UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

The chemisorption of chlorine by activated charcoal Godson, Warren Lehman 1941

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1941_A8 G6 C4.pdf [ 10.51MB ]
Metadata
JSON: 831-1.0062279.json
JSON-LD: 831-1.0062279-ld.json
RDF/XML (Pretty): 831-1.0062279-rdf.xml
RDF/JSON: 831-1.0062279-rdf.json
Turtle: 831-1.0062279-turtle.txt
N-Triples: 831-1.0062279-rdf-ntriples.txt
Original Record: 831-1.0062279-source.json
Full Text
831-1.0062279-fulltext.txt
Citation
831-1.0062279.ris

Full Text

THE CHEMISORPTION Off CHLORINE BY ACTIVATED CHARCOAL toy Warren Ldhman Godson A Thesis submitted i n P a r t i a l F u l f i l m e n t of The Requirements f o r the Degree of MASTER OF ARTS i n the Department of CHEMISTRY The U n i v e r s i t y of B r i t i s h Columbia A p r i l , 194P Page No. Intr o d u c t i o n 1 A Proof of Chemisorption of Chlorine By Ac t i v a t e d Charcoal. Part I: Adsorption Theorems. 5 A Proof of Chemisorption of Chlorine By A c t i v a t e d Charcoal. Part I I I temperature Desorption. 19 Conclusions 37 Suggestions f o r Future Work 38 Summary and Abstract , 45 Acknowledgement 46 Bib l i o g r a p h y 47 ' THE GHEMISOfiPTIOI OF CHLORIKE BY ACTIVATED OHARCOAI by Warren Lehman Gfodson i n t r o d u c t i o n . For a very complete a n a l y s i s of and bibliography on a c t i v a t e d charcoal, reference may be made t o my t h e s i s "The Preparation of Active Charcoal By Chlorine", A p r i l , 1939. i n t h i s i n t r o d u c t i o n I s h a l l r e s t r i c t myself t o d i s c u s s i n g experi-mental observations. 1 Perhaps the e a r l i e s t work was that of Berthelot and P e t i t who prepared a chemically pure carbon by passing dry c h l o r i n e over heated charcoal and l a t e r heated the charcoal i n a gas furnace under reduced pressure. While attempting to prepare amorphous carbon fr e e from 2 hydrogen, Mixter observed that charcoal r e t a i n s some ch l o r i n e even at a red heat, although i t loses i t a l l at a white heat. The production of hydrogen c h l o r i d e seemed to i n d i c a t e that the c h l o r i n e had reacted with the hydrocarbons i n the charcoal, (or, i n the case of an a c t i v a t e d charcoal, with the surface h y d r i d e s ) , i t was, therefore, obvious to Mixter that c h l o r i n e had replaced hydrogen i n chemical combination with carbon, since i t eould only be removed by heating i n vacuo at a very high temperature. 3 S i m i l a r l y , r i u f f , .Kimrott and Zeumer found that c h l o r i n e and bromine were so f i r m l y combined wi t h t a r - f r e e wood charcoal that evacuating f o r one hour at l e s s than 1 mm. pressure at the same temperature as that at which combination took place (600° - 800°G) did not remove any considerable amount of halo-gens. B o i l i n g with a ten per cent s o l u t i o n of sodium hydroxide for-.one hour removed pr.ac t i c a l l y none of the c h l o r i n e . They concluded that a halogen complex r e s u l t e d from s u b s t i t u t i n g halogen f o r hydrogen atoms chemisorbed on the charcoal or present i n i m p u r i t i e s . 4 While a c t i v a t i n g charcoal by c h l o r i n e , winter and Baker found that prolonged heating at 900°C or higher gave a better adsorptive charcoal ( i . e . , removal of chemisorbed c h l o r i n e atoms j . I n d i c a t i o n s of a chemical union were a l s o found by 5 6 Eenglein and Orzenkowski end by Okatov , as i n d i c a t e d by d i f f i c u l t i e s i n complete desorption. Mention might a l s o be made of the evidence of Lamb and 18 Coolidge that a l l organic compounds containing c h l o r i n e fpoison" a charcoal surface whereas other compounds have no such e f f e c t . This would i n d i c a t e some attachment of the ch l o r i n e atoms to the surface of the charcoal. As might be expected from such q u a l i t a t i v e r e s u l t s , q u a n t i t a t i v e measurements have served to o f f e r f u r t h e r evidence of chemical combination of c h l o r i n e w i t h the charcoal surface i . e . , of chemisorption. To date, the only s i g n i f i c a n t measurements of the heat of adsorption of chl o r i n e on charcoal are due to ICeyes and 7 Marshall who reported an i n i t i a l heat of adsorption of c h l o r i n e which they thought approximated the heat of combination of car-bon w i t h c h l o r i n e . At 0°C Keyes and M a r s h a l l report an average • ' H = -32,000 eal/mol f o r adsorption of c h l o r i n e at aero con-c e n t r a t i o n ( i . e . , truee chemisorption o n l y ) . From the data of 16 Bodenstein and G-unther we may c a l c u l a t e /..•. H f o r r e a c t i o n C + 201 2 , G 0 1 4 ( s o l i a ) at 0°C. This y i e l d s : fl =-34,120 c a l . (with a maximum er r o r of - 500 c a l . } . Thus, H/mol. CI,, =' -17.060 c a l . , which i s considerably l e s s than the heat of ad-s o r p t i o n , i n d i c a t i n g that at the very low concentrations i n v o l -ved the chemisorption takes place on surface or exposed atoms i . e . , i n t e r i o r G-C bonds are not broken. Since f o r each mol. Clg u n i t i n g with -jkJ one C-C bond must be broken, we may add -77K Cal to / H •« -17K C a l g i v i n g *V H ( l free valence C) * -94K C a l . Since experimentally a heat of -32 to -36K C a l . was observed, i t i s obvious that a p a r t i a l s a t u r a t i o n of the one free valence bond/carbon atom must take place. I f we assume the f r e e valences on the surface are mutually saturated t o the extent of forming G=C bonds instead of 6-6 the heat of r e a t i o n / mol.Clg would be: -17 - 122 + 77 « -62K C a l . Obviously our heat of chemisorption i n d i c a t e s that the p a r t i a l s a t u r a t i o n of "free valence ! t bonds i s not i n the nature of carbon to carbon double bond formation but involves s a t u r a t i o n by several C atoms. This concept appears more evident i f we consider an i r r e g u l a r l a t t i c e , rather than a plane surface, as being more representative of charcoal, f o r i n t h i s case the angles of d i s t o r t i o n of such "bonds would not be so great, and hence there would be a lower heat of dissociation:::to free a bond from the enclosing s a t u r a t i n g p o t e n t i a l f i e l d . 17 I t may be noted that Berthelot and Guntz reported an ad-sorption heat of 13000 eal/mol at pressures up to 1 atmosphere which i s c e r t a i n l y a chemisorption heat, being.approximately _ three times the heat of vapourisation of l i q u i d c h l o r i n e . Isotherms have been determined by s e v e r a l i n v e s t i g a t o r s and w i l l be discussed i n some d e t a i l l a t e r on. Although a l l a v a i l a b l e evidence i n d i c a t e s strong surface forces between c h l o r i n e and charcoal, no l o g i c a l thermodynamic and chemical proof of chemisorption has been off e r e d . Hence i t i s the object of t h i s t h e s i s to e s t a b l i s h an argument for chemisorption that s h a l l be u n a s s a i l a b l e * - 5 -A PROOF OF GHEMISOBPTIG1' OF CHLORIHE BY ACTIVATE]? CHARCOAL :' Pa r t I: Adsorption Isotherms. A. Thermodynamic Introduction. Measurements of adsorption isotherms enable one to c a l -culate any thermodynamic f u n c t i o n . The Enthalpy Change, or the heat of the r e a c t i o n at constant pressure, /\ H, may ei t h e r he measured d i r e c t l y or c a l c u l a t e d from the Clausius-Clapeyron Equation: (dlnp) » • .H„ or I n pp = ,-6,.H (1 - 1) (a«J?.)0 Tfr* 2 pj.