HIGH TEMPERATURE CATALYSTS FOR CARBON NIONOXIDE OXIDATION W. H. LOCKWOOD AND J. c. W. FRAZER Department o j Chemistry, The Johns Hopkins University, Baltimore, Maryland Received J u l y 14, 1955
The investigations of Lamb, Bray, and Frazer (20) on catalysts for the oxidation of carbon monoxide resulted in a mixed oxide catalyst, Hopcalite, which completely oxidized carbon monoxide in air a t room temperature and below. Since then numerous materials have been tested by different investigators, and in most instances oxide catalysts have proved superior. Bray and Doss (7) and Almquist and Bray (2) studied copper oxide and manganese dioxide. Bone and Andrew (6) studied nickel and copper and their oxides as catalysts. Taylor and Jones (29) also investigated copper and copper oxide catalysts, while Benton ( 5 ) made a study of several oxides and mixtures. Frazer (12), Whitesell and Frazer (31), Bennett (3), and Loane (23) have shown that highly purified oxide catalysts are more active than mixtures and that the activity depends more on the purity than on promoter action. However, all the catalysts discussed above lose their activity on heating to elevated temperatures, owing either to sintering or to a change in chemical composition. Recently some attention has been directed toward catalysts which would stand heat treatment. Engelder and Miller (10) reported tests of a number of mixed oxides, the best being a mixture of copper and titanium oxides. Engelder and Blumer (9) found that a catalyst composed of cobaltic and ferric oxides was 100 per cent efficient a t room temperature and could stand heating to 890°C. without a decrease in activity. Frazer (11) and Lory (24) have investigated the metsl chromites and found them to be moderately active after heating to high temperatures. I n the present investigation catalysts of the oxide type and catalysts of the chromite type were studied, and it will be convenient to discuss them under two classifications according to whether they were supported or unsupported. The catalysts mere tested by the method described by Loane (23). UNSUPPORTED CATALYSTS
Chromites The chromites were prepared by the ammonium chromate method which has been used in different modifications by Lazier (22), Adkins and his 735
736
W. H. LOCKWOOD AND J. C. W. FRAZER
coworkers (1, 8), and Lory (24). Molar weights of chromic anhydride and the metal nitrate were dissolved in water, precipitated with 3 moles of ammonium hydroxide, the precipitate filtered, washed with 250 cc. of water, and dried in an oven a t 100°C. The metal ammonium chromate was decomposed by heating small portions carefully in a covered dish. The resulting chromite was heated for an hour in a crucible furnace. Nickel chromite No. 1, copper chromite No. 1, cobalt chromite KO. 1, and zinc chromite No. 1 were leached with hydrochloric acid until the excess metal oxide was dissolved out.
Cobaltites Holgersson and his, coworkers (17) report the formation of cobaltites, n/ICo204,when a divalent metal nitrate and cobalt nitrate in a 1:2 mole ratio are dissolved in water, evaporated, the nitrates decomposed, and the resulting mixture of oxides heated to 80O-85O0C. for a few hours. Natta and his coworkers (26,27) have examined the structure of these compounds by means of the x-ray. They found them to be spinel-type compounds with a general formula M++O.1’L+++O3. Iron cobaltite No. 2 and zinc cobaltite No. 2 were prepared by Holgersson’s method. The others were prepared by dissolving the nitrates in a 2: 1 mole ratio of cobalt and the other metal in water, adding a sufficient excess of ammonia to dissolve nearly all the original precipitate and form the ammonia complex (in the case of iron, naturally only the cobalt dissolved and formed the ammonia complex), evaporating the solution to dryness, decomposing the residue, and finally heating in the crucible furnace. This method gave a more finely divided, and to some extent more active, catalyst than the evaporation of the nitrates.
Ferrites S. Hilpert (15) and Suzanne Veil (30) report the formation of ferrites by heating the mixed oxides to 900°C. Natta and Passerini ( 2 5 ) and Holgersson (16) have studied the crystal structure by means of x-rays and have found spinel forms. Cobalt ferrite No. 1, copper ferrite No. 1, nickel ferrite No. 1, and manganese ferrite No. 1 were prepared by dissolving the nitrates of iron and the other metal in a 2 : 1 mole ratio in water, evaporating to dryness, decornposing the nitrates by heating, and finally heating the mixed oxides to the desired temperature. The ferrites No. 2 were prepared by precipitating the hydroxides from a solution of the nitrates or chlorides in a 2: 1 mole ratio. The resulting hydroxides were filtered, washed with hot water, dried, and heated in the crucible furnace. Cobalt ferrite No. 2-B was washed with hot water after the final heating until the filtrate showed no test for chlorides, then heated again to 975’C.
