.._-- _ _-..-.. ---. .-__.- ..._.- ._._-- -... _---.-.-. --..---Trnccr urldcd o/o 1)istillrd ?‘e?np. (“C) Ore Cro-0 n) -..-- -.----. . -- --..-- --.--_

OS

Rtc

OS

It11

OS

R1c

IXstiLZation of osonizim ad rzrtlre92izcm from sohrtiovts of ore samples. In order to apply the above method to the ore samples, the two metals were distilled from the dissolved solution of sulphide ore as follows. About IOO mg each of ore from two different locations, the Sudbury ore and HCGM* ore, were decomposed and the fused mass was dissolved with sulphuric acid as described above. The solution of ore sample was added to the flask and the osmium and ruthenium tracer solutions, respectively, 3 ,ug and xrpg, were added. The distillation was carried out as described above (Table III). As shown in Table III, the dissolution procedure for the ore samples showed no retarding effect on the distillation behaviours of osmium and ruthenium under the stated conditions. In order to verify further the applicability of the distillation method to ore analysis, the mixture of osmium and ruthenium tracer was evaporated and fused together with ore samples and the distillation behaviours were examined as follows. About 0.x g of finely pulverized ore was added to the nickel crucible which was spiked with 5 ml each of osmium and ruthenium solutions, each containing about l

Hollingcr

Consolidated

Gold Mines, Ltd.,

Timmins,

Ontario,

Canado.

Anal. Chhitn. AC&, 43 (1968) 357-368

I<. S. CHUNG,

362

F. E. REAMISH

3 ~16and x1 /qg of thcsc metals, respectively. The solutions were slowly evaporated on the water bath. After dryness, x.5 g of sodium peroxide was added. The fusion, dissolution and distillation were as described above. The result showecl about 60’y0 recovery of osmium. This was rcpcated with about 71J’y0recovery of osmium. Osmium was shown to be lost during evaporation, as follows: the same amount of osmium and ruthenium tracer solution were aclclecl to a rg-ml beaker and cvaporatcd slowly on the water bath. Almost no activity rcmainecl in the bealcer after evaporation. It has been reported’ tliat the aclclition of iron(I1) sulphate or chloride stops loss of osmium by volatilization, but in the present worl< losses wcrc found even after the addition of iron(I1) sulphate (Table IV). In contrast to osmium, IOO”(~ retention of ruthenium was always obtained. TABLE I.OSS

IV

OF

OShllUhl

HY

ISVAl’OI
IN

Imr,rcflirrfcIy

1’1115 cl&r*

_------.--20

ttrg

of

ivotr(1

I)

l’l<15SlZNCI5

OIC

24 .--_---

H

IRON

SIJI.PIIATli”

ape,

I?cnrdrs --__

#wsctrt

0.r activity acklccl OS activity rccovcrccl Rccovcry ((XI)

12.7.18 11,233 88.1

50 ,1&gof irorr(lI) prcmrt 0s activity nclclccl OS activity rccovcrccl Rccovcry (“/“)

11.777 97.5

12,077

12,403 I I,c)4I 96.3

12,436 I 1,836 95.2

12,754 I2,o43 9.t.4

I2G.537 I2Gtg 11,925 11,945 95.1 9-t.4

12,329 11.88G gfi.4

12.070 11,150 92.5

12,113 11,649 gG.2

Ix408 Iz.ofiI 97.2

a0 rtrg of irouf II) ~p~escnt 20,7rg Ru activity atlclctl 20,998 Ru activity rccovcrctl 21,18G 20.816 Rccovcry oA 100.9 100.5

20,GGg 20,831 100.8

12.287 I I,78g 95.5,

l’hc

osmium trnccr solution was cvnporntccl in tlic prcsencc of 20 mg of 1:cz+

The osmium tracer solution was evnporntccl in the prcscncc of 50 mg of PC=+ The ruthenium tracer solution was cvaporntccl in the prcscncc of 20 mg ol Pc~~

a The osmium nncl riithcniuin trnccr containctl 3.5 /cg ant1 I I.2 116 of the rcspcctivc metals. The tracer solution (cnch 5 ml) and iron sulphnte solution wcrc nddccl to ;L x5-ml bcakcr and cvnporatccl slowly on the wntcr bath. After clryncss, the rcsicluc was dissolved with clilutc sulphuric ncicl nncl clilutccl to 25 ml in a volumetric floslc. The activity was compnrccl with the rcfcrcncc standard.