- T T (\ i|) . The i r e e Energy Change, />. F, i s obtained by assuming a perfect gas below atmospheric pressure: F = RT In pj> - RT I n ^ e q u i l -P l ibrium Hence the change i n Entropy> ,4 S, may be e a s i l y evaluated from the r e l a t i o n : S * :%H - F T and other functions c a l c u l a t e d i f requar ed. The s i g n i f i c a n c e of these values i s n a t u r a l l y the f i r s t question to be asked. In almost every case of adsorption & decreases with i n c r e a s i n g concentration. The values at zero concentration may i n d i c a t e approximately the nature of the so r p t i o n (for example, the value of a H. f o r c h l o r i n e at zero concentration). Other instances of adsorption heats, however, have only a r e l a t i v e s i g n i f i c a n c e , but do t6nd to approach a l i m i t i n g value as the pressure increases, corresponding to a simple p h y s i c a l adsorption i n most instances. S i m i l a r l y , F (6) decreases ( i n a negative sense, since 4F mast be negative f o r a spontaneous reaction) w i t h i n c r e a s i n g concentration. Indeed, the f a g a c i t y can do l i t t l e more than m i r r o r the adsorption isotherms i n respect to the adsorptive power of an adsorbent f o: the adsorbate. I n the case of 4 S values, on the other hand, we can ne i t h e r p r e d i c t nor expect any marked v a r i a t i o n w i t h concentration; and, because of t h i s , 4. S values take on an i n t e r e s t i n g character, being s p e c i f i c to a considerable con-c e n t r a t i o n range. The s i g n i f i c a n c e of such concepts may be i l l u s t r a t e d by the f o l l o w i n g t a b l e which gives the values of concentration, pressure, 4 H, F and 4 S f o r the adsorption of Chlorine on S i l i c a Gel as c a l c u l a t e d from the isotherm data of Magnus and M u l l e r 8 at 4G°C. TABLE I Adsorption of Chlorine by S i l i c a Gel (40°c) C f M i l l i -MQls (gm) p (mm Hg) . H(Cal/Mol) . F(Cal/Mol) S(Cal/°c/Mol) 0.2 98.5 -6,297 ' -l',272 " -16.06 0.2 160.5 «6,360 -968 -17.53 0.4 226.5 -6,210 -752 -17.45 0.5 296.5 -6^068 -586 -17.51 0.6 368.7 -5,605 -450 -16.47 0.7 445.1 -5,600 -333 -16.82 0.8 523.1 -5,687 -232 -17.41 0.9 602.5 -5,785 -144 -18.01 1.0 686.5 -5,704 -63 -18.00 As we see, the v a r i a t i o n of.., S from the mean of 17.0 i s nevermore than::; 1 Entropy u n i t s , which might be considered quite normal. Once we have decided to assign some importance to » S values, we consider whether we may a r r i v e t h e o r e t i c a l ^ at values f o r M S which w i l l enable us to e s t a b l i s h the nature (7) of the adsorption forces involved. I n the f i r s t place, i t i s conceded that the weakest, forces of adsorption, or Vander Waal forces, are comparable to condensation forces and we may con-s i d e r p h y s i c a l adsorption to consist of a condensation on the surface or i n c a p i l l a r i e s such that the vapor pressure at any concentration equals the e q u i l i b r i u m or adsorption pressure. This concept enables us to c a l c u l a t e a A S f o r p h y s i c a l adsorp-t i o n . On the other hand, i t i s conceded that the strongest forces of adsorption, or chemical valence f o r c e s , are com-parable to chemical combination forces and we may consider Chemisorption to consist of a formation of a surface compound, not n e c e s s a r i l y of constant composition, such that the disso-c i a t i o n pressure equals the e q u i l i b r i u m or adsorption pressure. This concept enables us to c a l c u l a t e a ,. S f o r Chemisorption. How we have merely to compare * a value of ,4 S from adsorp-t i o n data w i t h these two t h e o r e t i c a l extremes to decide on the nature of the adsorption forces in v o l v e d . N a t u r a l l y , the borderline between p h y s i c a l and chemical forces i s not d i s t i n c t , since both are probably dependent on the ultimate e l e c t r o n i c s t r u c t u r e of the atoms. Hence we may also expect r e s u l t s l y i n g between these two t h e o r e t i c a l extremes, corresponding to secondary valence forces of a strong nature. B. P h y s i c a l Adsorption Entropy of Chlorine To obtain a condensation entropy we must obviously calcu-l a t e the ,6. S change on compressing Chlorine to i t s vapor pressure and then condensing i t . (8) dQ = Tds - an - vdp dS •* dH - vdp , at constant temperature ijr- -gr-S - _H - vdp S ' 1 The H i n the f i r s t term, the heat of condensation at absolute temperature T, may best be obtained by applying the Clausius-Clapeyron Equation to the vapor-pressure curve of Chlorine over the desired range (0 - 80°C):-M a H dT T(V V- V e) where V v and V e are the molal volumes of the vapor and l i q u i d r e s p e c t i v e l y . m = m - v e ) ap I f We p l o t l o g p against l/T and measure the slope 2.3026 d l o g p - d lnp - dp_ - T 2 . -T 2 dp d( ) dl ) p W p I H - M - M (2.3026) P d f l o g pj c c . atm/°K T d v a e $ d( ) ' Where a v and d e are d e n s i t i e s of vapor and l i q u i d respec-t i v e l y , M i s the molecular weight and p s the vapor pressure of the saturated vapor at temperature T. H » - (70.914)(2.3026) P 3 1 - 1 d f l o g p) T 41.311 £2 d v d e d (l/T) = -(3.9525) P i s I - i d ( l o g p) C a l / o K T 2 a v a e d P = P s The Second term: - 1 vdp must be evaluated from an ' P = 1 (9) equation "of State other than the Perfect Gas Law, since the satu r a t i o n pressures are comparable to the c r i t i c a l pressure. N a t u r a l l y , the more complicated the equation chosen, the higher the degree of accuracy obtained. Since the second term i s considerably* smaller than the f i r s t the equation need not be too complicated. For a l l p r a c t i c a l purposes we may use the Berthelot Equation. pv s M4. 1-ir 9 p_ '.Id ( 1 - 6 To2};; TSF pc W t% L where pc and To are the c r i t i c a l pressure and temperature and R i s the Gas Constant. P=P S p = p s - 1 vdp • - R <' d£ -_9__ R_ Tc (1 - 6To2 } d T / • • / p 128 pc ' p . l ^P^T P p a l r -Rlnpg - 9 R To ( 1 - 6 T c 2 . ( p < , - l ) 128* ¥e F" p } R = .08207 l i t r e - atmospheres / o K f g j 0 . 4 1 7 > 1 o K > P o - 76.1 atm. The r e s u l t s of these c a l c u l a t i o n s , made at 0°C, 20°C, 40°G, 60°C and 80°C are tabulated below: — TABLE I I P h y s i c a l Condensation Adsorption Entropies f o r Chlorine °0 iH/T - !rdpA ,4S (Cal/°l/mol) 0 -15.55 -2.58 -18.07 20 -13.52 -3.62 -17.14 40 -11.97 -4.56 ^16.53 60 -10.31 -5.34 -15.65 80 -8.60 -5.93 -14.53 The necessary aata was obtained from the I n t e r n a t i o n a l C r i t i c a l Tables. 10. 0. Chemisorption Entropy of Chlorine on Carbon. Here we f i r s t c a l c u l a t e the entropy change at a tempera-ture f o r which entropy values are obtainable, e.g. 25°C» Thi do f o r the r e a c t i o n : C ir 2Clg (gas) CCI4 ( s o l i d ) at 25°C. The entro pies f o r C and CIg(gas) are r e a d i l y a v a i l a b l e : Carbon S g g 8 # 1 . 1.39 ( I n t e r n a t i o n a l C r i t i c a l Tables) Chlorine (gas) S g g 8 . i = 53.24 (Giauque as reported to Parks?,Huffman') The entropy f o r s o l i d CC1 4 was c a l c u l a t e d from the data 10 of Latimer , extrapolated from the temperature of fu s i o n , 249°K, to 298.1°K. To do t h i s C p W a s p l o t t e d against T°K and the curve extrapolated to 373°k. The equation of t h i s curve was obtained a n a l y t i c a l l y using some experimental points and some e x t r a p o l a t i o n p o i n t s , (assuming an analogy w i t h the Debye curves f o r s o l i d s ; and expressed i n a pa r a b o l i c form over the desired range. i . e . Cp - a <- bT <*» cT 2 Now dS s d | s OjofllT •4 s = ' £p dT • alnT f bT cT 2 4. 0 where C i s the constant of i n t e g r a t i o n . Hence a S = a l n T 2 ; b(T g- ^  .. c ( T 2 - T 2) . For s o l i d CC1 4: / S 2 4 9 = 39.84 c p • 6.945 0.1468T - 0.0001908T2 11. From 249 to 298.1°K S = 5.90 S298.1 = 45.74 Cal/°K For oar r e a c t i o n S s 45.74 - 1.39 - 2(53.04) s -62.13 S/mol Clg 298.1 = -31.1 Cal/°K To determine S at 0.20, 40, 60 and 80°C we use S = _C£. ^ where Cp = Cp(CCl 4) - Cp (C) - Cp (2Clg) = * o T 2* 8 i . e . S = 0 l n T T gT 2/2 C C p ( C C l 4 ) s 6.945 0.1468T -0.0001908T 8 C p(C) = 1.22 0.00489T -0.00000111T 2 C p(2Clg) = 11.T6 0.01870T -0.0000140T 2 C p = -6.035 0.1232$ - 0.0001757T2 Now, S = -31.1 at T - 298 hence C - -25.7 S = -6.035 InT 0.1232 T -0.0000878T 2 -25-3 This enables us to c a l c u l a t e S f o r any desired temperatures. The f o l l o w i n g table compares these values w i t h the condensa-t i o n entropies p r e v i o u s l y obtained: TABLE I I I P h y s i c a l and Chemical Entropies of Chlorine Sorbed on Charcoal t 0 C 4S (Condensation) ^S(C 2Clg CC1 4 s o l i d ) 0 -18.07 -32.4 20 -17.14 -31.4 40 -16.53 -304 12. 