CATALYSTS FOR CARBON MONOXIDE OXIDATION
737
Manganites Cobalt manganite No. 2 was prepared according to Gmelin (13). Twenty-one grams of cobalt sulfate and 12 g. of potassium permanganate were dissolved in 600 cc. of water. Six hundred cc. of 3 per cent hydrogen peroxide were then added. The precipitate was filtered, washed free of sulfates, dried, and heated. The copper-cobalt manganite was prepared according to the directions in the patent of the I . G. Farbenindustrie (18). To 500 cc. of a saturated solution of potassium permanganate was added 60 g. of cobalt sulfate and 50 g. of copper sulfate. Hydrogen peroxide was then added until the permanganate color was discharged. The precipitate was filtered, washed free of sulfates, dried, and heated. The copper manganite and cobalt manganite No. 1 were made similarly.
Aluminates The aluminates may be prepared by heating the mixed oxides in the correct mole ratios. Hedrall (14) has prepared many of these and Holgersson (16) and Natta and Passerini (25) report spinel structures from x-ray studies. Most of the aluminates have very distinctive colors. Copper aluminate No. 2 and nickel aluminate No. 2 were prepared from a solution of the nitrates in a 2 : l mole ratio of aluminum and the other metal by adding ammonium hydroxide to a slight excess and precipitating the hydroxides. The mixed hydroxides were filtered off, washed, dried, and heated. The other aluminates were prepared by evaporating the solution of the nitrates to dryness, decomposing the nitrates, and heating. The results of the tests of the efficiency of the unsupported catalysts are summarized in table 1. SUPPORTED CATALYSTS
Aluminum oxide was used as the support. A ready supply was found in Hydralo, a commercial granular and porous product containing some silica. Precipitated alumina was also used. Inasmuch as Hydralo takes up moisture from the air very readily, it was necessary to heat the catalysts and let them cool in a dry atmosphere just before testing. Moisture acted as a poison for these catalysts at moderate temperatures. The supported cobalt catalysts were the same color as cobalt aluminate and apparently consisted of a surface layer of cobalt aluminate on the alumina.
Cobalt aluminate No. 3 To 10 g. of Hydralo was added 6 g. of cobalt nitrate dissolved in 40 cc. of water. The mixture was evaporated to dryness, the nitrates decomposed, and the material heated to 1000°C. for 1 hour.
738
W. H. LOCKWOOD AND J. C. W. FRAZER
TABLE 1 Egiciency of unsupported catalysts IEATED
PER CENT OF CARBON MONOXIDE CONVERTED AT
I HOUR
CATALYST
AT
"c.
j0"C.
__
Cobalt chromite No. 1 . .. . . . . . . . . . . 1000 Copper chromite No. 1 . . . . . . . . . . . . 1000 Nickel chromite No. 1 . .. . . . . . . . . . . 1000 Nickel chromite No. 2 . . . . . . . . . . . . . 700 Zinc chromite No. 1 . . . . . . . . . . . . . . . 725 Zinc chromite No. 2 . . . . . . . . . . . . . . . 725 Mixed copper-cobalt chromite No. 1. 325 Mixed copper-cobalt chromite No. 2. 750
0 0 0
0 0 0 40 15
00°C
50°C
100°C
150°C
300°C
-
-
- __ 0 0 55 100 8 60 100 - 0 0 15 62 100 0 11 45 94 100 73 100 0 8 22 8 25 41 48 65 - - 100 70 100 - - -
-
-
Copper cobaltite No. 1 . . . . . . . . . . . . Nickel cobaltite No. l . ,. . . . . . . . . . . Iron cobaltite No. 1 . . . . . . . . . . . . . . . Iron cobaltite No. 2 . . . . . . . . . . . . . . . Zinc cobaltite No. 1 . . . . . . . . . . . . . . . Zinc cobaltite No. 2 . . . . . . . . . . . . . . .
