YOTES
April, 1960 method of h i s t q u n r c s to rqiintions P = ad - h , where a and h were constants, rl th(A drrisity in g./ml. and P wts the \\right per writ . of glj two1 defined by wt. of glycerol 100 P = wt,. of glycerol + F t . of water T A stock solution of 0.8 M hydrochloric acid was prepared by dilution of the analytical reagent. An accurate value of its concentration mas obtained from conductance measurements using the d a t a of Owen and Swecton7and Shedlovsky The standirdizcd glycerol stock solutions were suitably diluted with either water or the 0.8 .TI acid t o obtain the solutions whirh were used in the conductance measurements. These dilutions and the conductance measurements are most readily desrrihed by considering a n actual case, say 10% glycerol: P a r t of a glycerol stock solution was diluted with water to prepare a water-glycerol solution of P = 10. Another portion of the same stock solution was diluted with the 0 8 J/ acid to give a water-glycerol-acid solution also of I' = 10 (it should he noted t h a t for these ternary solutions P is not the weight per cent. of glycerol in the total solution, but only of the n-atrr-glycerol part). This solution was surccssively diliited Tvith the binary solution of the same P value t o enal)le the conductance measurements t o cover the range 0.008-0.1 J I acid concentration a t P = 10. This process of preparing binary and ternary solutions having the sbme P values and using the binary t o dilute the ternary solution was repeated a t least twice for each of the three concentrations P = 5 , 10, and 20, respectively. 1\11 weighings wilre referred t o vacuum. T h e 5 , 10 and 20y0 n ater-glycerol solutions had densities and viscosities agreeing t o 0.059 or better with the literature values,6 and had specific condiirtances of about 2 X 10-6 ohm-' em.-*. To find the molaritv of the acid in the glycerol-acid-water solutions the diffewnce in dcnsity between the binary and ternary solutions a t the same value of P had t o be known and was assumed t o bc n linear function of the arid concrntr'ttion expressed :IS rrt. percentage = 3%.of HCl X 100 n-t. of HC1 wt. of glycerol wt. of water For this purpose the increase in density caused by 1% of hydrochloric acid was taken as 0.00403 g./ml. a t 25'. T h e conductance measurements were made in an oil thrrmostat a t 25 + 0.002' in the u s u d manner3,' and t h e rcsistnnces extrapolated t o infinite frequency. The values of the eqiiivalcnt conductances a t each glycerol concentration were extrapolated t o zero acid concentration by the method of Robinson and stoke^.^ Vse of the d parameter for hydrochloric arid in mater10 gave a satisfactory cstrapolation in a11 the glyrerol solutions.
+
+
Results The limiting equivalent conductances of hydrochloric acid ,io and of hydrogen ion A 0 in the three glycerol solutions are given jn Table I. Transference numbers, obtained from the literature,j were used to calculate the limiting ionic conduct'ances. The maximum experimental error in 110 is estimated as 0.08%. The relative fluidity qo,/q is given for each solution; the value of g is that measured h u e , and go is taken as 0.893 cent'ipoise.
Discussion The remarks made by previous au thors4JSl1regarding conductance measurements for hydrochloric acid in sucrose and mannitol solutions a t 25' seem ( 7 ) B. n. O n r n 2nd F. H. S w e t o n . J . Am. Chcm. Soc.. 63, 2811 (1!21l).
( 8 ) T. Shedlovsky, ibid., 54, 1411 11932). ( 9 ) Robinson and Stokps, "Electrolyte Solutions," Butterworth, Sci. Pii'd.. London, ILngland, 1%5, p. 150. ( I O ) Ref. 9. p. 148. (11) I n ref. 1,Table 1, t h e entries obtained b y this author for hydrochloric acid in 207, sucrose should read A' = 287.4, R = 0.674; and in Table I V of reference 5 t h e values for hydrogen ion in 20% sucrose 239.2 and R = 0.884. should read X o =i
50 1
TABLE I IJMITIXG EQUIVALENT CONDT S C E OF -4CIU" A S D HYDRWESI O N u b I N 5, 10 A N D SOLUTIONS A T 2.5' 5%
10%
~~YDROC'111,I)RIC
L'o'L
C;LYCEROI.