60 -15.65 -29.4 80 -14.53 -28.5 We are only j u s t i f i e d i n saying that such chemical entro-p i e s are of the same order of magnitude (with respect to l i m i t s of entropies) as any expected chemisorption. Our thermo-dynamic c a l c u l a t i o n s were made w i t h graphite, although we might expect l i t t l e d i f f e r e n c e between chemisorption entropies f o r g r a p h i t i c and amorphous carbons. The c a l c u l a t e d entropies are f o r formation of a separate compound GClAj^ - i . e . involve the breaking of £ x £ x 4 = 1C-C bonds 1 x 2 : 1 01 - 01 bonds ana the formation of £ x 4 s 8 0 - 0 1 bonds. However i f due chemisorption does take place I t must involve ( f o r a mol of Clg) the rupture of £ x E • 1 C-C bonds ana 1 C l - C l bonds ana the c r e a t i o n of 2 C-Cl bonds (eaeh bona serves 2 atoms). I f however, a true surfaee oompouna i s formea w i t h unsaturated carbon valences, our.chemisorption entropies w i l l be higher ( i . e . more negative) than those c a l c u l a t e a above. l o r a quant i ^ . - : t a t i v e statement of such an e f f e c t i t wouia be necessary to use a quantum mechanieal technique, f a r beyond the scope of t h i s work. Nevertheless* we have seen that true "free valence" i s extremely u n l i k e l y . The heat of formation of a C-C bond i s 77 K. c a l . of a C-Cis -122 K c a l , as we have seen. Hence the carbon valences, even on the surface, must be mutually s a t i s f i e a to a l a r g e extent, ana the i n t r o d u c t i o n of a c h l o r i n e atom to a carbon atom w i l l be comparable to the formation of a completely c h l o r i n a t e a s o l i a oompouna of carbon(cf d i s c u s s i o n 13. of measured heat of adsorption). I t i s very s i g n i f i c a n t at t h i s time to compare values f o r the formation of s o l i d c h l o r i d e s from s o l i d elements, evaluated per mol. C l g at 298°K. The f o l l o w i n g t a b l e gives as complete a set of entropies as could be calculated from entropy data ( K e l l e y 1 9 . ) TABLE IV Entropies of C h l o r i n a t i o n /mol Gig at 298°K Reaction 2Ag v CI 2(gas) • , 2AgCl -27.7 £C -; Olg / £ CC1 4 ( s o l i d ) -31.1 £Ti^Cl g £TiCl4 ( s o l i d ) -31.3 £Si Gig f £ S i C l 4 ( s o l i d ) -32.0 £Sh Clg , £ S h C l 4 ( s o l i d ) -32.7 2Tfe • Clg v 2T$C1 -34.7 Pb Gig PbClg -36.9 2Hg ( s o l i d ) Clg v 2HgCl -38.7 Zm r Gig • 2IaCl -43.1 2K v Clg , 2KC1 -44.1 These entropy changes are seen to be f a i r l y p r e d i c t a b l e r e l a t i v e l y from P e r i o d i c Law concepts and serve to f u r t h e r evaluate the t e n a c i t y of a "true chemisorption" bond. D. Sorption Entropies of Chlorine on Charcoal and S i l i c a Gel As we have seen (Section A) /\ S may r e a d i l y be c a l c u l a t e d from s o r p t i o n isotherms by a n a l y t i c a l methods. Hence we may proceed to a b r i e f d i s c u s s i o n of various sets of data, the 14. i n v e s t i g a t o r ' s own conclusions and conclusions to be drawn from the /.,> S values, duly c a l c u l a t e d . « 8 Magnus and M u l l e r determined isotherms f o r the adsorption of Chlorine by s i l i c a g e l at 0.20 and 40°C. Reyerson and Wi-l l shart determined such isotherms at 35.9, 51.0, 66.5 and 81.5° They observed no h y s t e r e s i s on desorption, although t h e i r data did not f i t the langmuir equation. The v S values (obtained by averaging over a l l the concentration range) are presented i n the f o l l o w i n g t a b l e : TABLE V Sorption Entropies of Chlorine on S i l i c a Gel Temp.°C R. and W. - S ( l l ) M. and M S(8) Condensation S 0 -20.5 -18.5 -18.07 20 -19.3 r.17.6 7 40 -18.3 -17.0 > 60 -17.4 ^ -16.6 80 -16.7 J -16.3 •—ranges of a c t u a l measurement. Centre values i n v a r i a b l y show the l e a s t v a r i a t i o n w i t h concentration. I t i s obvious from the above table t h a t sorption of Chlorine by S i l i c a Gel c o n s i s t s simply of condensation or some process i n v o l v i n g s i m i l a r f o r c e s - — i . e . the Vander Waal's fo r c e s . We do not obta i n such fortunate agreement between theory and experiment when we consider s o r p t i o n on charcoal. 12 K l a r and f u l l e r determined isotherms f o r the adsorption -17.14 -16.53 -15.65 -14.53 15. of Chlorine on Chlorinated Charcoal at 0°, 20°, and 40°. The charcoal was chlorinated at 415°C and contained 13.1$ Chlorine, combined i r r e v e r s i b l y . Thus they obtained a r e v e r s i b l e adsorp-t i o n since no true Chemisorption could take place. Neverthe-l e s s they obtained d i f f e r e n t i a l heats almost twice those on S i l i c a Gel which they ascribed to a s p e c i f i c i n t e n s i t y of the Chlorinated Charcoal f o r f u r t h e r C h lorine. 13 Reyerson and Wishart made s i m i l a r determinations on a p u r i f i e d charcoal. They observed a decided desorption hys-t e r e s i s at a l l temperatures w i t h a large amount remaining at the lowest pressures. From t h i s and the high d i f f e r e n t i a l heats they reasoned the presence of strong forces of a t t r a c -t i o n between the Chlorine atoms and adsorption centres on the carbon surface. 14 Data at low pressures has also been obtained by A r i i He observed the long time needed to reach e q u i l i b r i u m and regarded t h i s as i n d i c a t i n g that the adsorption of a gas by a porous adsorbent c o n s i s t s of a primary adsorption for p h y s i c a l adsorption) followed by absorption or d i f f u s i o n to give the time r a t e . A c t u a l l y t h i s t h e s i s proves the secondary process to be chemisorption w i t h i t s accompanying energy of a c t i v a t i o n . The data of A r i i on s o r p t i o n rates i n d i c a t e an energy of a c t i v a t i o n of about It.f K o a l . Unfortunately, from a thermodynamic view-point, the data of A r i i proves extremely u n r e l i a b l e and of dubious value. These values f o r A S (obtained as a weighted average over the concentration range) are presented i n the f o l l o w i n g 16. t a b l e : -TABLE VI Sorption Entropies of Chlorine on Charcoal Temp°C jue s o r p t i o n R&W .-. S(13) Z &K S(12) Adsorption R&W S(13) Chemisorp-A r i l S(14) t i o n /-fi 0 *21.9 -25.4 -28.7 -32.2 -32.4 20 -20.3 -24.4 )' -27.1 -30.8 -31.4 40 -18.9 -23.2 -25.7 -29.4. -30.4 60 -17.8 ••• -21.9 -24.6 •• -28.3 -29.4 80 - i 7 . a -20.5 -23.6 -27.3 -28.5 /, — I n d i c a t e s the temperature ranges over which experiment re made. The middle value i n v a r i a b l y shows the l e a s t v a r i t i o n w i t h concentration. On examination of these values we f i n d : (1) The low pressure determinations of A r i i 1 4 y i e l d r e s u l t s f o r /.;• S close to the t h e o r e t i c a l — d u e t o the f a c t that chemisorption i s only to be expected over the i n i t i a l range. (2) The desorption values of Reyerson and W i s h a r t 1 3 l i e very close to our p h y s i c a l entropies (q.v.)—due to the f a c t t h a t desorption i n v o l v e s only the p h y s i c a l l y ad-sorbed c h l o r i n e , r e s u l t i n g i n h y s t e r e s i s . 12 (3) The data of K l a r and M'uller substantiate t h e i r claim that there are i n a d d i t i o n .to Van der Waal forces between Carbon and Chlorine ( i . e . the desorption entropies of (2) ) C e r t a i n s p e c i f i c r e s i d u a l forces between Chemi-sorbed and p h y s i c a l l y adsorbed Chlorine atoms or even molecules. 17. (4) The s t r a i g h t adsorption measurements of Reyerson and Wishart i n d i c a t e both p h y s i c a l adsorption and chemisorp-t i o n . I t i s very i n t e r e s t i n g to compare these values of A H and :.S w i t h those c a l c u l a t e d from the heat measurements of Keyes 7 o and Marshall at 0 0. Expapolation of v. H to zero ooncentra-o t i o n from isotherms at 0 0 i s extremely inaccurate but r e s u l t s i n d i c a t e a /•,H somewhere between 25,000 and 35,000 c a l . which would probably check w i t h d i r e c t measurement i f low pressure isotherms could be evaluated w i t h any p r e c i s i o n . I f , however, we attempt to evaluate 4> S from simultaneous H and p measure-ments we obtain obviously impossible r e s u l t s of 80 - 90 oal/°K. The reason i s obvious i f we c a l c u l a t e the pressure to be expec-e ted: T S « /« H - /* F A F r />H- T S s RTlnp For ohemisorption fO°C) a S s -324,T/i s' = -8850 c a l . Concentration .01 mm/gm • H = -31,000 c a l . 0.2 mm/gm A H a -24,600 c a l . TABLE 711 C ( m i l l i mols/gm) RTlnp p(atm) p(mm) 0°C AriiJ 4pfmm) 0 C. Calc. 0.01 -22,150 1 0 ~ 1 8 7 . 5 x l 0 " 1 6 1.5 x 10" 4 0.2 -15,750 1.6x10" 1 3 1 . 