950 950 925 925 925 925
0 0 0 0 0 0
10 30 8 15 20 10
78 80 50 55 62 60
100 100 100 100 100 100
Cobalt ferrite No. 1 . . . . . . . . . . . . . . . Cobalt ferrite No. 2 - A . . . . . . . . . . . . . Cobalt ferrite No. 2-B.. . . . . . . . . . . . Copper ferrite No. 1 . . . . . . . . . . . . . . . Copper ferrite No. 2 . . . . . . . . . . . . . . . Nickel ferrite No. 1 . . . . . . . . . . . . . . . Manganese ferrite No. 1 . .. . . . . . . . .
975 700 975 975 700 975 975
0 0 0 0
0
0 2 0 0 4 0 0
18 16 21 7 25 4 0
66 50 60 41 68 17 6
Copper cobalt manganite No. 1 . . . . Copper manganite No. 1 . .. . . . . . . . . Cobalt manganite No. 1 . . . . . . . . . . . Cobalt manganite No. 2 . . . . . . . . . . .
1000 1000 1000 1000
0 0 0 0
0 0 0 0
3 78 18 2
12 100 45 7
Cobalt aluminate No. 1 . . . . . . . . . . . . Copper aluminate No. 1 . , . . , , . . , . , Copper aluminate No. 2 . . . . . . . . . . . Manganese aluminate No. 1 . .. . . . . . Nickel aluminate No. 1 . . . . . . . . . . . . Nickel aluminate No. 2 . . . . . . . . . . . . Zinc aluminate No. 1 , .. . . . . . . . . . . . Iron aluminate No. 1 , .. . . . . . . . . . . .
975 975 975 975 975 975 975 975
45 0
70 0 8 0 0 0
0 0
0 0 0 0 0 0
0 0
-
-
-
100 90 100 90 100 87 100 87 100 82 46 15 38 23
-
77 30
42 94 57
- 100 25 100 - 75 100 - 18 62 100 9 58 90 100 18 54 100 0 0 0 0 6 25 70 100 I
8
Cobalt aluminate N o . 4
A fresh layer of alumina was put on the surface of the Hydralo by adding 3 g. of aluminum nitrate in water to 10 g. of Hydralo, evaporating to dryness, and heating to 1000°C. This Hydralo was then treated as above.
CATALYSTS FOR CARBOX MOSOXIGE OXIDATION
739
Cobalt aluminate S o . 5 Sixty-five grams of aluminum sulfate and 1.5 g. of cobalt nitrate were dissolved in 1000 cc. of water and ammonia added until just alkaline. The precipitate was washed, dried, heated to 1000°C. for 1 hour, washed until free from sulfate, heated to 1000°C. again, allowed to stand overnight in an ammoniacal solution of cobalt nitrate, washed until free from ammonia, and finally heated a t 1000°C. for 1 hour. Kleinstuck (19) reported that alumina took up metals from ammoniacal solutions of their salts and on ignition gave characteristic colors. He also mentioned that the blue-green copper compound oxidized warm methyl alcohol. Schenk (28) found that if not more than 5 per cent copper oxide was present in a precipitated mixture of copper and aluminum oxides the resultant mixture was grayish blue on ignition. The copper catalysts prepared were all bluish green in color. If too much copper were put in, they turned broil-n like copper aluminate. The catalyst was apparently a finely divided stabilized copper oxide. Coppel- oxide LVo. 1
Ten grams of Hydralo was put in a solution of 2 g. of copper nitrate in 20 cc. of water. The mixture was evaporated, the nitrates decomposed, and heated to 925°C. for 1 hour. Copper oxide
2
Two grams of aluminum nitrate in 20 cc. of water was added to 10 g. of Hydralo. The solution was evaporated to dryness, nitrates decomposed, and heated to 1000°C. for 1 hour. It was then put into a solution of 2 g. of copper nitrate in 20 cc. of water, evaporated to dryness, nitrates decomposed, and heated to 1000°C. for 1 hour. Copper oxide No. 3 Ten grams of Hydralo \vas treated with a small amount of sodium silicate solution and heated to 1000°C. It was then put in a copper nitrate solution and the solution evaporated to dryness carefully so as not to decompose the nitrates. The residue was washed with water until the wash water showed no copper. The residue was dried and heated to 1000°C. for 1 hour. Copper oxide KO. 4
Ten grams of Hydralo was treated with ammonium hydroxide solution, the ammonia poured off, and immediately aluminum nitrate solution was added. This formed a gelatinous alumina around the Hydralo. This was washed, allowed to stand in copper nitrate solution, then washed until the wash water was free from copper, dried, and heated to 1000°C.