20%
388.9 353.3 283.9 R 0.912 0,829 0,666 A0 319,3 290.2 234.0 r 0.913 0,830 0.669 va/v 0.884 0,774 0.57'3 a )io in cm.2 ( I n t . ohm)-' g. rquiv.-'; R = ,io (in glycerol solution)/ho (in wttpr). *'Ao in r m . 2 ( I n t . ohm)-' g. equiv.-'; r = A0 (in glyrerol solution)/ko (in water). 120
t'o apply also t o glycerol. As before hydrogen ion is t'he least aff ected of the univalent, ions by the solution viscosity, and its mobility lies closer to the Walden's rule value than to it's value in pure water.j The viscosity of t,he glycerol solutions appears to be somewhat more effective than t,hat of siicrose or mannitol solutions in retarding hydrogen ion. This has been interpreted for other ions5 as due t o the hydrat'ion characteristics of either the glycerol molecules or the ion being considered.
EXCHAKGE OF RADIOCHLORINE B E T K E E K MOLECI'LAR CHLORIKE ASD CARBOS TETRACHLORIDE BYIRVING M. PEARSON A N D CLIFFORD S. GARNER DepaTtment of Chemistry, Cnaierszty of California. Los A n g e l e s 24, Calzjornia Recened October SI, 1959
I n 1937 Rollefson and Libby2 reported no significant exchange ( t 1 l 2> 7 hr.) when solutions of Clz (37-min. C138label) in CCl, were exposed t o ultraviolet light for 30 min. a t room temperature (enough light absorbed to dissociate all Clz molecules present four times). Later Downs3 found no appreciable exchange in a solution of ClZ (310,000yr. C136label) in CC1, kept in the dark for one week a t room temperature (single experiment). Recently Schulte4 reported significant C12-CCl, exchange (C1'6 label) under the influence of Co60 y rays, ultraviolet, sunlight, and even in the dark a t room temperature. His samples were contaminated with relatively large percentages of HC1 and presumably a radioactive orgaiiochloride impurity (probably formed by attack of C1, on hydrocarbon grease in his vacuum system). Because of the limitations of the previous studies on the dark exchange and because we were interested in its effect on another exchange being studied, we have investigated the C12-CC14 exchange in the dark and in sunlight over long time intervals in systems of high relative purity and a t least 100 times more concentrated in Clz than Schulte's exchange solutions. We have shown that radioactive organochloride impurities have an appreciable effect on the apparent exchange. (1) Supported b y U.S. Atoniic Energy Commission under Contract AT(ll-1)-34 Project h-0. 12 (2) G. K Rollefson and W. F. Libby, J . Chem. Phus.. 6, 569 (1937). (3) J. J. Douns, Ph.D. Thesis, rlorlda State Unirersity, 4ug. 1951, p. 3 5 . (4) J. W Schulte. J. A m . Chem. S o c . , 79, 4643 ( 1 9 5 7 ) .
502 TABLE I C!,-ccl~ EXCI.IAXGE IN eel.: ~ O L I ~ T I OAKT 22-55' Exchsnge IllUl
I.
tini(b,
days
(PI?),.I1
Svt c . i i . n i . " in C12
Net C . I ) , I I I . " i n C'rl,: lwforc~d i b t . nit13r dist.
lOl:k,
-11
SCI'.
'
2r
10' 1 i:b
~'set..