2 x l 0 " 1 0 3 x 10~ 3 This i n d i c a t e s the i m p o s s i b i l i t y of measuring a true chemisorption pressure. (7) 18. A l l r e s u l t s from Part I are shown on Pig. . C where • S i s pl o t t e d against T f°C). Prom suoh r e s u l t s we may come to the f o l l o w i n g conclusions: (1) Adsorption on S i l i c a Gel corresponds to condensation or Van der Waal's Forces. (8) Adsorption on Charcoal corresponds to both P h y s i c a l Ad-sor p t i o n (Desorption Curve) and Chemisorption ( p a r t i c u l a r l y at low concentrations). (3) Chlorine does chemisorb on Charcoal u t i l i z i n g primary bond to form a C-Cl linkage on the surface. I n Part I I of t h i s Thesis we are concerned w i t h the chemical properties of such a surface complex, w i t h p a r t i c u l a r reference to decomposition temperature. ( i t w i l l be r e c a l l e d that even over 800°C C h l o r i n remained on charcoal.) (19) " A PROOF OF CHEMISORPTION OF CHLORINE BY ACTIVATED CHARCOAL Part I I : Temperature Desorption A. Thermodynamic Intro d u c t i o n . A Thermodynamic•treatment of temperature desorption would seem to be something new i n the f i e l d of s o r p t i o n measurements. Let us consider that adsorption takes place to s a t u r a t i o n at room temperature or lower. Then the temperature i s raised by successive increments while at eaeh stage the charcoal i s out-gassed to a f i x e d pressure (same f o r a l l stages) and the amount of Chlorine desorbed measured by some s u i t a b l e means. Ignoring the desorption run at our zero point temperature we may now take the summation of Chlorine increments up to any given temperature and p l o t against absolute temperature. De-noting Xg as the amount desorbed i n l a s t range up to Tg ( i n concentration u n i t s ) , C as the concentration on the charcoal and S as the s a t u r a t i o n concentration at the zeropolnt tempera-ture (obtained by e x t r a p o l a t i n g summation curve to i n f i n i t y ) ; then: T Xrp ra 2] ^ £ B S—Ctp P l o t x xt$. T and slope dx s - de dT dT Since the e n t i r e operation i s c a r r i e d at constant pressure, (20) We may now p l o t dx r s I — i . e . the ordinate corresponds dt to the p r o o a b i l i t y of escape at any temperature, at a constant fugacity or pressure. That such a p r o b a b i l i t y should not be uniform i s evident i f we consider the f u g a c i t y as a back pres-sure and the a b i l i t y to escape a f u n c t i o n of bond o s c i l l a t i o n s . F i r s t l e t us c a l c u l a t e A H — which w i l l be the heat of desorption at temperature T ( s t i l l a f u n c t i o n of concentration, however). From the Clausius-Glapeyron Equation: d Inp » 4 H dT W 2 AH m RT"7e' Since p = f(c,T) (&js\ = J ^ v / $ Q p But fio\. - - dx ^ / p off Now, we operate our apparatus at a low l i m i t i n g pressure, say -3 (5 10 - 10" • mm. In t h i s range the r e l a t i o n between pressure and concentration degenerates i n t o Henry's law p r k-po ( where k^ , depends on temperature and c c s-x P<3/gv VC/rp S-X '•AH* -RT2(3jo\ ( i > 0 \ P \<5>oJTVJFJp .'. &H = RT 2 ^ dx » HE* dx ' ... p s-x W s - x dT where s,x are obtained from the i n t e g r a l graph,: and dx from W the d i f f e r e n t i a l graph. 21. Obviously a -RT I n p, where p i s oar l i m i t i n g pressure of outgassing. As before A$ m a y b e c a l c u l a t e d to be: A S = AE - Aff and i s an entropy of desorption ( i . e . has a p o s i t i v e value). However s i g n i f i c a n t such thermodynamic values may be, i t i s to the d i f f e r e n t i a l graph that we must r e f e r f o r a d e f i n i t e proof of chemisorption. The p l o t of dx vs I shows us, i n d¥ e f f e c t , how much Chlorine i s coming o f f at any temperature. We would therefore expect t h i s curve to drop o f f quite r a p i d l y at f i r s t as undoubtedly the p h y s i c a l l y adsorbed Chlorine w i l l be the f i r s t to come (of* desorption entropies from Reyerson 13 and Wishart which i n d i c a t e only p h y s i c a l l y adsorbed Chlorine can be removed at room temperatures.) Since we have suggested the formation of a surface compound or complex, we must ascribe to i t chemical p r o p e r t i e s to v a l i d a t e our claim. I t need not, however, have a constant composition since a quantum mechanical concept of s a t i s f a c t i o n of valences can be met i f p o t e n t i a l f i e l d s from more than one Carbon atom contribute to holding the Chlorine atom. Indeed, i f we do not observe a l l the chemisorbed Chlorine coming o f f at one temperature, we must postulate that the complex C x Cly may decompose chemically: C x C l y —> G x 01y_ 2 + C l g . where the s p l i t i s between CI and C, not C-C; and the surface compound C x Cly_g i s more stable than C x Cly since there i s a more concentrated p o t e n t i a l f i e l d a v a i l a b l e to hold the CI atoms Nevertheless, there should be an optimum temperature at which 22. almost a l l Clr-C bonds should break, despite the p o t e n t i a l f i e l d , which may be due to the increased v i b r a t i o n of the C-C bonds, d i s t u r b i n g a steady concentrated p o t e n t i a l f i e l d . Correspond-i n g to such an optimum temperature there should be a marked hump i n the d i f f e r e n t i a l desorption c u r v e — i . e . , p h y s i c a l l y speaking, we expect a rush of gas at that temperature. Before d e s c r i b i n g the apparatus and presenting the experi-mental r e s u l t s there i s one question which should be answered --Can we expect to f i n d and do we f i n d any e q u i l i b r i u m C + 2Clg t=7 CCI4 f g ) . This t o p i c has been c a r e f u l l y inves-15 t i g a t e d by Bodenstein and Gunther who measured the heat of formation of CCI4 (gaseous) and derived the equation f o r the eq u i l i b r i u m constant. Despite the s i m p l i c i t y of the CCI4 molecule Bodenstein and Gunther were unable to e f f e c t an e q u i l i b r i u m synthesis, although some decomposition was observed at 550°C, even between 300-500°C. This i s undoubtedly due to the high Energy of a c t i v a t i o n required which, at room tempera-tures , may be of the same order of magnitude as that calculated 15 from A r i i 1 s data; i e -H-fKcal. as compared w i t h the heat of the r e a c t i o n -33,750 c a l . The f o l l o w i n g table presents the e q u i l i b r i u m constants c a l c u l a t e d and the expected y i e l d s at various pressures. TABLE VI I E q u i l i b r i u m Conditions f o r C + 2 C l g ^ CC1 4 (gas) Temp. K = P C C l 4 / p 2 C l 2 t°C (p i n atm) P = 10" 5 atm. P = 1 atm P=103atm 0 1.0 x 1 0 1 3 0.9999 1 1 23. TABLE VII (continued) E q u i l i b r i u m Conditions f o r C + 2Clg ^ CC1 4 (gas) Temp. t°c K = PCC1 4/P 2C1 2 (p i n atm) P = 10" 5atm. Fraction C C ( 4 P = 1 atm. P - TO 3 100 2.0 x 10 7 • 0. 93 0.9998 1 200 9.3 x 1 0 3 0. 079 0.99 0.9996 300 5.9 x 10 0.0006 0.88 0.996 400 1.6 1.6 x 10-5 0.46 0.975 500 1.1 x 10" 1 1.1 X 10" 6 0.091 0.91 600 1.3 x 10~ 2 1.3 x 10~ 7 0.012 0.76 700 1.8 x 10" 3 1.8 x 10~ 8 0.00125 0.48 800 6.0 x 10" 4 6.2 x 10" 8 6.0 x 10" 4 0.30 900 1.4 x IO" 4 1.4 x i o - 9 1.4 x 10" 4 0.11 1000 6.9 x 10" 5 6.9 x i o " 1 0 6.9 x 10~ 6 0.061 1100 2.9 x IO" 5 9.9 x i o " 1 0 2.9 x 10" 6 0.028 1200 1.35 x 10" 6 1.35 x 1 0 ~ 1 0 1.35 x 10- 5 0.013 We may obtain a rough approximation of the Energy of A c t i v a t i o n at 25°C . i f we consider that t h i s a d d i t i o n a l energy, required before a " p o t e n t i a l hump" i s overcome, c o n s i s t s of the heat of formation of 2 C-C bonds and 2 C l - C l bonds. E = 2 (77)+ 2 (70.4) - 294.8 K C a l . From t h i s the heat of formation of 4 C-Cl bonds i s A Hf * 294.8 - 4 H° r 294.8 - 34.1 « 260.7 K C a l . A.Hf /C-Cl bond = 65.2 K C a l . The Energy of a c t i v a t i o n the reverse r e a c t i o n i s given by: E l + % = E 2 + H 2 24 . . E l = E 2+ A H Eg - E x - A H = 294.8 +• 3 4 . 1 s 328 .9 K C a l . This gives an idea of the magnitude of the energy required and i t i s obvious that carbon, w i t h i t s high quantum, w i l l have l i t t l e p r o b a b i l i t y of obtaining the required energy to disrupt i t s bonds. I t i s also obvious that the C-C bond i s stronger than the G-CT bond even at room temperature: and because of the high quantum f o r C-C and the tendency of the e q u i l i b r i u m to produce Clg at high temperatures, i t i s seen that.at higher temperatures the C-C bond w i l l become r e l a t i v e l y stronger than the C-Cl bond ( i . e . , except f o r s l i g h t surface p o t e n t i a l re-arrangement, desorption should not e f f e c t a clean l a t t i c e to any extent.) We may also ask i f any c a l c u l a t i o n s can be made as to the eq u i l i b r i u m pressure of Clg over a s o l i d carbon-chlorine com-plex . N a t u r a l l y , any such c a l c u l a t i o n s must be extremely approximate as no thermal data i s a v a i l a b l e w i t h respect to the s p e c i f i c heat of such a complex. At 0°C A H = - 68 ,000 (Keyes and M a r s h a l l ) 7 T A S s - 1 8 , 0 0 0 (From L a t i m e r 1 0 and also A r i i 1 4 ) A F = - 50 ,000 s -RT I n K / 2 l o g K s 40 = l o g 1 / P t f P02 = 1 0" 2 0atm. At higher temperatures c a l c u l a t i o n becomes very d i f f i c u l t . An equation s i m i l a r to that of Bodenstein and Gunthee 1 6 y i e l d s at 1000°A, a pressure of 0 . 