XOTES
500 TABLE Iv H E ~ OI( T SOLUTION ~ OF XaBrOs(c) RIolcs XaBrOs X lO3,'QZO
AHa(kca1 /mole)
ml
9 3488 6 47 11 5816 6 46 15 7812 6 48 11 402 6 45" 15 885 6 47' 19 157 6 46" a T7alues were obt:tined by Mr. M. 31. Birky of this Laboratory. hlr. Birhv's work n a s done on a tpice-recrystalh e d sample nhich had been oven-dried a t 100" for several hours.
with the data in Table V to calculate the standard heat of reaction 5. HEATSOE
I I I I1
IthALTION O F
I1
3.7850 4.9985 3 . 9051 5,1491 4,2295
I11
:J.0487
T4BLE I&,(C)
v WITH SOLUTIOXb O F
1.999 1.909 1.999 2.499 1.099 1.499
KOH
-26.39 -26.52 -26.36 -26.34 -26.38 -26.45
XI1 of the standard heats of solut'ioii (equat'1011s 1-4) anti reaction (equation 5 ) are given iu Table T'I. Our estimates of lota2 uncert'aint,ies, including uncertainties in compound purity, experimental heat determiiintioiis and heats of dilution, indicated by =t, are also given in Table VI, TABLEVI STAXDARU HEATSO F SOLUTION AND REACTION Erlrintion number
1 2 3 4 5
d!lbsr3nci~
SII,IC)a(c) 9aI03( c )
IiIOl(C) SaBrOs( c ) I ~ O ; , ( C ) 2OH-(aq)
+
A H~(kcal./niole)
7.m 4.83 6.63 6.4 -26.4
* 0.12
.06 .05 i .06 i .% f f
Discussion and Calculations lT7hile this research was in progress,- Russian workers"J report,ed heat's of solution of 1I-IJOa(c) in agreement with our values ; therefore further attempt,s to prepare very pure XH4103(c) were abandoned. We know of no prior determinations of heats of solution of S a I 0 3 ( c ) or n'aBr03(c). Heats of solution of KIO,(c) ranging from 5.57 to 6.78 kcal./ mole have been reported." We know of no prior determinations of the heat of reaction of IzOb(c) wit,hexcess OH-(aq). The ent'ropygp." :Lnd s ~ l u b i l i t y 'of ~ IiIO:i(c) are l;no\vn. We ha1-e t'almi the activit'y coefficient of IVeu Soulh I'C'ales lusliiilzn
R e c e n e d S o r e m b e r 11 1959
The data in thiq note iupplemeiit previoudy published results for the conductancc of hydrochloric acid and hydrogen ion i n aqiieous wrrope and mannitol solutions3-5 by providing values in 5 , 10 and 207, glycerol solutions. Experimental A4n:tlytical rcngent quality glycerol W I Y tliliitetl with dotibly-distilled water (specifir ronductnnrp 1-2 X ohm-' cm.-I) to prepare several stock solutions slightly more concentrated than the desired values of 5 , 10 and 2OC' respectivelv. These \$ere each passed through a mix bed ion-ewhange resin.& Then the conccntrxtion of ea solution was o h i n e d by romp:iring thc mcasured dt sity with values from the literaturc.6 Thr literxture data gave specific gravities caleiilated from n cighinps not corrected for air buovanry ( a correction ~vvhic~his unncccssxrv belom- a SOWo glyrerol concentration). For t h r piirposcs of the present work the sperifie gr:tvitirs w w convcrtctl t o densities taking 0.99707 g /ml. D P th(, d r n ~ i t vof wrtrr a t 25'. T h e dc,nsit omposi t ion tint a 111iii o ht:iinf,d wrrv fitted, for r : ~ e h of c w l r:ingcIs of eomlmition, hv the ( 1 ) Presented, in part. in a tlirvis suhrnittrrl in lirtrtial fiilfilln~cntof the requirements of tho Vnirersity of New- En~.ianilfor the degree of Iloctor uf I'hilosojihy. (2) Department of C'heiiiistry, University of \\'isconsin, Rlildisoii 0, Wisconsin. ( 3 ) J. RI. Stokes a n d R. H. Stokes, THISJOGESAL, 60, 217 (1050). (4) J. hl. Stokes and R. H. Stokes, d i d . , 62, 497 (1958). tal R . .J. Steel. J. 31. Stokes and R . H. Stokes, i b t d . , 62, 1514 (19551. (0) >I. Sheely, I n d . Eng. Chem., 24, l O G O (1932).
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 should read X o 239.2 and R = 0.884. =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 ) .
