NOTES
Oct., 1961 i< 104 i. mole-' cm.-l. The mean value of 3.54 X IO4 cm.*niole-l was used to get quantum yields. The Hanovia S-I00 lamp was used with Corning 7-51 and 0.52 filters to solate the 3660 A. light. A compound filter F t h single crystal salt slices* wae used to isolate the 3130 A. line. Short exposures were used to produce form C which was measured in the t,pectrophotometer. Thermal fading of form C during exposure and before measurement waa insignificant for this compound. From the light absorbed and the amount of colored form produced the quantum 1 xlrl way calculated.
rvhc,re = absorbance = log I,,/I. -4,and A , = find and initial absorbance t = 3 54 >: I O 4 1. mole-' cm.-'
I: 3
= time in sec.
current chrtnge ($amp.) for spiran soln. in cell phototube sensitivity 10.9 x 109 /.ramp. sec. einstein-1 v = 3.14 X 10-8 1. 1.11 = corr. for light beam area on cathode hi
S
= =
1909
DETERMINATION OF THE IONZATION CONSTANTS OF SOME PHENYLMERCURY
COMPOUNDS BY S. S. PARIKS AND THOMAS R. SWEET Department of Clre?nistrg, The Ohio State Unircrsify. Colunibira IO, Ohio Receised April 80, 1061
For many years the effects of various phenylmercury compounds on plants and animals have been studied. The purpose of this work is to determine the ionization constants for phenylmercuric acetate and phenylmercuric propionate. These constants were obtained by potentiometric titrations of phenylmercuric hydroxide solutions with standard acetic acid and propionic acid solutions. In order to calculate these values, the ionization constant for phenylmercuric hydroxide was needed. This value has been report,ed by Waugh, Walton and LnuwicP and also was redetermined in the present work.
Experimental Reagents. Phenylmercuric Hydroxide .-This was obtained as a chemically pure sample from Metalsalts Corporation. Its purity waa checked by the following analyses: %C, theor., 24.45; exptl., 24.61, 24.67; %€I, theor., 2.05; exptl., 2.21, 2.23; %Hg, theor., 68.07; exptl., T.4BLE O F rrYPICAL RUNS 67.80, 68.07, 68.25. An equivalent weight of 295.66 was Phototube determined by adding an excess of KBr and titrat.ing with current, standard acid.* The theoretical equivalent weight is 204.72. Concn. --PamAbmilliA, Time, De- sorbance Phenylmercuric Hydroxide Solution .--A weighed quanmolarity 1. ~ c . Initial crease change .$ tity of phenylmercuric hydroxide was transferred to a volumetric flask. Carbon dioxide-free nitrogen gas was 0.0 3130 . . . . 10.8 1.0 ... :3130 60.09 11.2 ,03977 5 . 3 0.055 0.15 passed into the flask for one hour to flush out all carbon dioxide gas in the flask. Carbon dioxide-free water was ,3977 3130 100.07 10.65 9 . 2 .140 . I 3 added until the flask was about three quarters full and the 3660 60.08 14.7 5.1 .!I3977 ,045 .13 liquid was brought t o near boiling until all the phenylmer:36iiO 80.12 1 5 . 6 13.4 ,3977 .122 .10 curic hydroxide went into solution. During this time and 56 36 17.3 .3977 Above5400 .I1 also while the solution way cooled to room temperature and 11.3 .073 diluted to the mark with distilled water, nitrogen waa passed in a t a slow rate. The solution was standardized The average quantum yield for the change from form B by adding about 4 g. of potassium bromide to 50 ml. of the to form C of an ethanol solytion of this spiran a t 3130 A. solution. Phenylmercuric bromide precipitated and the free hydroxide was titrat,ed with a standard perchloric acid is 0.15 i 0.07 and a t 3660 A. is 0.12 f 0.06 mole/einstein. The uncertainty results from uncertainty in the extinction solution. Preliminary Studies.--It was apparent that a saturated coefficient. If :I. highly colored solution is formed and allowed to potassium chloride salt bridge should not, be placed directly stand, the color fo.dc>s. At 26.5' the first-order rate con- into the phenylmercuric hydroxide solut,ion since this stant is 7.5 i J..0 X 10-4sec.