3 mm. I f one uses the more 25. accurate equation l o g K s • - A Ho - aCp l o g T - 31 4.67 6T 1,987 4.587 and using c l a s s i c a l ideas of s p e c i f i c heats and the value at 0°C, one obtains at 600°A a pressure of 1G0 atm, although the l a t t e r c a l c u l a t i o n seems more l o g i c a l . The Use of Bodenstein and Gunther 1s 1/4.587 (gaseous CCI4) = 3.1 gives a pressure at 600°K of 7.6 mm. Obviously our only check w i l l be to c a l c u l a t e A H from the desorption i s o b a r and i n v e s t i g a t e the l o g K given from reasonable assumptions as to •«> S. Despite true e q u i l i -butVV) a pore, con\\pouV\A *oe u>ool& <js^ " no decomposition owl if -HiC briurn,»*/\equilibrium pressure exceeded the working pressure, at which temperature a l l the compound would decompose (Fig.JL). I f , however, we are dealing w i t h a surface compound of vary-i n g composition, i . e . C x C l y where y i s very large and decreases i n decrements of 2 such that a lar g e number of compounds i s p o s s i b l e , each w i t h a separate decomposition temperature, then there would be no sharp desorption point but a hump i n the curve, f a l l i n g o f f to zero a f t e r C xt31 2 decomposed (P i g . % • ) . As the temperature increases the way i n which the compounds decompose may not give a p e r f e c t l y symmetrical hump but i n general we expect at f i r s t a r a p i d l y i n c r e a s i n g dx/dT followed by a more slowly decreasing dx/dT/\as the f i n a l compounds de-compose. The optimum temperature p r e v i o u s l y mentioned (pag'e'24) w i l l be the maximum point on the curve. As long as the r a t i o y/x remains a r e l a t i v e l y l a r g e f r a c t i o n , the rate , dx/dT, w i l l increase with i n c r e a s i n g bond energies ( i . e . i n c r e a s i n g T) '.' °x G 1 ( y - 2 ) i s v e r y l i t t l e more stable than 0 X C l y . As y/x i s 86. approaching zero, however,the temperature change between de-composition points w i l l increase, despite increased energies: B. Apparatus The apparatus consisted of three p r i n c i p a l p a r t s : (1) a means of introdu c i n g c h l o r i n e to charcoal at any tempera-ture, (2) a means of measuring the Chlorine pressure, and (3) a means of removing and measuring ch l o r i n e desorbed. The apparatus i s shown i n F i g . 4. The charcoal was con-tained i n the quartz bulb, C, attached to the remainder of the apparatus by Quartz-Pyrex graded seals at B and B 1. A l l stop-cocks were l u b r i c a t e d w i t h Apiezon low-pressure stopcock grease, and were not appreciably affeeted by contact at low pressures w i t h Chlorine. The Chlorine was admitted from the tank into the bulb D, the excess flowing through the concentrated l y e s o l u t i o n i n E out to waste. I n t h i s manner a i r could be flushed from the e x t e r i o r system before any Chlorine was admitted to the char-coal and a pressure greater than 1 atmosphere maintained by £7. F i g . 4. Apparatus f o r Measurement of Chlorine Desorp UoV~ 1 f f o i KM Line TKar mo-Couple kcmds Xan&c 4-*j !-4-i| J -/!U F i g . 6 . E l e c t r i c a l C i r c u i t f o r Temperature Control. 1 Fvse Bo* Graded Seal I .Quartz f~'\ Fiber 28. keeping ch l o r i n e babbling i n t o the f l a s k . The chlorine was obtained from a tank of L i q u i d Chlorine supplied by Canadian I n d u s t r i e s L t d . The a c t i v a t e d cocoanut charcoal was obtained from the National Carbon Co., and was the same as used f o r my 1939 Thesis. To measure the c h l o r i n e pressure a s p e c i a l Quartz Fi b e r Gauge, G, was constructed. A side view i s shown i n F i g . 5 here. The f i b e r was approximately 50 microns i n diameter and 8 cen. i n ;. I-• Iron Wire length. O s c i l l a t i o n was induced by mag- <£> l v.v Sealed 4 -f Tube n e t i c p u l l on the J \ tubing containing i i i r o n . F i g . 5 Quartz F i b e r Gauge The- Gauge was c a l i b r a t e d w i t h / a i r using a McLeod Primary Gauge, F, and a l i q u i d - a i r t r a p , H, to keep Mercury vapor from the Quartz F i b e r Gauge. The Gauge i s s e n s i t i v e over a range -8 -5 from 10 to 10 mm, readings depending only on the molecular weight of the gas or vapor. The chlorine was pumped o f f by a mercury d i f f u s i o n pump backed by a rotary pump. The chlo r i n e was c o l l e c t e d i n a U tube containing Potassium, heated by a micro burner. The U-tube was f i t t e d w i t h ground glass j o i n t s and so constructed that the tube could be moved out when needed. The se a l was effe c t e d by P i c e i n cement, a low pressure hard wax. The temperature of the quartz tube was maintained by a Platinum wound, Alundum core resistance furnace, c o n t r o l l e d by 29. a " O a p a o i t r o l " — c a p a c i t y r e l a y actuated by an e l e c t r o n tube. A Chromel-Alumel thermocouple recorded the temperature on the instrument, which maintained a constant set temperature, under average conditions, by i 0.5°. The "Oapaoitrol" (manufac-tured by the Wheelee -Instruments Go., Chicago, U.S.A.) ope-rated on a proportioning basis, a c e r t a i n percentage on and a c e r t a i n percentage o f f four times a minute, the r a t i o depend-in g on the recorded temperature as compared to the set tempera-tu r e . To prevent the on-off arrangement from producing too great changes i n current, the instrument was placed i n p a r e l l e l w i t h a resistance (not when heating up furnace.) so the change i n current was r e l a t i v e l y small. This enabled a more d e l i c a t e temperature maintenance. For future reference the c i r c u i t employed i s given i n F i g . 6. Power i s supplied by a 130 V Variae (operating on 110 V A.C.) and current measured by an Ammeter (max. reading 5 amps.) 0. Experimental For these experiments the corrected weight of the char-coal i n vacuo was...21.792 gm. Reference should be made to my 1939 t h e s i s f o r McLeod Gauge Ratios and Gas P i p e t t e C a l i b r a t i o n and f o r small details of technique. The c a l i b r a t i o n of the Quartz F i b e r Gauge using a i r and a McLeod Gauge as primary standards was c a r r i e d out at various pressures. The l o g a r i t h m i c decrement of the amplitude of v i b r a t i o n of the f i b e r was c a l c u l a t e d from time-amplitude measurements using a cathetometer. 30. The equation of the gauge i s : pJ~M z £1 +- kg And t = K l o g . a i where a s are amplitude a 2 t s time'5 between a^ _ , a 2 •"• * l / 2 - K l°g 2 K = logarithmic decrement For a i r , using the l o g a r i t h m i c decrement since i t can be c a l -culated more d i r e c t l y from any measurements. P a i r = a-, a P X Hence i f p i s p l o t t e d against l / K a s t r a i g h t l i n e w i l l be obtained and the constants r e a d i l y c a l c u l a t e d : Slope = a]_ p i n t e r c e p t = a g , l/K i n t e r c e p t s - ^ / a , -3 Below 10 we obtain a s t r a i g h t l i n e , above t h i s pressure the c a l i b r a t i o n curve must be used since departures from the l i n e a r r e l a t i o n s h i p are found. The f o l l o w i n g table gives p, l / K values. Table V I I I p x 105 mm l / K X 1 0 4 Seo" 1 2 3.94 8 5.07 12 5.51 16 6.74 21 7.72 45 11.89 The graph of these pts i s a s t r a i g h t l i n e w i t h : l / l c i n t e r c e p t - 3.54 x 10~ 4 a - a g a l 3 1 . Slope • 0 .501 s a]_ v\ a1 m 0 . 5 0 1 , a 2« —1.773 x 1 0 - 4 For a i r J~M s 5 .38 (M • 88 .96) p \PM~ = 8 .700 - 9 .57 x 1 0 ~ 4 K p i n mm, K = t / l o g a i , t i n seo. For Chlorine M = 7 0 . 9 1 4 , JM S 8 , 4 2 p 0 .3806 - 1.136 x 10" 4 The U-tube technique should be described next. The Po-tassium Metal was removed from the kerosene, washed i n Ben-zene, scraped clean i f necessary and placed i n the U-tube, whMi i s then cemented i n t o the ground glass connections. The amount used v a r i e d as the temperature range selected and must be suf-f i c i e n t to give a large surface area. The Potassium was then, outgassed w i t h d i f f u s i o n pump and cau t i o u s l y warmed u n t i l a l l gas desorbed. Then a mir r o r was formed up the sides of the U-tube and thoroughly degassed before use. A f t e r the run, the U-tube was removed (by warming the j o i n t s ) and the contents dissolved c a u t i o u s l y i n d i s t i l l e d water. I f a residue remains t h i s and the p r e c i p i t a t e are disso l v e d i n cone HNO3 and the r e s u l t i n g s o l u t i o n treated according to a modified procedure o u t l i n e d l a t e r &t may be mentioned here that except f o r a run at room-temperature no HgClg or HggGlg were ever detected a n a l y t i c a l l y i n the U-tube, and henas the HNOg so l u t i o n s were free from C I - . Natural-l y warming had to be done very c a r e f u l l y to avoid l o s i n g HC1). 