740
W. H. LOCKWOOD AND J. C. W. FRAZER
Copper oxide
No. 5
Ten grams of Hydralo was allowed to stand in aluminum nitrate solution for several minutes and was then transferred into ammonium hydroxide solution. It was treated with an ammoniacal solution of copper nitrate, washed until free from alkali, dried, and heated to 1000°C. Copper oxide No. 6 About 75 g. of anhydrous aluminum chloride was dissolved in 1500 cc. of water. The solution was heated to boiling and ammonia was added until the solution was decidedly alkaline. Then an ammoniacal solution ,
TABLE 2
Eflciency of supported catalysts TEMPERhTURE O B TEST
CATALYST
P E R CENT CONVERBION
degrees C:
Cobalt aluminate No. 3 . . .. . . . . . . . . . . . . . . . . . . . . . . . Cobalt aluminate No. 4... . . . . . . . . . . . . . . . . . . . . . . . . Cobalt, aluminate No. 5 . ,. . . . . . . . . . . . . . . . . . . . . . . . .
157 164 90
75 100 100
Copper oxide No. 1 . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
161 124 154 100 118 26 70 25 55 26 70
50 75 100 90 100 50 100 50 76 50 100
Copper oxide No. 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
i
Copper oxide No. 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Copper oxide No. 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Copper oxide No. 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Copper oxide No. 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
of copper chloride was added until the supernatant liquid was dark blue. The precipitate was washed by decantation until free from alkali, filtered, washed, dried, and heated to 1000°C. for 1 hour. OXIDATION W I T H NITROUS OXIDE
In order to arrive a t some mechanism for the catalytic action of the various catalysts, it was decided to use some other source of oxygen than that of the air. So a 40:60 mixture of nitrous oxide and nitrogen was used with 1 per cent carbon monoxide. The temperatures of 100 per cent oxidation in nitrous oxide and in air are given in table 3. It will be noticed that the chromites, cobaltites, and manganites give 100 per cent oxidation at temperatures rather close together, while with
74 1
CATALYSTS FOR CARBON MONOXIDE OXIDATION
the aluminate and the copper oxide there is a wide discrepancy. In the first class are those compounds whose metal anion has a variable valence while in the other no such possibility exists. Lory (24) has shown that with air the chromites form a surface chromate which may be leached off with hot water. The amount of chromate may be determined by adding potassium iodide and titrating the liberated iodine with thiosulfate. Chromate formation was likewise proved here with the nitrous oxide. Five grams of copper chromite No. 1was heated to 300°C. for 2 hours, leached with hot water, and chromate equivalent to 11.5 cc. of 0.01 N thiosulfate was obtained. It was heated again to 300°C. and then put in the nitrous oxide-nitrogen-carbon monoxide gas stream at 193°C.for 3 hours. At the end of that time a test showed 100 per cent oxidation of the carbon monoxide. The chromite was leached and showed st chromate equivalent of 5.8 cc. of thiosulfate. It was dried at 90°C. and then leached, showing a TABLE 3 Compamkon of oxidation with nitrous oxids and air* T E M P E R A T U R E AT 100 P E R CENT OXIDATION
CATALYST
Copper chromite No. 1. . . . . . . . . . . . . . . . . . . . . . . . . . Cobalt chromite No. 1 . .. . . . . . . . . . . . . . . . . . . . . . . . . Copper cobaltite No. 1 . . . . . . . . . . . . . . . . . . . . . . . . . . Copper manganite No. I . . . . . . . . . . . . . . . . . . . . . . . . Cobalt aluminate No. 1. . . . . . . . . . . . . . . . . . . . . . . . . . ?Copper oxide No. 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
-I
'I
198 I56 25
185 170 250
* Mr. C. G. Albert made the tests with nitrous oxide.
