UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

The heat of adsorption of oxygen on charcoal Branston-Cook, Harold Edward 1925

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

Item Metadata

Download

Media
831-ubc_1925_a7_b7_h3.pdf [ 1.06MB ]
Metadata
JSON: 831-1.0061829.json
JSON-LD: 831-1.0061829-ld.json
RDF/XML (Pretty): 831-1.0061829-rdf.xml
RDF/JSON: 831-1.0061829-rdf.json
Turtle: 831-1.0061829-turtle.txt
N-Triples: 831-1.0061829-rdf-ntriples.txt
Original Record: 831-1.0061829-source.json
Full Text
831-1.0061829-fulltext.txt
Citation
831-1.0061829.ris

Full Text

/he  Heat oF AdsoroHon of^ Oxygen on Charcoal,  h Harold  Edward^Bntmsfbn-Cook  THE HEAT OF ADSORPTION OF OXYGEN ON CHARCOAL by Harold Edward Brains ton-Co ok  A Theaia submitted for the Degree of MASTER OP APPLIED SCIENCE in the Department of CHEMISTRY  THE UNIVERSITY OP BRITISH COLUMBIA April, 1925. a  ff*Ar*U'L<iJtQ,  TABLE OP CONTENTS.  INTRODUCTION. GENERAL EXPERIMENTAL PROCEDURE 1. 2. 5• 4.  Preparation of Charooal Preparation of Oxygen Apparatus Method.  RESULTS. DISCUSSION OF RESULTS. SUMMARY. BIBLIOGRAPHY.  THE HEAT OP ADSORPTION OF OXYGEN ON CHARCOAL.  Introduction The first quantitative work on the adsorption of gases on charcoal was carried out by de Saussure . Since that time many investigations have been prosecuted to determine the quantitative relationships existing between quantity of gas adsorbed, temperature and pressure. In a few cases 2 3 4 5 (Pavre , Chappins , Titoff , Lamb and Coolidge , Blench and Gainer ,) the heat of adsorption has been measured at 7 different temperatures and pressures. Dr. M.J. Marshall , while working on the heats of adsorption of gases and vapours on oharooal, obtained very striking results in the case of low concentration of oxygen. 1.  He found:  that the initial heat values were very high - 70000 cal./ mole/ gm. of charcoal, and the final values very low 4000 cal./ mole/ gm. 2. the first adsorption was characterized by the satisfaction of primary valences, further adsorption resulting from a modification of existing molecular fields. 3. the active surface of the charcoal was very small, approximately 0.5 sq. metres per gm. He used only a a small quantity of charcoal- 8 to 3 gms., and his ice calorimeter could only be relied upon for five hours. Purther, the charcoal used was Prench war charcoal, very likely not the most active available. The present research was instituted in order that the previous conclusions might be checked with a different type"of charcoal, using a larger quantity to enable a closer study of the initial heats to be made, and working under calorimetric conditions permitting a more leisurely study of the heat evolution.  - 2  GENERAL EXPERIMENTAL PROCEDURE. Preparation of Charcoal The charcoal used was a standard sample of activated cocoanut charcoal obtained from the National Carbon Co. Before use it was extracted repeatedly with hydrochloric acid to remove any soluble salts, and then with hydrofluoric acid to remove the silica.  This reduced the  ash content to 0.2668$. Finally it was graded to pass a mesh of cross-sectional area 2.725 sq. mm. and be retained on one 0,689 sq. mm.  Prior to the first run  the charcoal was exhausted at 1000° C. for sixty hours. -4 The final pressure was 1 x 10 cm. at this temperature. The pumps were kept going until the mass had cooled to room temperature.  The exhaustion preparatory to the  seoond run required only ten hours pumping at 1000  C.  Preparation of Oxygen The oxygen was prepared by gently heating anhydrous potassium chlorate containing a trace of manganese dioxide.  In a previous run no manganese dioxide was  used and a severe explosion occurred.  3 -  Apparatus The apparatus used is shown in the accompanying diagram and photographs.  