32. Phenolphthalein was then added and the s o l u t i o n (of KC1 and KOH, c h i e f l y ) n e u t r a l i z e d w i t h d i l . HNOg. To estimate the Gig removed: 2K + Gig -> 2K01 Use was made of the Mohr Method f o r a n a l y s i s of Chlorides. To the s o l u t i o n Ice of a 5% s o l u t i o n of Potassium Chrornate, KgCrO^ was added and then the s o l u t i o n t i t r a t e d w i t h approximately O.I.N. AgNOg s o l u t i o n u n t i l the c o l o r changed from yellow to orange. The AgNOg s o l u t i o n was standardized against C P . KC1 to reach s i m i l a r end-points. Vigorous a g i t a t i o n i s necessary f o r 1-2 minutes at the end-point to ensure that a l l c h l o r i d e has p r e c i p i t a t e d . I t was noted that the AgCl coagulated about 1 oc before the end-pt and that running a blank (and then sub-t r a c t i n g ) would give r e l i a b l e r e s u l t s . I f a c h l o r i d e o f Mercury had been present i n the U-tube the aci d s o l u t i o n was n e u t r a l i z e d w i t h cone. NaOH s o l u t i o n and s u f f i c i e n t excess added to p r e c i p i t a t e a l l the Mercury. The f i l t r a t e was then "treated as above and no d i f f i c u l t i e s were encountered. For c a l c u l a t i o n i t was convenient to convert the normality of the standard s o l u t i o n i n t o mioromols Clg /gm charcoal / oc standard s o l u t i o n . P r i o r to the 2 runs described here the charcoal had re-ceived considerable outgassing at temperatures over 1000°C and one f l u s h i n g w i t h Chlorine followed by prolonged outgas-sing at 1100°G (see 1939 t h e s i s f o r f u l l e r d e t a i l s of char-coal's h i s t o r y ) . Before the f i r s t run, the charcoal was again outgassed and then allowed to come to e q u i l i b r i u m w i t h a i r . 33. The f i r s t run was effected by passing i n Chlorine to displace the a i r , r a i s i n g the temperature to 1000°C and maintaining a flow of 3 bubbles /see. f o r 8 hours. Then the charcoal was cooled i n a current of chlorine and t r a n s f e r r e d to the desorp-t i o n apparatus (which was not as e f f i c i e n t as that i l l u s t r a t e d and employed i n run #2). Then the temperature was r a i s e d by i n t e r v a l s of 100-125°C and desorption c a r r i e d on f o r 6-16 hrs. Chlorine was analysed as o u t l i n e d . A t a temperature over 1250°C the bulb collapsed and the apparatus was p a r t i a l l y redesigned as i l l u s t r a t e d f o r Run #2. P r i o r to Run #2, the charcoal was outgassed f o r 60 hrs. at 1150°C; then 5 months l a t e r 130 hrs. at 1000°C, 40 hrs. at 1050°C (p s 50 x 10~ 5 mm). 20 hrs. at 675°C (p = l x l 0 ~ 6 mm.) Chlorine was admitted to the vacuum at 1078°C f o r 1 hour, then the charcoal cooled f o r 1-g- hours in'" the presence of excess c h l o r i n e . At room temperature (24°C) Chlorine was pumped o f f f o r 75 hours, then a s i m i l a r procedure t o Run #1 followed up to 1200°C, f o r times of 16-50 hrs. The Quartz F i b e r Gauge was used to ensure a constant f i n a l pressure. Ether and s o l i d COg may be placed i n a Dewar at the base of the gauge to en-sure that no pressure of a m a t e r i a l l e s s v o l a t i l e than c h l o r -ine exerts any pressure (although i n time such m a t e r i a l s w i l l be completely removed). There may be a pressure below which the time i s too great or the l i m i t i n g pressure may depend on the pressure i n the U-tube of the heated Potassium (which should eliminate mercury vapor i n the re s t of the apparatus). 34. In the l a t t e r ease the Chlorine pressure i s l e s s than the t o t a l pressure ( s t i l l a constant f o r each run.) The U-tube contents were analysed and the thermodynamic treatment set f o r t h i n Section I I A applied. Results f o r Run #1 were only used as a guide f o r Run #2 procedure. D. Results. Results of Run #1. may be best, i l l u s t r a t e d by the fo l l o w -ing t a b l e . S i g n i f i c a n c e of the r e s u l t s w i l l be deduced c h i e f -l y from Run #2. TABLE IX Desorption Results of Run #1. F i n a l Temp./°C No.Hrs Xp (mm/gm) X s 2. Xg (mm/gm) dx/dT (mm/gm/°G dx/dT IOC 6 236.6 236.6 0.80 IDEAL 200 6 55.9 292.5 0.34 325 6 23.7 316.2 0.08 0.033 450 7 26.3 342.5 0.35 0.009 550 8* 42.6 385.1 0.406 0.017 650 10 36.2 421.3 0.439 0.055 750 46.5 467.8 0.461 0.157 850 15 44.4 512.2 0.483 0.387 950 15 35.1 547.3 0.493 0.667 1035 15 49.0 596.3 0.472 1155 16 48.9 645.2 0.305 1275 12 22.8 668.0 0.102 The r e s u l t s are p l o t t e d i n F i g . s 7 and 8. The "idea] curve" i s ca l c u l a t e d by e x t r a p o l a t i o n of the p h y s i c a l adsorp-35. t i o n i n t e g r a l curve and the chemisorption i n t e g r a l curve, e l i m i n a t i n g the middle p o r t i o n which i s probably due to c h l o r i -nated hydrocarbons being expelled ( i . e . a halogen a c t i v a t i o n . ) This assumption i s borne out by the r e s u l t s of Run #2. Results of Run #2 are presented i n the f o l l o w i n g table and f i g u r e s .9 and 10. Obviously these r e s u l t s are of much greater s i g n i f i c a n c e than those of Run #1. TABLE X Desorption Results of Run #2. F i n a l Temp(°C) No.Hrs. x?(mm/gm) X = 2.Xp. dx/dT(mm/gm/°C) 24 75 930 0,0 15.0 112 19 66.5 66.5 0.310 187.5 16 15.3 81.8 0.126 343 17 11.9 93.7 0.0687 480.5 21 11.0 104.7 0.0730 ... 625.5 3 8 i 10.9 115.6 0.0940 801 46. 21.1 136.7 0.1555 897 42 16.0 152.7 0.2016 1002 48 26.4 179.1 0.2865 1100 48 20.4 199.5 0.1511 1211 90 10.1 209.6 0.0470 From the graph.S(saturation desorption amount) = 213.5 mm/gm. Broken Lines i n fi g u r e 10 represent extrapolated true p h y s i c a l adsorption and true chemisorption curves. The o p t i -mum temperature of desorption i s observed to be 1000°C (the temperature at which chemisorption was i n i t i a t e d ) . A l i m i t i m 36. pressure of 3.x I O - 3 mm. was used throughout. C a l c u l a t i o n s o f ^ H and A f were made, using the r e l a t i o n s AH = RT 2 dx s-x M A F = TABLE XI -RTlnp A H and A F from Run #1 T °K x mm/ gm s-x mm/gm dx/ dT mm/gm/°C AH Gal/mol A F Cal/M 373 236.6 438.4 0.800 504.5 8,843 473 292.5 382.5 0.340 395.2 11,210 598 316.2 358.8 0.080 158.4 14,180 733 342.5 332.5 0.350 1093 17,140 823 385.1 289.9 0.406 1885 19,510 923 421.3 253.7 0.439 2929 21,880 1023 467.8 207.2 0.461 4627 24,250 1123 512.2 162.8 0.483 6626 26,620 1223 547.3 127.7 0.493 11,470 28,890 1308 596.3 78.7 0.472 20,390 31,010 1428 645.2 29.8 0.305 41,470 33,850 1548 668.0 7.0 0.102 69,380 36,700 At 373°K the caloula ted A S f o r condensation i s -13.6 Cal/°K/Mol. This means that A H should be: AH = 4 F 4- T AS = 8,843 -v- 5074 = 13,917 c a l . The lar g e discrepancy e i t h e r casts doubt on the method or i n d i -cates that the desorption forces are very small. This l a t t e r should not be true (of. Reyerson's measurements). I t might i n d i c a t e that even p h y s i c a l desorption requires a long time f o r e q u i l i b r i u m to be reached. 37. TABLE XII AH and & F from Run #2 Tf°K) x(mm/ gm) s-x(mm/gm) dx/dT AH(Cal/Mol) AFfCal/Mol) 297.1 0 213.5 15.0 12,320 7,345 3 8 5 i l 66.5 147.0 0.310 621.4 9,521 460.6 81.8 131.7 0.126 403.3 11,390 616.1 93.7 119.8 0.0687 432.5 15,230 753.6 104.7 108.8 0.0730 757.1 18,630 898.6 115.6 97.9 0.0940 1541 22,220 1074.1 136.7 76.8 0.1555 4641 26,650 1170.1 152.7 50.8 0.2016 10,795 28,925 1275.1 179.1 34.4 0.2865 26,900 31,520 1373.1 199.5 14.0 0.1511 40,430 33,940 1484.1 209.6 3.9 0.0470 41,890 36,690 Although dx/dT f o r 24°C (297.1°K) i s only very approximate, i t gives a AH which seems reasonable. We can c a l c u l a t e A S , AS = A I 16.75. At 24°C the A. S f o r p h y s i c a l condensation of Chlorine i s -17.0, which checks w i t h the A.S c a l c u l a t e d from the is o b a r . I n other regions A S seems to have l i t t l e or no: s i g n i f i c a n c e . The c r i t i c a l temperature of Chlorine i s 417°K or 144°C so above t h i s temperature p h y s i c a l adsorption would not involve condensation fo r c e s , but merely a t t r a c t i v e f o r c e s only s l i g h t l y l i m i t i n g the degrees of freedom of the C1 P molecule. 