t 50 per cent
oxidation.
chromate equivalent of 0.8 cc. of thiosulfate. It was dried again a t 90°C. and put in the train as before. After 4 hours in the gas stream at 196°C. the catalyst showed 100 per cent conversion. It was removed and leached and showed 2.2 cc. thiosulfate or nearly three times the amount of the blank (0.8 cc.). This indicates that the nitrous oxide oxidizes the chromite analogously to air, but not quite all the surface is oxidized,-only the more active spots and apparently these are the catalytically active spots. While the carbon monoxide is capable of reducing the whole surface, only the more active parts are oxidized by nitrous oxide and serve for catalysis. This serves to bear out further Lory's theory of alternate oxidation and reduction of the catalyst surface. REACTIONS
OF COPPER OXIDE NO.
6
Some copper oxide No. 6 was put in a tube between two gas burets and heated to 370°C. Nitrous oxide was passed back and forth over it without
742
W. H. LOCKWOOD AND J. C. SV. FRAZER
any change in volume. Apparently it does not act as a catalyst for the dissociation of nitrous oxide. The fact that there is no free oxygen present in the nitrous oxide oxidation helps to account for the difference in temperature of equivalent conversions. Hydrogen was passed over the catalyst a t 175°C. Brownish copper-
FIQ.1. ADSORPTIONOF OXYGENON COPPEROXIDE No. 6
colored spots appeared on the catalyst a t different places and the spots gradually spread out until the whole catalyst was copper colored. On exposure to the air the catalyst slowly turned ta its original bluish green with a distinct evolution of heat. The catalytic activity was the same a t the end of the experiment. This indicated that the copper oxide was so finely divided that the reduced copper was almost pyrophoric.
CATALYSTS FOR CARBON MONOXIDE OXIDATIOX
743
Pure carbon monoxide was passed over the catalyst for 1.5 hours a t 22OoC., but no reduction mas discernible, while hydrogen reduced the same catalyst completely in 10 minutes. Evidently an oxidation-reduction mechanism could not be used to explain the catalysis. The adsorptive capacity of the catalyst for oxygen and for carbon monox-
FIG. 2. ADSORPTION OF CARBON MONOXIDE ON COPPEROXIDENo. 6
idc was then determined. The adsorptions were made in the customary way. A mercury vapor pump was used to evacuate the apparatus to lob5 em. or better. The catalyst was degassed at 375°C. overnight after each run. The gases were purified by standard methods. The dead space in the apparatus was determined with helium. The sample of supported copper oxide weighed 6.33 g. and the dead space was 10.9:cc.
744
W. H. LOCKWOOD AND J. C . W. FRAZER
The oxygen adsorption at all temperatures and pressures was instantaneous. The carbm monoxide adsorption was instantaneous at - 79”C., but a t 0°C. and room temperature there was an immediate adsorption followed by a slower adsorption which lasted from half an hour to four hours. The pressure decrease was rapid a t first and then became progressively slower. This is indicative of chemical adsorption. The adsorption isotherms are shown in figures 1 and 2. The volume is calculated to standard conditions. They agree qualitatively with Benton’s (4) adsorptions on copper oxide but show a larger adsorption, as would be expected from the more finely divided copper oxide. Adsorption measurements of oxygen, carbon monoxide, and carbon dioxide on copper chromite and other of the catalysts are now being made in this laboratory. DISCUSSION OF RESULTS
From the standpoint of efficiency the supported copper oxide catalysts are by far the best of those reported, although several others give good conversion of carbon monoxide at moderate temperatures. From the standpoint of the mechanism of the reaction it is possible to divide the catalysts into two groups,-those with a probable oxidationreduction mechanism and those which probably do not have such a mechanism. The chromites, cobaltites, ferrites, and manganites may be put in the former class, while the aluminates and the supported copper oxides belong in the latter. It has been shown by Lory, and further substantiated by the present work, that there is a formation 3f surface chromate on the chromites and that this is reduced by carbon monoxide and oxidized by air and also nitrous oxide. These reactions indicate that the catalytic action is due to an alternate oxidation and reduction of the surface layer. The adsorption measurements being made here should throw further light on this. On the other hand it appears that carbon monoxide will not reduce the copper oxide catalysts, and with the aluminates there is no possibility of valence change similar to that occurring with the chromites. The adsorption measurements show that carbon monoxide is chemically adsorbed on the surface of the copper oxide and also adsorbed very strongly, while the oxygen is adsorbed only slightly. Bone and Andrew (6) say that on ordinary copper oxide a layer of oxygen and nitrogen is adsorbed, that theoxygen is “activated,” and that this oxygen oxidizes the carbon monoxide. However from the measurements made here it would seem that the carbon monoxide was the more strongly adsorbed and received an energy of activation due to adsorption and then reacted with the oxygen somewhat similarly to Langmuir’s (21) explanation of the action of platinum on this same reaction.