As shown in Table IV, ~-12% of osmium was always lost during evaporation and there was no improvement on ageing the solution by allowing to stand overnight.* The loss of osmium by volatilization was prevented by an iron(III) hydroxide precipitate formed by the addition of sodium hydroxide to the tracer solution as described below (Table V). The distillation of osmium and ruthenium tracer was then carried out as described above except that iron(II1) hydroxide was precipitated (Table VI). The low recovery of osmium by distillation, 60% and 78’j/,, seems to be due to the volatilization of osmium rather than to any peculiar distillation characteristics. * It is known thrrt during agcing, the complex. [Ru(I-I~O)Cl~]*-, uncler6ocs gradual hydration volving progressive rcplnccmcnt of the Cl- group of the complex by an quo-groups. Awl.

Chim.

A&z,

43 (rgG8) 357-368

in-

N.A.A.

OF

R15TKNTZO.N

SULI’HIDE

OF

----.--

ORES

OShlIUhl

--...-___

141’

-_-_.-

FOR

0s

IRON(iII)

sbxovcr

ntltlcd rccovcrcd

HYT)RO.XIDE

01’

procedure

TKhCER

P-ROM

IWSISD

_ _.,..__

2 3

_._.

ACTIVATION

.

AXAI.YSIS

____--__-___

EsfJl

.

OF

~._____ AI

A3 A7 A8

Ag

_

__. _. ,--..

___. .

Sttlpltide

.._..._ _._._

I-ICGM

..

OShlIUM

._

AND

IVeigltf of sample

_

.

--_..

98.6

...-..--

_.

RUT~IENIUM

.

IN

__.. ..--

SULI’IIIDE

ORE

(IN

THE ABSRNCE

OF

CARRIRR).

--

.-.-_

OS

fottrrd

7;.

Rtc fouud

Rtr

(w)

(P.P.r,r.)

_---_-.

5.9

0.05

-

-

3.6

0.02

IO

0.07

0.8

0.01

-

-

184.40 I G4.90

8.5 11.8

0.05 0.07

36

0.2

20

0.1

106.27

X4.0

0.13

58

200’

rzg.16

zoo’

I

lcvcl I-ICGJI z ,000 lcvcl Sudbury arc Sudbury conccntratc Sudbury concentrate

_.

(Yb)

pmt.) (W) fwf?:) . ~_.----_-__.-..-____. -- _.._..... .- _._.. - ._..._-__. .-_.._. --..

I-ICGRI Icvcl

08.5)

_____

99,2 98.2

ro.orR

..

-.-. ._

ORE

Recovery

9.997 1 o,oc#i

________.______

OYC

A2

__.

10,083 10,280 ro.rC,z

I

100.1 -

-_- __._-___-.____-.

OS rczovcred (ncf ivity)

OS added

_... -_.

SULPIIIDlS

-___-.

(3.5 I’d (rtcf ivily)

__---_._.

20.794 20.730

is tlcscribctl below.

----__---.~_------._-..---.~-.--

IXstillatiora uo.

-_--.--

pe)

20.976 20.993

20,g.+z

99,O .-._--

. -._--.-__--___-

frr.z

21,087 100.7

1o*.tg5

100.7

___.

OS~IIIJI)l

IO.(iOI

10,805

99.8 _ -________-____

DISTILLATION

EVAPORATIONS

Rtrlltrnitt~rt ._.-.. .-_. -..-_-_-.--._---____

10,727

I o,g28

precipitation

n The

DURING

I’RltCSPITAT1ON

(5 116)

10,gw

y “/:,

___________.

363

.._ -._-

Ostftittnt

Activity Activity

Ru

AND

52.82

127.50

* A small amount of ruthenium and 1311 contamination wcrc noticcd The resulting small error was not considered in the above results.