37. S. Conclusions. From Ron #2 we may conclude that.: 1) Chemisorption of Chlorine i s a r e a l i t y . This i s i n d i c a t e d by the i n t e g r a l desorption curve and i s of the order of 110 mm/gm charcoal at normal temperature independent of Charcoal pressure, since the e q u i l i b r i u m pressure i s immeasurably low, of the order of IO--*-5 atm. as we have pr e v i o u s l y c a l c u l a t e d . This corresponds to an "a c t i v e centre" surface of 2 sq. metres/ 20 1 gm (approximately the same as found f o r oxygen by McMahon p-i and Cook .) Hence only about £ of 1% of a l l surface a v a i l a b l e carbon atoms are s u f f i c i e n t l y " a c t i v e " or oriented to chemi-sorb C h l o r i n e . 2) The surface complex i s of a wide range of s t a b i l i t y , w i t h 1000°C as an optimum temperature of desorption. This i s seen from the d i f f e r e n t i a l desorption curve and suggests the great d i f f e r e n c e i n a c t i v i t y to be expected f o r the "act i v e centres." 3) The purpose of Chlorine as an a c t i v a t o r i s i n f e r i o r to Oxygen. As i s i n d i c a t e d from Run #1 and previous work already quoted, Chlorine can combine w i t h hydrocarbons i n the charcoal and at the high temperatures of a c t i v a t i o n would a s s i s t i n breaking up t h e i r molecular s i z e . Outgassing removes these Chlorinated products and hence cleans the surface. Unlike Oxygen, however, Chlorine cannot break the Carbon-Carbon bond and increase the unsaturation of the surface. Hence repeated Chlorine treatments should not increase the " s u p e r - a c t i v i t y " of a charcoal. Nevertheless a r e l a t i v e l y clean and pure sur-face i s doubtless produced since by 1300° the Chlorine would 38. seem to have been completely removed. 4) The formation of Carbon Tetrachloride by d i r e c t union of the elements i s seen to be extremely improbable, due to the high energy of a c t i v a t i o n required t o break a Carbon-Carbon bond. G. Suggestions f o r Future Work. 1) To data on change of A H w i t h temperature apply thermo-dynamic a l equations to obtain the s p e c i f i c heat of the surface complex. Compare such values w i t h quantized degrees of f r e e -dom and observe the e f f e c t of decreasing y i n C x C l y as w e l l as temperature. In t h i s respect the data of Garner on Oxygen heats at varying temperature might be examined (of. #6). Ob-served data on graphite or amorphous charcoal and f o r gases w i l l enable the s p e c i f i c heat of the complex to be determined. 2) Further runs. Try to obtain tne e q u i l i b r i u m pressure and measure i t s change w i t h temperature. Nature of e q u i l i b r i u m pressure w i l l f a c i l i t a t e choice of l i m i t i n g pressure ( i . e . such that a high temperature pact of complex decomposes i n several ranges.) Work out ratio..; y/x from data on desorption of G XCly. Once an e q u i l i b r i u m pressure has been reached constant concentration measurements may be made (corrected f o r volume of apparatus and then reduced to previous concentration by Henry's Law—which may be checked at any one temperature). The concentration can be determined from a subsequent outgas-sing at highest temperature plus a c o r r e c t i o n f o r remaining 39. Chlorine from runs i n t h i s t h e s i s , a ( l o g p)/a(-^} = - A H / R w i l l give us a A H f o r a p a r t i c u l a r surface complex which could be compared with those of t h i s t h e s i s . This may be re-peated f o r various concentrations as long as measurements of pressure can be made w i t h the Quartz F i b e r Gauge. I f possible a d i r e c t way of admitting known concentrations should be de-v i s e d — i . e . admitting to f i b e r gauge cut o f f from charcoal, measuring pressure f o r c a l i b r a t e d volume, then admitting to charcoal and remeasuring pressure. A d i s t r i b u t i o n of bonding energies could be c a l c u l a t e d i f the pressures of the various complexes could be obtained at a reference temperature say 1000°C. Perhaps the Entropy change might be u t i l i z e d to evaluate the thermodynamic proba-b i l i t y of the state and the A H or A . F to give a measure of the a c t u a l energies involved. T h e . d i f f e r e n t i a l desorption curve gives the amount desorbed f o r any temperature i n t e r v a l , which could be transposed to corresponding energy values and a d i s t r i b u t i o n curve of the bonding energies of "a c t i v e centres" f o r Chlorine p l o t t e d . 3) Experiments i n d i c a t i n g activated adsorption or chemisorp-t i o n might a l s o be t r i e d . Complete desorption runs could be made w i t h the Chlorine added to charcoal at temperatures from 0°C tof20G°G, f o r varying amounts of time, p a r t i c u l a r l y since t h i s t h e s i s showed an optimum temperature of desorption at the higher temperature of admission of Chlorine. Furthermore, d i r e c t a d d i t i o n at various temperatures could be studied w i t h respect to the time rate of change of pressures and a c t i v a t i o n 40. energies c a l c u l a t e d . From Langmeitr1 s concept of e q u i l i b r i u m w i t h a monomolecular l a y e r , modified f o r constant f u g a c i t y of chemisorbed atoms, c a l c u l a t e to see i f a t h e o r e t i c a l rate i s e s t a b l i s h e d . S i m i l a r l y f o r the reverse r e a c t i o n , assuming a.pressure f o r the pump, i n v e s t i g a t e the dechemisorption ra t e , f o r a s p e c i f i c surface complex, and determine the energy of a c t i v a t i o n f o r i t . From these two energies the H can be cal c u l a t e d (see Page 24 ) and compared w i t h those obtained from the desorption isobar and Clausius-Clapeyron equation. Results s i m i l a r to Taylors on a c t i v a t e d adsorption should be obtained i n every respect, w i t h the ac t i v a t e d adsorption d e f i n i t e l y e s t a b l i s h e d as chemisorption. S t a r t i n g at low temperatures, p h y s i c a l and chemical adsorption can be measured from the rate and a f i n a l concentration a r r i v e d at by use of a s u i t a b l e formula; s t a r t i n g at the higher temperatures only chemical adsorption of the unsaturated surface bond type can be measured. At intermediate points i f the v e l o c i t y i s suf-f i c i e n t l y great values should i n d i c a t e a decomposition accor-ding to C 2 n C l 2 n —*> C gn -v- n C l g t which should have decomposition pressures s i m i l a r to those c a l c u l a t e d (see pagert-) A f t e r a v a i l a b l e surface atoms have taken up Chlorine there should be a slow chemisorption i n v o l v i n g a c t u a l breaking of bonds (of. Og breaking G-C bonds). The Energy of A c t i v a t i o n w i l l therefore be much greater than f o r the case of p a r t i a l l y unsaturated a v a i l a b l e bonds. 4) I n connection w i t h work of t h i s nature may I suggest a l i t t l e c l o s e r d e f i n i t i o n of terms, w i t h two a d d i t i o n s ; fa) S o r p t i o n — a generic term to cover a l l cases. fb) Physisorption--a s p e c i f i c term to cover cases of adsorp-t i o n under the influence of Van der Waal's c a p i l l a r y or condensation f o r c e s . By d e f i n i t i o n , entropies of physi-sorption must c l o s e l y approximate condensation entropies ( i . e . condensation to l i q u i d or s o l i d state.) fo) P h y s i c a l A d s o r p t i o n — a more general term to cover cases of adsorption of a strong e l e c t r o s t a t i c or dipole nature f i . e . adsorption of p o l a r compounds on i o n i c l a t t i c e s ) or p h y s i c a l forces stronger than condensation; i . e . , se-condary atomic forces and miscellaneous molecular f o r c e s ; i n c l u d i n g a s p e c i f i c i t y of a monomolecular l a y e r f o r f u r t h e r adsorption, not purely condensation. P h y s i c a l Adsorption entropies w i l l not be lower than condensation entropies. fd) Chemisorption--a s p e c i f i c term to cover cases of adsorp-t i o n , under the influence of primary valence forces, to form d e f i n i t e surface compounds or complexes w i t h a v a i l -able p a r t i a l l y unsaturated bonds. Due to t h i s f a c t the chemisorption entropy should be higher than that ca l c u -l a t e d assuming the rupture of completely saturated bonds fe) Chemical A d s o r p t i o n — a general term to cover cases of adsorption of a d e f i n i t e l y chemical nature i n v o l v i n g strong atomic forces and secondary forces which are strong enough f o r apparent union f i . e . adsorption of an i o n on an i o n i c l a t t i c e ) . Such an entropy w i l l i n 48. general be l e s s than a t h e o r e t i c a l chemical entropy. The term might be used to cover any case where a f u l l rupture took place ( i . e . exchange adsorption) i n which case the entropy would c l o s e l y approximate the t h e o r e t i c a l chemical entropy. I n other cases we are on the borderline between p h y s i c a l and Chemical adsorption since chemical forces have t h e i r foundation i n a purely p h y s i c a l sub-atomical array. 