-1. At 6'' it was found t o would result in the forniation of insoluble phenylmercuric chloride and a consequent change in pH. For this reason sei:.-l which gives an act,ivation energy of he 4.18 X a saturated sodium nitrate salt bridge wm used. In order 23 kcal. When the colored solution is irradiated with visible light, to prevent contact of carbon dioxide with the solution, photofading occur8. The quantum yield for the visible nitrogen gas was continuously passed into the cell compartlight from the S I 0 0 !:imp through a 3-69 filter was 0.10 =t ment. However, when a 0.01 Af phenylmercuric hydroxide solution was titrated with 0.01 M H N O sunder these condi0.06. Sirice visible light P L I ~effect, the fading it tieems possible tions, a small amount of precipitate was observed in the solution and also on the t,ip of the 3alt bridge. This was th:it ultreviolet si:sorh(a,i I Jthe ~ color form might also be effwtivc. If it, is, the photostationary state would have attributed to the formation of phenylmercuric nitrate. perchloric acid solution was uscd with When a 0.01 l e ~ scolorcd form than otherwise. The equation for the a 0.01 M p!ien,ylmercuric hydroxide solution, no precipitate pl1otoststion:wy rate can be written was observed in the solut,ion. A thin film of precipitate C B I S = k[CI &IC could be seen on the tip of the sodium nitrate salt bridge (2) if the salt. bridge was left in contact with the phenylmercuric where hydroxide soiution for severs1 minutes. The error resulting . . from this source was minimized by taking only one pH thc tiiermrtl fading rate constant reading witli each dalt bridge-phenylmercuric hydroxide . !!gilt .Liisoi,!xd psr liter per second solut,ion combinntion. When 0.01 r?l phenylmercuric uttd siihscripts refer to the non-colored (B) and colored (C) hydroxide was titrated with 0.01 AI acetic acid or 0.01 Af iorms. Pb,ptoat,stionary states were measured for 3660 propionic acid, the solution appeared thc ssme as described .inti 31XU -4.. light which gave quantum yields +c, of 0.4 ahove for the 0.01 Af perchloric acid. .:.iicl '3.7 ;!.,(;le,'eiiistein. This increase in +C with energy Procedure.-.$ %O-ml. beaker with a. fii-: hole rub!)?r .pi-,.jiirtntn w i n s reaponahie. For 3130, 3660 and 5400 A. , 78.1 and 59.2 kca!./einstrin. (11 Taken in part from the master's thesis of S. S. Pnrikh jireseqted shows only a small shift to the i n the G r a d u a t e School of The Ohio State Univcraity. 1)eeernbrr. ! 5 0 ' s ~ )that AH must be small.
Values were obtained for 3130 and 3660 A. and for soluuons 0.3977 and 0.03977 millimolar a t 26.5' and typical data are elioivn in the table.
+
1'. D. V a i r g h , €I. Y. W a l t o n and J. A . Laswiok. J . I'hys. Ch-n.,
I): T;illiorn MrBriile of thew !aboratorieci.
NOTES
1910
stopper and a 150-ml. beaker were placed in a water-bath maintained a t 25 f 0.04". The holes in the stopper of the larger beaker were used for a nitrogen gas inlet tube, a buret tip, a gas outlet tube, a Beckman blue bulb glass elec40495), and one arm of a sodium nitrste salt trode (KO. bridge. The other arm of the salt bridge was placed in the 150-ml. beaker This beaker contained a saturated solution of sodium nitrate and a Beckman saturated calomel electrode. Carbon dioxide-free nitrogen was passed into the dry 250-1nl. beaker to displace all carbon dioxide. Nitrogen was passed into the beaker continuously until after the reading was obtained, thus keeping it carbon dioxide-free and stirring the solution. Fifty ml. of phenylmercuric hydroxide solution was transferred to the 250-ml. beaker and a known volume of standard acid solution was added from the buret. After the solution was thoroughly mixed, a saturated sodium nitrate salt bridge was introduced and the pH was determined immediately. The entire procedure was repeated for the next volume of acid. Each time a pH reading was obtained, a new salt bridge and a new phenylmercuric hydroxide solut ion wPre used.