-

0.5

in the osmium

distillate.

Activation analysis of osmiunt and ruthenium in szrlphide ores (in the absence of a carrier) A trial analysis by neutron activation was carried out for the determination of the two metals in sulphide ores. Six samples from different locations were analyzed (Table VII). As shown in Fig. 2, the osmium distillate from the above determinations was contaminated with ruthenium and iodine-131 activity. The amount of ruthenium contamination was estimated roughly by y-ray multichannel analyzer to be in the range 10-40 ng of ruthenium. The distillate of ruthenium was, however, always found to be radiochemically pure. It was interesting to notice in this experiment that iodine131 was also present in the osmium distillate. The identity of iodine-131 was confirmed A#al.

Clkrn. Acta,

43 (xgG8) 357-368

I<. S.

364

CHUNG,

P. E.

BEAMISH

by comparing its y-spectrum with of tlic standard iodine-13r obtained from the Ames Co. While the concentrates of sulphidc ores from Suclbury, Ontario showed the prcsconceof l:JlI activity, tile latter was absent form tllc HCGM sample. Iodine-rgr seemed to bc radiogenically procluced from tellurium prcscnt in the arc by the reaction, l:JOTe (n, y)

131’rc

P--_t

l3tI

.

It was possible that the coclistillntion of ruthenium low amounts of these two metals in the ore. Therefore, carried out with tile adclition of carrier.

L----L__1

--L---L_

was due to the cxtrcmely furtllcr experiments were

-1

Pulse height-e ITis. 2. y-Spectrum of an osmium distillntc from Suclbury sulphitlc arc (with osmium and iodine contnmination). 5-h data nccumulation with a 3 x 3 in scintilhtor x0 clays after tllc end of irmdiation of tlic arc.

To a 30-1171 nickel crucible, 0.5 mg each of the carrier and Go ng of active osmium tracer and IIO ng of ruthenium tracer were added. After the addition of IOO mg of sulphide ore and 20 mg of iron as iron(I1) sulphate, the iron was precipitated as iron(III) hydrosicle by the clropwise addition of 2 ml of ca. 1.3 M sodium hydroxide solution. The solution was carefully evaporated on a water bath and the residue fused with sodium peroxide. The distillation results are shown in Table VII. Activation analysis of oswti~~~rt altd rzrtlteuiwn in the HCGM sulfiAide ores (in the prese3tce of carrier) As shown in Table VIII, the separation of nanogram amounts of ruthenium Am&

Chim

Ada,

43 (x968) 357-368

EXTRACTION TABLE

AND

DETERZIIXATIOS

OF

Sn,

As

ASD

365

Ge

v

DETERMINATION

OF

GEKhIANIUXT

IN

ShIJSLTISG

DUSTS

_--

Snrlrplc 11 -A

Take #a (g)

G~vwnniton

0.113

0.038

0.326

o-037 o-037

I3

O.OIOO” 0.020V’

0.503. 0.490,

C ---

0.500

0.205

.---

fottnd ----~

(‘x)ll

0.495 0.493

0.0058,0.0056 .--.. -...----

__.--__. .._

R Constituents:

A: Cu 33, P’b ‘f, %n 3. As 0.3, SC 0.2%,. 30, Pb 15. %n IO, I\S 0.5, SC 0.005’%,. 13: cu C: Cd 55, %n 4, As 0.22, SC 0.01~~. 13 0.50, b Germanium prcscnt (ph~nylflrroronc r71cthotl) : h 0.038, 0 An diquot of snmplc solution W;LS t:Lkcn.