5) Work might be done on the desorption curve f o r Hg as re-83 ported by Lowr-y U5in<j the above derived thermodynamic pro-cedure and assuming a l i m i t i n g pumping pressure. I n t h i s con-ne c t i o n i t would be important to examine the Hg-rC-GH^. e q u i l i -brium w i t h which much recent work has been done (of. Parks and (9) Huffman. ) A l i m i t i n g pressure of Hg assuming a s o l i d hydride might be deduced as w e l l as an expl-antion f o r the removal of Hg not CH 4 ( c f . Og - GO and GOg only can be removed; i.e.,the 0-G bond i s stronger than the G-G bond).. Since normal a c t i v a -ted charcoal y i e l d s Hg only at the highest outgassing tempera-ture such a study would have some bearing on the r e s u l t to be expected from outgassing. For removal of 0 g see McMahon's Thesis. 6) I n xhe case of Og, complexes: a very accurate determination 20 of the desorption isobar has been made by McMahon i n h i s recent t h e s i s . This could be analysed according to the thermo-dynamic technique derived and information concerning bond strengths obtained. To examine the chemisorption at room 43. temperature a, dn approximate chemisorption entropy could be obtained by comparing values of A s/mol. Clg and A S / M o l . Og forming s o l i d c h l o r i d e s and oxides w i t h various metals. Such Entropy data i s a v a i l a b l e and a reasonable value f o r A S on Carbon could be obtained by a weighted method of proportion. A t the l e a s t , l i m i t s could be set f o r A . S on Carbon i n r e f e r -ence t o other elements of the P e r i o d i c Table. Use could be 21 made of the recent heat reported by Cook i n h i s t h e s i s , s i m i l a r to the use of the heat of adsorption of Clg by Marshall i n t h i s t h e s i s . 7) A more accurate e x t r a p o l a t i o n of the s p e c i f i c heat f o r GCI4 (and a high temperature equation) might be ca l c u l a t e d by examining the c o n t r i b u t i o n of Carbon i n s o l i d compounds stable at high temperatures on the basis of a v a i l a b l e degrees of freedom and by examining the s p e c i f i c heat c o n t r i b u t i o n of Chlorine i n s o l i d c h l o r i d e j a t various temperature ( i . e . NaCl, etc.) 8) Very important and s i g n i f i c a n t would be a study of Bromine and Iodine under s i m i l a r conditions to Chlorine i n t h i s pre-sent t h e s i s . S i m i l a r techniques could be used throughout, although adsorption heat data i s not a v a i l a b l e . For t h e o r e t i -c a l c a l c u l a t i o n s any a v a i l a b l e data on CBr4 and CI4 could be used or such values c a l c u l a t e d by analogy to CCI4. Isotherms f o r Brg and I2 on both S i l i c a Gel and Charcoal have been de-24 termined by Reyerson and Cameron': and entropies could be ca l c u l a t e d from t h e i r data. P h y s i c a l or condensation entro-p i e s could also be ca l c u l a t e d from vapor pressure data. As a 44. r e s u l t the chemisorption of both Bromine and Iodine could doubtless be e s t a b l i s h e d . 9) A point which would be very i n t e r e s t i n g to e s t a b l i s h i s .the difference i n free energy and entropy f o r Graphite and Charcoal. E q u i l i b r i u m data w i t h Hg f o r these two forms i s a v a i l a b l e but do not admit of a very accurate treatment. Heat of combustion have been measured, however, and some approxi-mation could be obtained. Another method which could be used involves the freer-, energy change on expansion of graphit to amorphous Carbon. The value df p f o r Graphite has been determined and two methods f o r determining the l i m i t s of i n t e g r a t i o n could be compared. D e n s i t i e s could be used or else X-ray d i f f r a c t i o n data, which y i e l d s the s i z e of the "amorphous" c r y s t a l l i t e s and the r e l a t i v e plane separations. A Quantum Mechanical treatment i n v o l v i n g p u l l i n g atoms apart against a p o t e n t i a l f i e l d might also be used. Hence A F could be c a l c u l a t e d and so we know A H, A S could also be c a l c u l a t e d . A s i m i l a r treatment of the Diamond could be compared to Lewis and Randall's values. 45". SUMMARY AND ABSTRACT This research was i n i t i a t e d to study the chemisorption of c h l o r i n e by activa t e d charcoal, u t i l i z i n g a thermodynamic treatment. C a l c u l a t i o n s were made on t h e o r e t i c a l entropies of physi-c a l adsorption ( i . e . condensation) and chemisorption ( i . e . formation of s o l i d c h l o r i d e of carbon). C a l c u l a t i o n s were made on observed entropies f o r adsorption of Chlorine on S i l i c a Gel and charcoal. I t was found that adsorption on S i l i c a Gel corresponded to condensation, and adsorption on charcoal corresponded to both P h y s i c a l Adsorption (desorption values) and Chemisorption ( p a r t i c u l a r l y at low concentrations.) Experimentally, desorption isobars at low pressures were determined and d i f f e r e n t i a l desorption curves p l o t t e d . These indica t e d a t o t a l amount ehemisorbed at normal temperatures of 110 micromols/l gm. charcoal; ( i . e . , approximately -§• of 1% of the a v a i l a b l e surface comprised "a c t i v e centres"). Fur-thermore, the curves i n d i c a t e d that desorption of ehemisorbed atoms commenced between SOO—300 °C and reached a maximum at 1000°C, being complete between 1250 and 1350°C (10~ 3 mm pressure). The i m p r o b a b i l i t y of a d i r e c t synthesis of Carbon Tetrachloride was shown from a v a i l a b l e data. The mechanism of halogen a c t i v a t i o n was explained on the basis of removal of hydrocarbons, not of r e o r i e n t a t i o n of Carbon atoms. 46. AQCTOWLESGEKffimT I wish to take t h i s opportunity to thank Dr. M. J. M a r s h a l l , who d i r e c t e d t h i s research, f o r h i s keen i n t e r e s t and suggestions, many of which are to "be found i n the t h e s i s , and f o r h i s assistance with the "building of the apparatus. 4-1. BIBLIGGRAPHY f l ) Berthelot and P e t i t ; Ann. GMm. Phys. : (7) 18,80—1889 (2) M i x t e r ; Am. Jour. S c i . : (3) 4S, 363--1893 (3) Ruff, Rimrott and Zeumer. K o l l o i d Z. : 37, 27G —1925 (4) Winter and Baker; J . Chem. Soc. : 117, 319 —192G (5) Henglein and Grzenkowski; Z. Angew. Chem. : 38, 1186-1925 (6) Okatov. Zhur. P r i k l a d n p i Chim. : 2, 21 --1927 (7) Keyes and M a r s h a l l . J . Am. Chem. Soc.: 49, 156 --1930. (8) Magnus and M a i l e r . Z. Phys. Chem. : 148A, 241 — 193G. (9) Parks and Huffman, "The Free Energies of Some Organic Compounds," 1932. (10) Latimer. J . Am. Chem. Soc. : 44, 90 — 1922. (11) Reyerson and Wishart. J . Phys. Chem, : 41, 943 -- 1937. (12) K l a r and M u l l e r . Z. Phys. Chem. : 169A, 297 -- 1934. (13) Reyerson and Wishart. J. Phys. Chem. : 42, 679 —1938. (14) A r i i . B u l l . I n s t . Phys. Chem. Research (Tokyo): 19, 148—1940. (15) A r i i . B u l l . I n s t . Phys. Chem. Research (Tokyo): 17, 717— 1938. (16) Bodenstein and Gunther. Tr. Am. E l e c . Chem. Soc. : 49, 226 — 1926 (17) Berthelot and Guntz. (Compt. Rend: 99, 7 — 1884 (Ann. Chim. Phys. : (VI) 7,138—1886 (18) Lamb and Goolidge. J . Am. Chem. Soc. : 42, 1146 —1920. (19) K e l l e y . Bur. Mines B u l l , : 350, 63. (20) McMahon. Thesis, U n i v e r s i t y of B r i t i s h Columbia, 1937. (21) Cook. Thesis, U n i v e r s i t y of B r i t i s h Columbia, 1939. (2.2) Garner and McKie. J . Chem. Soc. : 2451 — 1927. (2S3) Lowry. J . Am. Chem. Soc. : 46, 824 -- 1924. (24) Reyerson and Cameron J . Phys. Chem. : (39, 169 — 1935 (40, 233 — 1936 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
https://iiif.library.ubc.ca/presentation/dsp.831.1-0062279/manifest

Comment

Related Items