Results Table I shows the data and results for the ionization constant of phenylmercuric hydroxide. The average of the three values closest to the half equivalence point was 1.3 X 10-lo and this is taken as the best value for Kb. I n the table, THCIO,and Z'P~,H~OH indicate, respectively, the total added perchloric acid concentration and the total added phenylmercuric hydroxide conrentration after correction for dilution.
Vol. 65
+
+
The ionization constant K for phenylmercury acetate was calculated from the equations [PhHg+] = TPhHgOH
0.00 5.02 10 00 18.38 25.09 28.24 34.00
7.63 5 04 4 66 4.29 4.04 3.94 3.71
0.998 1.755 2.824 3.512 3.793 4.254
8.610 7.920 6.949 6.328 6.073 5.656
1.42 1.02 1.29 1.33 1.31 1.30
In developing the equation used for calculating results, these equilibria were considered
+
PhHgOH = PhHg+ OHOHH20 = H +
+
By combining equat,ions for coriservation of species, electrical neutrality and ionization constants, an equation was obt,ained Kw2
Kb =
~
[H+I
+ K W T " ~ i o-r K,[H+l
.-~_________
[H+!Ti,hH,on
- KW -
[H+l T H C I O 4-~[H'F
A K , value of 1.008 X was used. Table I1 shows the data and results for the ionization constant for phenylmercuric acetate. The average of t,he three values closest to the half equivalence point is 1.5 x and is taken as the best value. In developing the equations for calculating the results, these eq,uilibria were considered (3) H. S. Harned and B. B. Owen. "The Physical Chemistry of Electrolytic; Bolutionu," Reinliold Publ. Corp.. N e w York, N. Y., 1958, p. 638,
[H+12 KW - THO&+ - - -- + K, K.
-
KW -~ [Hi]
w_-_ [H+] _K_ _
K,
[H'IKb [OAC-] = [H+] [PhHgOAc]
=
KW + [PhHg+] - 7 [H I
TrloAo- [OAc-]
+ 11
[PhHg+][OAc-] K = [ PhHgOAc]
A Ka value of 1.754 x low5for acetic acid4 and a Kb value of 1.31 X for phenylmercuric hydroxide were used in these calculations. TABLE I1 IONIZATION CONSTANT O F PHENYLMERCURIC ACETATE Normality of acetic acid = 0.01008; molarity of phenylmercuric hydroxide soln. = 0.009503; initial vol. of phenylmercuric soln. Volume of acetic acid added
0.00 TABLE I 2.67 IONIZATION CONSTANT FOR PHENYLMERCURIC HYDROXIDE Normality of perchloric acid = 0.01055; molarity of phenylmercuric hydroxide solution = 0.009503; initial vol. of phenylmercuric hydroxide sol. = 50.00 ml.
+ +
PhHgOH = PhHg+ OHOAcPhHgOAc = PhHg+ HOAc = H + OAcH20 = H + OH-
10.74 20.00 24.71 28.02 33.00
PH
7.63 6.25 5.70 5.43 5.29 5.20 5.02
=
50.00 ml.