C

0.0058~/~.

in absorbance occurred, Therefore, half the extract of germanium(N) chloride was transferred to another separatory funnel, so that the conversion could be made without interference from hydrochloric acid. The absorptivity for germanium at 360 nm thus obtained aSreed well with that already given in Table I. Arsenic(II1) chloride could be removed completely from the first extract by washing with potassium bromate solution. Selenium(IV) is extracted by benzene 23.24 to a small extent from hydrochloric acid. The element was found to be extracted into cyclohexane also in the first extraction and to cause a positive error. Therefore, selenium(IV) was removed from the first extract by washing with IO M hydrochloric acid. A simple spectrophotometric method for the determination of tin, arsenic and germanium has been presented. PAUL AND GLBSON”~ have developed a method for determining tin in tin-rich metals and alloys, which involves iodocthane extraction of tin(IV) from a solution 06 M in hydrochloric acid and 4 M in potassium iodide, and the measurement of the extract at 410 -430 nm. Their method requires stricter control of the composition of the aqueous phase and in removal of co-extracted free iodine and tin(IV) is not quantitatively extracted. The method presented here is simple and selective, and useful for the cletermination of tin, arsenic and germanium in various samples. SUMMARY

Tin(IV). arsenic(iI1) and GermaniumfIV) can be extracted quantitatively into cyclohexane from solutions containing sulfuric acid and sodium iodide. The extracted iodides have characteristic absorbance spectra in the ultraviolet region. When the measurements are made at 364 nm for tin, at 282 nm for arsenic and at 360 nm for germanium, the respective absorption maxima, the calibration graphs are linear and the molar absorptivities are S700, g7oo and 6600, respectively. Arsenic(TI1) can be extracted mainly as its iodide from hydrochloric acid solutions containing sodium iodide, the molar absorptivity at zSz nm being also 9700. Recommended procedures are given for the determination of tin in juice, tin an.d arsenic in steels (simultaneously), ancl germanium in its concentrates. Axal.

Chiwt. Ada,

48 (1969)

357-3G6

K. S. CHUNG,

366

F. E. BEAMISH

* While the osmium results are to MoIGAN's results (standard deviation of 2050%). reasonably close to each other, the ruthenium results show a coefficient of variation of GgO,!).However, with the exception of result no. 2, the precision of ruthenium analysis is similar to that of tlic osmium dctcrmination. In view of tlic possible effect of neutron self-slliclding~t, is was originally intcndccl to irradiate the submicrogram amount of the standard as suggested by HosTI.:~, the small amount of osmium solution on MOICC;AS~~ and Mortnrsl” who evaporated filter paper’ or Spccpurc silica 4. This idea was abandoned bccausc of the osmium loss obscrvccl in tile present work. Moreover, when Whatman paper No. I, spotted with osmium solution and wrapped in Mylar paper’, was irradiated in the reactor for 4 days, both the filter and Mylar paper were so easily crumbled tllat it was clifficult to transfer cluantitativcly from the quartz vial. As stated above, the rutlicnium contamination in the osmium distillate was very small, 1:.c. in tlic range o.s-x.5 ng (Table VII). l’hc prcscnce of ruthenium contamination was confirmed only by the simultaneous counting of the combined osmium distillates. The above clata for ruthenium contamination were estimated roughly from the photopcak area of the 4#3-keV peak of r03Ru compared with that of known amounts of standards after counting for IO h by multichannel analyzer. Tlrc effect of 1arI activity on the determination of osmium was similarly evaluatccl, and found to be very small. I-Iowever, the sample containing the 1311activity was avoiclecl in this work l~ccausc it was primarily intended to examine the applicability of the distillation

r_,L.._1._,-_L____

40

..__ ___

80

120

160

._...L______

.,_

200

__

_-

.-

. ..I

--.

240

1_____.-

..L.._..

280

Channel

number

Fig. 3. y-Spectra of rcsiduc in the flask nftcr clistillation of osmium and ruthenium from sulphidc arc (Sudbury arc, Ontario, Cannda). Spcctrurn I : zo-min data accumulation using a 22 cm3 Gc(Li)data accumulation using 3 x 3 in dctcctor, 12 days after 5 days irradiation. Spectrum 2 : xoo-rnin sodium iodide scintillator. (The numbers in pnrenthcscs correspond to the exact chnnncl number.)