CATALYSTS FOR CARBON MONOXIDE OXIDATION
745
SUMMARY
1. Methods of preparation and tests of eight chromite, six cobaltite, seven ferrite, four manganite, eleven aluminate, and six supported copper oxide catalysts have been given. 2. Further evidence has been adranced to show that the mechanism of the chromite catalysis is alternate oxidation and reduction. 3. The adsorption isotherms for oxygen and for carbon monoxide on a supported copper oxide catalyst a t -79"C., O'C., and 27°C. have been determined. 4. A mechanism for the catalytic action of the supported copper oxide catalysts has been proposed. REFERENCES ADKINSAND CONNOR: J. Am. Chem. SOC.63, 1091 (1931). ALMQUISTA N D BRAY:J. Am. Chem. SOC.46,2305 (1923). BENNETT, 0. G. : Dissertation, Johns Hopkins University, 1930. BENTON:J. Am. Chem. SOC.46, 887 (1923). BENTON:J. Am. Chem. SOC.46, 900 (1923). BONEA N D ANDREW:Proc. Roy. SOC.London llOA, 16 (1926). BRAYAND Doss: J. Am. Chem. SOC.48, 2060 (1926). CONNOR, FOKLERS, AA-D ADKINS:J. Am. Chem. SOC.64, 1138 (1932). ENGELDER AND BLUMER: J. Phys. Chem. 36, 1353 (1932). A N D MILLER: J. Phys. Chem. 36, 1345 (1932). ENGELDER FRAZER: G. S. patent 1,789,812, January 20, 1931. FRAZER:J. Phys. Chem. 36, 405 (1931). GMELIN'S Handbuch der anorganischen Chemie, Vol. V, 1, 1215. Z. anorg. allgem. Chem. 96,71 (1916); 103,249 (1918); 116, 137 (1921). HEDVALL: HILPERT:Ber. 42, 2248 (1909). I~OLQERSSOA-: Kgl. Fysiogr. Sellk Hand. N. F. 38, 1 (1929); Chem. iibstracts 24, 804. (17) HOLQERSSOAA N D KARLSON: 2. anorg. allgem. Chem. 183,384 (1929). (18) I. G. Farbenindustrie Aktiengesellschaft, French patent 704,119, February 17, 1931. (19) KLEINSTUCK: Z. angew. Chem. 23, 1105 (1910). Ind. Eng. Chem. 12, 213 (1920). (20) LAMB,BRAY,AXD FRAZER: (21) LASGMUIR:Trans. Faraday SOC.17, 621 (1922). (22) LAZIER:U.S. patent 1,746,783, February 11, 1930; British patent 301,806, June 12, 1926. (23) LOANE:J. Phys. Chem. 37, 615 (1933). (24) LORY:J. Phys. Chem. 37, 685 (1933). (25) NATTAA N D PASSERINI: Gam. chim. ital. 69,280,620 (1929). (26) NATTAAND PASSERINI: Gazz. chim. ital. 69,620 (1929). (27) NATTAA N D STRADA: Atti accad. Lincei 7, 1024 (1928). (28) SCHENK:J. Phys. Chem. 23, 283 (1919). (29) TAYLOR AA-D JONES:J. Phys. Chem. 27, 623 (1923). (30) VEIL, S.: Compt. rend. 188,330 (1929). (31) WHITESELL A N D FRAZER: J. Am. Chem. SOC.46, 2841 (1923). (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16)