TBOAC
x
101
0.510 1.784 2.881 3.334 3.620 3.780
TPI~HPOH
x
103
K
9.030 7.821 6.788 6.360 6.090 5.399
x
105
0.82 1.57 1.45 1.47 1.48 1.48
Table 111shows the data and results obtained for the ionization constant of phenylmercuric propionate. The average of the three values closest to the half equivalence point is 3.1 X lop5 and is taken as the best value. TABLE I11 IOXIZATION COXSTANT FOR PHENYLMERCURIC P R O P I O X A T E Normalitv of propionic acid = 0.01321 ; niolxrit,y of phenylmercuric hydroxide soln. = 0.009299; initial vol. of phenylmercuric soln. = 50.00 ml. V d u m e of propionic acid added
PH
0.00 5.91 10.31 16.00 17.64 19.60 24.95 29.79 34.43
7.56 5.68 5.47 5.25 5.19 5.12 4.92 4.73 4.55
THOP?
x
108
1.396 2.258 3.202 3.445 3.720 4.397 4.932 5.387
TPhHgOA
x
108
8.316 7.700 7.045 6.874 6.680 6.203 5.827 5.507
K
x
106
3.11 3.12 3.11 3 14 3.11 3.13 3.13 3.00
The equilibria considered and the equations used to calculate the ionization constant for phenylmercuric propionate correspond to those for phenylmercuric acetate. 1.336 X was used as the ionization constant for propionic acid.4 The ionization constants were found t,o be 1.3 (4) Ref. 3. pa 755.
x IO-'" for phenylmercuric hydroxide, 1.5 X 10-5 for phenylmercuric acetate, and 3.1 X for phenylmercuric propionate. Each of these values was found to be constant for experimental points taken 01 er a wide range of (Tacld/TPhHgOH) values. The constant for the hydroxide is further substantiated since it was used in calculating both of the other constants. The value for phenylmercuric hydroxide found in the present work agrees with the value of 1.0 X that has been reported.2 Thwe constants may be used in estimations of equilibrium constants for the interaction of phenylmercury compounds with groups such as the sulfhydryl group in biological materials.
t-
I
SORPTION OF SULFUR HEXAFLUORIDE RY ARTIFICIAL ZEOLITES BY DANIELBERGA N D WILLIAMM. HICKAM V e s t i n g h o u s e Cmtrnl Laboratories, I'ittstiuryh Q 5 , Pmnsylz'ania R e c e i i d .April 86, 1961
The small and uniform size of the intracrystalline pores left, by t,he removal of water from hydrated crystalline zool.ites results in "molecular sieve" act'ion. 31Iolecules of large diameter are excluded from the pores,; smaller diameter molecules may be sorbed in the intracrystalline pores. With mixtures of molecules of diameter smaller than the sieve pore :sizes preferential sorption may take place. Habgood' 'has studied the kinet'ics of Molecular Sieve action for nitrogen-methane mixtures. In this case nitrogen diffuses more rapidly into the small pores and is preferentially taken up in the early stages of sorption but methane has a higher affinity for the sieve and is preferentially sorbed a t equilibrium. In this work we are interested in studying the sorption of a rnolecule of roughly 5 A. diameter, namely, SF,, :is a function of t'emperature and pressure and the selective sorption in mixt'ures of SF6and air. Experimental Procedure A gas circulatclry system wit,h mass spectrometer2 was used in measuring sorption of SF6 by the Molecular Sieve. This system ofler~~ wveral advantages over other equipment used for similar measurements. The calibrated volume and manometer permits accurate determination of the quantity of gas used. The system is attached to the mass spectromtter which providcs analysis of the gas when desired. When mixturw of gases are being used the circulating pump ensures ihiLt the gas abow the sieve is of uniform composition. 'This sondition, eomhined with the mass spectrometric analysis, permits calculation of the quantity of each cornponeizt adsorbed even though there are large teniper3turc gradients in the system due to heating of the sieve. .A weighetl amount of sieve was plxed in the system. T h r sieve vv)~.r ~ \ x t i l t t dand heated to ahout 200" to re. Sulfur hexafluoride wv&sintroduced
r I O it known pressim of i: tn the romvcjir was
SF, :tnd then repeated sev-
: I ) R.W. K>L,goc?, Can. J . Chem., 36, 1384 (1958). (2) L.,;.!