+ This was taken by the present author as the coefficient Aw~l. Cirinr. Ada,

43 (1968) 357-368

of variation.

N.A.A. OF SULPIXIDE ORES FOR

OS

ANI)

Ru

367

method as the separation procedure in the submicrogram range. Throughout the experiments, all the activity of the distillate was always collected in the first receiver. At the beginning of the expcrimcnts, difficulty was encountered in distilling the last trace of osmium from ruthenium 11. To rectify this, several distillations were carried out with the addition of potassium permanganate” to decompose hydrogen peroxide before the ruthenium distillation. Although this treatment gave a satisfactory removal of osmium, the permanganate treatment was abandoned when it was founcl that careful manipulation of the distillation proceclurc effected satisfactory separation of osmium (Tables III, VI, VIII and IX). In the present work, the determination of chemical yield was purposely avoiclecl althougli the addition of carrier was found to be necessary. The reason has been pointed out in a rcviewl” in which the inadequacy of the currently used proccclurcs for the yield determination was emphasized. It has been reported7 and was also indicated by the y-spectra of irradiatecl samples after distillation (I?@. 3), that platinum, iridium, pallaclium and rhodium are not distilled by this method. The possible interferences relevant to the present work in the neutron activation are as follows”eia: loaIr (n, p)la3Os, iW?t(n, a)iOaOs, lolIr (n, p)lOiOs, ~OHPcl(n, bc)lOJRu and za%J (n, f)i”sRu. However, the irradiations were made in a predominantly thermal flux, where the cross-sections for these reactions were generally quite low compared to the (n, y) activation cross-section. Therefore, it was unlikely that these interfering reactions were sources of error. It is a pleasure to acknowledge indebtedness to Dr. Ii. E. JERVIS and his group at the Department of Chemical Engineering and Applied Chemistry, University of Toronto, for the use of their counting equipment. SUMMARY A neutron activation method; involving a radiochemical separation based upon two consecutive distillations, is described for the direct determination of nanogram amounts of osmium and ruthenium in selected sulphide ores. A loss of osmium due to volatilization occurred when the tracer solution was evaporated. A simple radiochemical method using iron(II1) hydroxide precipitation was devised to prevent this loss. The proposed method was applied to ores expected to contain only traces of platinum metals. The addition of the active carrier was found to improve the separation of these two metals in the submicrogram range, although, no chemical yield determination was necessary. RI%UMf? On decrit une methode par activation aux neutrons, comprenant une separation radiochimique basCe sur deux distillations consecutives, pour le dosage de teneurs en osmium et en ruthenium, de l’ordre du nanogramme, dans des minerais sulfur&. 11peut se produire une perte en osmium par volatilisation; en peut l’eviter en utilisant une simple methode radiochimique par precipitation d’hydroxyde de fer(II1). Ce procede est applique B des minerais ne renfermant que des traces de metaux du platine. L’addition d’un entraineur permet d’ameliorer la separation. Anal. Chim. Ada,

43 (1968) 357-368

368

K.

S. CHUNG,

F.

I;.

SEAbfISH

1% wircl clie direkte Bestimmung von Submikrogrammen Osmium uncl Ruthcnium in sulficlischcn Erzcn mitt& dcr Neutroncnaktivierungsanalysc heschrieben. %ur direkten Restimmung von Nanogrammen wird cinc racliochemischc Abtrennung clurch zweifache Destillation clurchgcfiihrt. 13cim Eindampfcn der L6sungen tritt tin Verlust von Osmium tlurch Vcrdnmpfung auf. Durch Ausfiillen von Eisen(III)Ilyclroxicl wit-cl clicser Verlust vcrmiedcn. Die vorgeschlagene Methode wurcle nur fiir Erzc mit Spurcn von I-‘latinmctallcn verwendct. Durch %ugabc eines aktiven Triigcrs wurde die Trcnnung vcrbesscrt.