1
2 , 8 =!= 0 . 9 0.9 i1.2 0 . 149 3200 i 40 2 . 1 f 1.1 0 ,\Ig(ClOa), d r j ing tube in inactnv CCl, to 10 ml. for clip-comtnig. St:itistic:il roiinting errors R erc Icept blow 2 7 standard dcviation. Tli A Pyres hulh on it high-vacuum system, frozen a i t h liquid N,,pumped on, and traces of HCl removed b\ suirounding risuallr very small radionctivitr from ail\ potassium halt the bulb with :t n-pentane slush-bath at -130" (vapor pres- present n as corrected for bv determining all tiarkground sur s of C1, and HC1 are ca. 0 2 and 20 mm., respectivelj ) rates, usuallv en 24-25 counts p r r minut(>[c.p ni '),on aoluand c )niiwting to an evacuated ti ip a t - 196'. The puri- tions identical in composition n ith thaw I~enigmcu~iired fied C'l, \\as Iahelcd iiy high-temper:iture c~qrulihration~mith except for the :thsenI*e of radio(-hlorinc. Coincidence. corlabelccl \gClpic,ripitittc,d from the labeled HC1 and dried and rections were 1w> than 1°C. Countinq r &te>in CC1, ner(> fused 1 1 1 I neim to remove n a t c r The labeled C ~vLa s repiiii- converted to an "nqueous" b:ws h7- iiw of :i fartor of 1.03 heti hy the above fractionation procedure, then kept frozen empiricallr drtrrmincd. The m c m i t m t l n r t i dvintion in a bulb on the high-cacuum sjstem, except a h e n being from the mean of the total c p m pt'i m c l ~01 C1- in thc f i v ~ transferr ,d, in order t o minimize attack on the high-temper- cwhange solutions n as onlv 0 8 7 . :tturr-giade Halocarbon glens(' in the stopcock and joints. Results and Discussion Carbon Tetrachloride.-- J T Baker ".4n,tl> zed" CCI, W : I ~ purificd hv the method of W d l ice and w111nrd,7cvrrpt that Seither our nieawremeiits iior thwc of earlier in the i m t d stvp t h r b:tturated solution of C1, in CCl, nac irrxliatc.81 v, ith a 10-n:itt ultrav1olct immersion source foi iiivc estah1i.h the exchaiigc ratc Ian-. one ne('&.. Thc Iiirrified CC'I, ( h p 76.8') n:ts stored in a If, in aiialogy with the Br2-CC13RrewhmgeQin the qraduatetl Pvrex h i l l ) attached to t h r high-v~icuiimsj stem. gas phase a i d in liquid CC1, wlutioii at ca. 100Other rhemirals \rere reagent grade. 220", the C12-CC14 exchange rate i q assiimed to Exchange Runs -Known amounts of labeled Clz were condensed at -196' into graduated 12-ml. Pyrex tubes (pre- be given by R = I, (Cl,) 1/!(CC14)= t b ' 'la, iimag' bc viously bahed out and cwtciiatcd) and the solid pumped on calculated from m d fracstionatcd at - 130" as described above Purified R = - [8ah/(4a 2h)tI I n (1 - f ) (1) CCla wa,c distillrd onto the C'lJ (in the dark eucept for occaF = (4a 2b)x/4ayo (2) sional hyief extminittion with a flashlight), the mixtures pumprd on a t -196", fiartionntcd at -130", cooled to where R ig the constant rnte of euchange of C1 -196" a n d the tuhes wiled off hv torch nt a constriction nhile opcsn to a high vnruiim The mixtiire- nere thaneci to atonis (active p l u ~inactive) betmen CClb and CI, room tcrnpcrnture. Onr sollition as proc8esst.d nt once as a in gram-atom< I.-' Gee.-' i n a give11 ruii. F i. the "zero-timr" s:rmple T n o othcis neic kept in the dark a t fraction e-whaiige, mid .T and go arc' the net c p.m. room tcniper,ttiirr, for 48 ant3 21 1 d:n 5 , iesliec~ively,and the of the initially iiiactive CCl, at time t and of the rcmaining t a o wcrv c ~ g o s c dfor the C1, a t zero time, respwtiwly. T7a1u3s of li giJwi in (hiring the d : w :rnd to 1:rhorntor.r~ Table I are h i e d on "after-distillatioii" I valileq. 