Separation of Antimonic Chloride from Antimonous Chloride by Extraction into Isopropyl Ether FKAKK C. EDW'4KDS 4ND .ADOLF F. VOIGT Iowa State College, Imes, Iou*a The distribution of pentavalent a d trivalent antinion, between h?drochloric acid solutions and isopropyl ether has been studied for tarious concentrations of arid and antimony. An extremely rapid equilibrium results in a quantitatibe extraction of pentavalent antimonj over the acid range 6.5 to 8.5 .Mwith a pseudodistribution coefficient greater than 200. The distribution coefficient for the extraction of triFalent antimony is 0.016. A procedure using two distributions will quantitati\elF and rapid]? separate pentavalent and trivalent antimonj.
T
( 4 ) . Standardization of the pentavalent antimony solutions arid
HE prdereritial extraction of antimonic ovcr antimonous chloride by ethyl ether from hydrochloric acid solutions was reported i n 1911 by Slylius and Huttner (S), whose studies w r v made over the acid range 5 t o 20% (1 to 6 X). Uiider their most favorable conditions 85% of pentavalent antimony and 6y0 of trivalent antiniony were extracted into the organic layer, as shown in Figure 1. Because of the int:fficicncy of the separation and thc. critical acid concentration required, thtlir mtkthod h usti as a mcmis of separation of the two valencts statrbs of antimony. For the similar ext,raction of ferric chloride iron1 hydrochloric acid solutions isopropyl ether has been shown (by Ihdson, Forney, and Swift, 1) to possess certain advantages ovvr cxthyl ether. Consequently isopropyl ether has been studied as an oxt ,,actant for the separation of antimonous and antimonic, chlorides. Thr. range of acid concentrations studied was cstendcd beyond those covered by Mylius and Huttner. The use of isopropyl ether proved to give a rapid and very efficient separation of trivalent and pentavalent antimony over a wick rangc of hydroc*lilwic acid concentrations.
subsequent analyses for pentavalent antimony were made by the potassium iodide method ( 2 ) . Standard solutions required in the Ynalytical procedures were prepared by conventional methods. All the hydrochloric arid solutions of the antimony chlorides i v c w 8 nil. in volumr. In the extraction studies on solutions
z 0 t-
0
a
a + X w IZ w
0 EXPERIJIENTAL METHOD
a W a
1)istributiuri data were obtained o n three types of hydrochloric acid solutions of the antimony chlorides. One type of solution contained only trivale,nt antimony, a second only pentavalent antiniony, anti the third contained equimolar mixtures of thv two. In t h r studits reported herc, tht, extraction was not tried over a range of small to large, va1uc.s of the ratio of trivalent to pentavalent antimony.
HCI M Figure 1. Extraction of Pentavalent and Trivalent .Aiitiniony- from Hydrochloric Acid Solutions, Using Ether Ex tractants 1. 2.
I n one experinleiit one of thew solutions \vas placcd in :t sepamtorv funnel and isopropyl ether, saturated with hydrochloric acid 111.6 .TI), was added. The extraction was carried out t)), shaking the aqueous and organic phases for 5 minutes a t room temptmture. The separatory funnel was then allowed to stand until thr. two layers separated and the lower aqueous layer \vas drawn off, This aqueous layer \vas analyzed for. either trivalent or pentavalent, antimony. From the amount of trivalent or penta\ d e n t antimony found remaining in the aqueous layer the amount vstracted into the organic layer was calculated. For those solutions initially equimolar in trivalent and pentavalent antimony, duplicate extractions under identical conditions were t)hen carried out in order t o determine the amount of the othpr valence form c.str:1cted.
3. 4.
Extraction of S b - ' - - - and Sb'-- using ethyl ether (3) Extraction of S b - - ? - + from solutions containing only S b ' + - - - using isopropyl ether Extraction of Sb+-&+' f rom solutions containing equimolar amounts of Sb and Sb 7 using isopropyl ether Extraction of S b - - - from solutions containing only S b - - or equimolar amounts of S b + - - and S b - - - - - using isopropyl ether
--
+
+
+
7
equiiiiol;ii, i n ti,ivalent and pentavalent antimony, for rxaniple, thc
EXPERIMENT.&L
The isopropyl ether used had a boiling range of less than 2' and gave a negative test for peroxide. Various solutions of antiiiionous and antimonic chloride were prepared using c . ~ crystal. line antimonous chloride and reagent grade antimonic chloride. standardization of the trivalent solutions and all analyses foi~ triv:ilPnt antimony viere made using sulfatoceric arid ns oxidant
solutions tvere prepared by pipetting 1 ml. of t,he pentavalent stock solution and 1 ml. of the trivalent stock solution into a 50nil. separatory funnel. These stock solutions contained 60 mg. ml. of ant.imony dissolved in 11.6 .I1 hydrochloric acid. .Idditions of 11.6 Jf acid and water were then made using semimicroburets to bring thi! initial concentration in hydrochloric acid to the desired value. The resulting solutions were thus 0.0625 -I1in each form of antimony. The initial acid concentration was calculated by assuming t,he 2 ml. of antimony stock solutions to be equivalent to 2 ml. of 11.6 J1 acid. The acid concentrations of the solutions containing antimony are purely fprmal rather than niolnr concentrations, as there is undoubted association of t,he :intiinon!. Lrnd :wid i n the aqueous phase. Although t,his is recog-
1204
V O L U M E 21, NO. 10, O C T O B E R 1 9 4 9
1205
Table I. Distribution of Penta\alent and Trivalent 4ntimonJ between H J drochloric 4cid Solutions and Isopropj 1 Ether" IIllrlal I I ( I ('on< rntidtinri
.Ilolf'v
17fpi
2 ,0 2.9 2 . !3 4.35 4.35 4.33 .i8 ,i8 R .!46 6.96 8.0 8.0 8 0 !1 0
1 mal \ oliinie of i c i u r o ~ ~1. a I < 11I
17Ytla