The feature of the apparatus  is the calorimeter, a modification of that designed by p  Sriffiths . It consisted of the galvanized iron container C, the jacket of which was packed with felt; the Dewar flask Df and the Bunsen ice calorimeter B.  The  cork A provided a water-tight seal when the ice calorimeter was lowered into the Dewar flask and this permitted crushed ice to be packed in C up to the top of B. A plug of felt was packed around the quartz tube where the neck of B. level.  it entered  Distilled water was added up to the ice  Using this arrangement an ice mantle was maintained  in B continuously for twenty days. The charcoal was contained in the quartz bulb  £  This bulb was lined with platinum in order to prevent the reduction of the quartz by the carbon at the high temperatures of evacuation. Contact between the walls of the ice calorimeter and the bulb Q was made by means of a film of mercury. A very even ice mantle inside the Bunsen calorimeter was obtained by immersing a long tube containing an etnersolid carbon dioxide mixture was slightly larger than  in the mercury.  This tube  Q . By adjusting the level of  the mercury a mantle of uniform thickness was obtained.  - 4 The performance of the calorimeter was studied for eight days. As a result it wa3 found possible to maintain a constant leak for periods of sixteen - eighteen hours. The absolute value of the leak could be varied by adjusting the room temperature. As a result of studies made during the first run it was determined that the value of the leak increased with additions of gas, the increment from run to run being very small. Values of the leak: :; varying from zero to .03 cm. per five minutes were obtained.  The  crushed ice had to be renewed every twenty-four hours when the room was kept at 20° C.  4*  Method The quartz bulb Q was charged with about 25 gms. of charcoal, exhausted at 1000° C. for several hours, filled with hydrogen, sealed and weighed. exhausted as described above.  The charcoal was again  When this was complete the  ice calorimeter was prepared and the apparatus assembled for a run.  The whole was given two days to stabilize in  before a run was commenced. At first 3mall quantities, less than 1 o.c, of oxygen were admitted to the charcoal. These were increased until about 70 c.c. quantities were admitted.  The heat evolved was measured by means of the*  drop in mercury in the capillary tube. This tube was carefully calibrated on the basis of one mean calorie equal to 0.01549 grams of mercury . A single charge was  - 5 -  studied for a period of from nine to twenty hours.  RESULTS. Two runs were made.  The data are shewn in Tables  I and II. The total calories per gram of charcoal, q, 4 was plotted against total moles xlO of oxygen adsorbed per gram of charcoal, n, on a very large scale. This curte is reproduced in Fig. £.  i'he  tangents to  this curve, Tffi, will give the values of the heat of adsorption at constant volume per gram molecule of gas per gram of oharooal, Q v » a"t "the concentration  n.  These values are given in Table III and plotted in Figure 3. After completion of run B the apparatus was maintained at 0° C. while the gas was pumped off by means of a Topler pump.  The gas was passed through baryta water.  Only a  very slight precipitate was formed. While conducting the preliminary exhaustion to run A, it was noticed that after prolonged exhaustion at 1000° C the charooal and quartz bulb were charged electrostatically with charges of opposite sign.  If a piece of charcoal came  in contact with the quartz it would adhere. By sharply tapping the bulb the charcoal could lie detached and it* would then pass in a curved orbit to a new point on the quartz, maintaining the same general level. After being detached several times it would fall back into the ma3s of charcoal.  - 6 -  DISCUSSION OF RESULTS. Examination of Figure 3 shows that the initial heat of adsorption is very high, 84,400 calories per mole per gram.  This value is higher than any previous value the  highest recorded being 70,000 calories per mole per gram due to Jilarshall. The final values are the same in each case - approximately 4000 calories per mole per gram. In view of the high initial values it would seem that the first quantities adsorbed were held by primary valences, later layers being held by modification of the existing molecular fields. The curve in Figure 3 is also periodic in nature, tending to have steps occur at increasing concentration intervals.  This periodicy gives an explanation  of the phenomenon observed; During the preparation of charcoal the carbon chains existing in the fibres are denuded of their hydrogen but are not much modified, if at all, in form.  The result is  that a certain few atoms will be thrust clear of the aggregate and present a point of intense attraction for the oxygen. Also, although the charcoal has a general porosity, it also contains some pores of molecular dimensions in the carbon chains.  These pores will also represent  regions of intense attraction.  Since the attractive forces  at these points will of necessity be very variable no constant heat value could be expected until they are all  - 7 covered with at least a monomolecular layer. Even then prominent points would have greater attractive properties than the general surface and hence would still tend to attract the  oxygen preferentially.  A constant heat value  would not be obtained until they were saturated, or rather their attractive force reduced to a value represented by the attractive force of the general surface.  Then a general  covering would occur, after which the heat value would be a more or less constant low value.  The point representing  a monoraolecular layer would be the concentration at which the heat values drop off to approximately a constant value. flence, assuming that the first layer corresponds to 1 x 10 grams molecules of oxygen, that E . 6.06 x 10  , and that  the distance apart of the centres of the oxygen atoms is 8 ' 9 1.25 x 10  cms. as shown by Bragg , we can calculate the  minimum surface per gram of charcoal as follows: 3  =  E x lxlO"4 x 6.06X1023 (1.25 x 10"8)  z 1.8937 x 10 4 sq. cm. per gm. m 18.937 sq. metres per gm.  2  - 8 SUIvIMARY  1.  The heat of adsorption of oxygen on charcoal at 0° 0. has been carefully measured over a large range of concentrations, using 25 grams of cocoanut charcoal.  2.  The initial concentrations used are smaller, and the initial heats larger than those obtained by any previous investigator.  3.  The mechanism of adsorption has been discussed.  4,  The active surface of cocoanut charcoal ha3 been calculated to be 18.937 sq. metres per gm.  5.  Charcoal has been heated for sixty hours at 1000° C, without apparent loss of activity, although previous investigators claimed great loss of activity from continued heating above 800° - 900° C.  6.  The activity of charcoal depends more upon the temperature of evacuation than upon the time.  7. Ho appreciable quantity of carbon dioxide is formed when oxygen is adsorbed at 0° C. 8,  Interesting electrical phenomena have been observed after long heating and continued evacuation.  Further work is being done in connection with „ the oxygen results. It is hoped to measure the heat of adsorption of acetylene.  BIBLIOGRAPHY. 1.  Th. de Sauaaure, Gilb. Ann. 47, 113, Annals of Philosophy, 1815, p. 241  2.  Pavre, Ann. de Chim et de Phys (5) 1, 1874, p.209  3  Qhappnfla. W i e d  *  Ann  *  19  » 1883, p.21  4.  Titoff, 3 Physik Chem. 74, 1910, p. 614-678  5.  