16 hours pcr tl,rv Aftcr the iiidic~atr~cl tinic, thc (ontents of ich tiibe \ins Table I nlco give. the himolecular rntc coiistant frozen M ith liquid S j , thc tube tip broken ott and thc t u h c k b obtained from eqiiatiouq 1 and 2 tor the asinsrrted quirklv into it g s. fl t i h containing 100 nil. of 0 1 f air-frw KI, t h r flask qtopptwd and thc contents stirrcd until sumption R = kb((&)(Crl4), since if the exchange the CCI, had t1i:tard The libcrated I? w : i ~titrated mith iq not of nrdcr 3 / 2 it may well he wand order. standard S:izS,O1 to :L starch end-point. Trace amounts of Rows 6 niid 7 nf Tnhle 1 g i w Schiiltr':: reqiilts for HCl ner-. then tieterminid h> titration with standard haw. comparison F':tch nndyzed mixtiire 4 as acidified s1ightl.r n i t h HSO,, The reductinn in actility of thc C'C1, pha.e on and the phases separated for radioassay. distillation may ari2e from an orga1iochloride imDithizonr and SnCI? spot teats* made on thc "zero-time'' mixture p v e negatlve tests for Hg(1) and Hg(I1) (chlorides purity formed by reaction of C12 n ith 1Talncart)ov of 4hi.h might havc formed h y CI, reacting n i t h traces of greaee wed in the qtopcockq of tho high-vacuum Hg vapor in the high-viiriium SJ stem, and which could ronreivablv evchange n i t h CCI,); n control test showed that syqtem (wch a "grease chloride" dcliberatcly 0 4 wg of Hg(I1) could have been dctccted in the ea. 15-E. produced under more favorable enixlition< in coilexrhangrb solution. trol euperinicntq was qiixntitatir-ely left hehiiid Radioactivity Determinations .--A 10-ml. aliquot of each nheii CC14 TI^. cliitilled off of wlutionq of the
+
+
(1
( 5 ) J . ,J, Downs and It. E. Johnson. .J. Am. Chem. S o c . , 7 7 , 2098 ( 1 95.5). ( 0 , Ref 3 , p. 1 0 .
( 7 ) t.11. Wallace and J. E. Willard, ibid., 73, 5275 (1950). is! F. I'eipl, "Qualitative Analysis by Spot Test," E l s e v i ~ rF'ublishing Co., K.Y., 3rd English ed., 1940, pp. 49-51.
"greaqe chloride"). I-Tonevcr. tlic ma!l per cent. reduction of activity on distillatinn 4 i o c 11 in rou 4 mid 5 of Table I suggest< that t h c w u a s little organochloride impurity present and that the (9) A. A l l i l l e r and J E TI illard, J C i r m Pi /s
17, lrib (1919)
KOTES
April, 1960 greater per cent. reduction in our other runs w a y probably due to accidental contamination of the CCI, phasc with traces of the highly active aqueour phase or some other radiocontainiiiaiit. The high relati1;e purity of the exchange system may be inferred a l ~ ofrom the fact that the equivalents of HC1 found was only 0.4-0.77, of the equivalents of C1, (in mitrast to 7 and 15% in Schulte’s two runs). The HCI can arise from Clz attacking H20 or stopcock grease in the system. Unpublished experiment iwe have made on the HCl*-CC14 exchange under comparable conditions indicate that it mould caontribute less than 1% based on the upper limit.; for oiir specific dark exchange rates. For the lattcr dark exchange we may take k 3X see.-’ and l i b 8 x lo-” liter mole-’ sec.-’ as conservative upper limits a t