Lamb and Coolidge. J.A.C.3  6.  Blench and Gainer. J.0.3. 125, 1924, p.1288  7.  M. J« Marshall. Mass. Inst, of Tech., Ph.D. Thesis  42, 1920, p.1146  1921 8.  Griffiths. J. Lond. Phys. S o c , 26, 1913, p.1-14  9.  Bragg. Phil. Mag., 40, 1920, p. 169  10. 11. 12.  Smith. Proc. Roy. S o c , 12, 124,  Comples Jetendu* 139, 261 Lewar, Pfoc. Roy. S o c , 74, 125, Ann.de Phys. et Chem (8) 3,4 Homfray. 3 Phys. Chem., 74, 129, Ptoc. Roy. Soc. A 84, 99  13.  Dewar, Proc. Roy. Inst., 18, 177 and 443  14.  Lemon and Blodgett. Phy. Rev. (2), 14, 281 and 394  \5*  Baerwald. Ann. de Physik 23, 84  16.  Hunter, Phil. Mag. 25, 1863, and J.C.3. 3, 285; 5, 160; 6,186; 8,73; 9, 76; 10, 649  17.  Lowry and Hulett. J.A.C.3.  18.  Brigga, Proc. Roy. S o c , October 1921  19.  ginlay3on. Trans. Inst, of Chem. Sng. 1.3  42, 1408  TABIE I.  Rtm  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20  gas Admitted  0.8728 1.2120 2.4951 0.8466 1.1904 2.0984 2.4501 2.2044 3. 2036 2.2572 3.5713 6.8989 6.8562 10.5830 22.3205 29.4030 45.7284 27.9632 62.3590 77.0983  Wt. of Gharooal a 25.7920 gr. Final Total " Total Heat Pressure gas not Gas c.o. in rom.^ adsorbed adsorbed adsorbed Cal... 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.20 0.34 3.25 7.40 14.73 35.60 83.40 140.00 179.20 271.50 382.20  k  0 0 0 0 0 0 0 0 0 0237 <,0403 ,3860 ,8832 1,,7741 4,,2861 9.,5605 16 ,7946 21 ,6260 33 ,1900 46 .4470 •  i  0.8728 1.2120 2.4951 0.8466 1.1904 2.0984 2.4501 2.2044 3.2036 2.2335 3.5547 6.5532 6.3590 9.6921 19.8085 24.1286 38.4943 23.1318 50.7950 63.8413  0.8728 2.0848 4.5799 5.4265 6.6169 8.7153 11.1654 13.3698 16.5734 18.8069 22.3616 28.9148 35.2738 44.9659 64,7744 88.9030 127.3973 150.5291 201.3241 265.1654  3.203 3.828 7,271 2.350 3.008 6.253 7.162 6.602 9.344 7.637 6.910 11.453 8.631 8.253 6.854 7.036 8.127 4.476 10.434 11.260  Total Heat  3.203 7.031 14.402 16.752 19.760 26.013 33.175 39.777 49.121 56.758 63.668 75.121 83.752 92.005 98.859 105.895 114.022 118.498 128.932 140.192  q  =  oal 1 gm. .1242 .2715 .5584 .6495 .7661 1.0087 1.2862 1.5422 1.9046 2.2006 2.4684 2.9127 3.2472 3.5672 3.8330 4.0954 4.4207 4.5945 4.9990 5.4356  . E x 10 4 = Moles 1 gin. .015115 .036103 .079307 .096694 .114560 .150940 .193340 .231540 .287000 .325700 .404270 .500720 .610800 .778700 1.121730 1.532400 2.206300 2.605550 .3.48780 4.59920  TABLE II. Wt. of Charcoal s 24.8428 gms. Run 1 £ 3 4 5 6 7 8 9 10 11 12 13  Gas Admitted .7572 1.4952 2.4695 3.7552 3.8696 7.4069 11.3680 15.5690 20.4246 67.9940 87.5640 73.2420 75.2550  Final Total Pressure gas not (mm) adsorbed  0 0 0 0 .05 .40 6.85 20.25 43.50 128.20 259.0 374.0 513.9  0 0 0 0 .0060 .0479 -.8202 2.4242 5.2123 15.3671 31.0660 44.9310 61.4760  Total Gas c.c. gas adsorbed adsorbed .7572 1.4952 2.4695 3.7552 3.8636 7.3650 10.5957 13.9650 17.6365 57.8382 72.8651 59.3770 58.7100  .7572 2.2524 4.7229 8.4781 12.3417 19.7067 30.3024 44.2674 61.9039 119.7421 192.6072 251.9842 310.6942  Heat in Cal.  Total Heaf in Cal.  2.966 5.091 8.015 11.274 11.792 20.702 14.910 11.246 5.945 15.290 15.848 11.583 11.400  2.966 8.057 16.072 27.346 39.138 59.840 74.750 93.102 99.047 115.337 130.820 142.403 153.803  3 " , Cal/ gm. 0.1194 0.5243 0.6469 1.0951 1.5754 2.4091 3.0091 3.6091 3.8402 4.4715 5.0715 5.5211 5.9631  R x 10 4 » Moles/ gm. .013614 .040493 .084910 .152420 .221905 .354300 .544775 .795772 1.113000 2.153000 3.462600 4.530000 5.58580  TABLE I I I .  0  0.01 .02 .05 .10 .15 .20 .30 .40 .50 .60 .70 .80  1.00 1.50 2.00 2.50 - 6.0 I  85,200 84,400 81,100 73,970 69,800 68,263 63,165 59,000 42,667 32,500 28,400 19,467 12,217 7,266 5,900 5,166 4,633 4,250  fix 10  

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:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0061829/manifest

Comment

Related Items