MARCH 15, 1938
-4NALYTICAL EDITION
vestigation was carried on, for his interest and helpful suggestions and to thank him for the privilege of using the Purdue spectrophotometer. Thanks are also given to W. B. Fortune of Purdue for his profitable criticism and for preparing standard solutions of ions and adjusting the spectrophotometer.
Literature Cited (1) Agnew, W. J., Analyst, 53, 30 (1928). (2) Beoh, P. F., Dansk Tids. Farm., 9,289 (1935). (3) Gregory, A. W., J. Chem. SOC.Trans., 93, 93 (1908); Chem. Soc., 23, 263 (1907).
Proc.
(4) Mellon, M. G., “Methods of Quantitative Analysis,” p. 413, New York, Macmillan Co., 1937. ENG.CHEM.,Anal. Ed., (5) Mellon. M. G.. and Kasline. C. T.. IND. 7, 187 (1935).
139
(6) Michaelson and Liebhafsky, Gen. Elec. Rev., 39, 446 (1936). (7) Pagliani, S., J. Chem. Soc., 36, 748 (1879). (8) Sagaidachnuii, A., and Ravich, M., J. Rziss. Phys. Chem. Soc., 58, 1018 (1926). (9) Smith, E. F., Proc. Am. Phil.Soc., 18, 214 (1880). (10) Snell, F. D. and C. T., “Colorimetric Methods of Analysis.’’ p. 301, New York, D. Van Nostrand Co., 1936. (11) Steenkamp, J. L., J. S.African Chem. Znst., 13, 64 (1930). (12) Swank, H. W., and Mellon, M. G., IND. ENG.CHEM.,Anal. Ed. 9,406 (1937). (13) Vogel, A., N . Rept. Pharm., 25,180 (1876); Chem. Zentr., p. 375 118761. -,\ - - .
(14) Wright, E. R., and Mellon, M. G.. ISD.ENG.CHEM.,Anal. Ed.,
9, 251, 375 (1937). (15) P o e , J. H., “Photometric Chemical Analysis,” Vol. I, p. 243. New York, John Wiley & Sons, 1928.
RECEITED December 3, 1937.
Platinized Silica Gel as a Catalyst for Gas Analysis U’
Complete Oxidation of Methane and Ethane KENNETH A. KOBE
AND
WALTER I. BARNET, University of Washington, Seattle, Wash.
I
T HAS been shown (2) that hydrogen can be quantita-
tively oxidized by adding oxygen to the hydrogen-hydrocarbon residue remaining after carbon monoxide absorption and passing the gas over platinized silica at 100” C. The copper oxide tube was replaced by a catalyst tube similar in design, containing 1 gram of a commercial platinized silica gel. Complete oxidation of carbon monoxide did not occur at temperatures below 300” C. At this temperature (3) oxidation of ethane and higher hydrocarbons occurred to a slight extent; so the absorption method for carbon monoxide was recommended when the catalyst-tube method was used in the presence of higher hydrocarbons. LUD ETHASE TABLEI. OXIDATIOKOF METHAKE r
.\nalysis T e m p . , C. S o . of passes R a t e , ml. per minute 0 2 i n analyzed mixture, 7’ CHp by explosion, % CH, b y catalwt, %
\[ethane
Ethane 7 8 620 615 3 3
1 65.5 4
2 610 4
3 610 4
4 565
15
5 610 4
6 610 3
50
50
i5
50
75
75
65
30
30
30
30
50
65
30 t o 35
65
12.5
12.5
12.5
12.5
8.8
6.2CrHs
6.5
6.6
12.5
12.4
12.4
11.8
8.7
6 . 2 C Z H E 6.5
6.6
The latter study (3) was to determine the lowest temperature at which any oxidation of the hydrocarbon occurred; no work was done to determine whether the oxidation of the hydrocarbons could be made complete. If oxidation of the methane hydrocarbons could be made complete a t some temperature, the catalyst-tube method could be used for both hydrogen and hydrocarbons by simply raising the temperature after hydrogen oxidation. The results of such a study are reported in this paper.
by a heating element for a coal volatile-matter furnace. This gave a heating chamber 15 X 3.75 cm. (6 X 1.5 inches) and could attain a temperature of 950’ C. The heater was connected in series with a variable-plate resistance by which the temperature could be controlled. Temperature was measured with a mercurial thermometer (Palo-Myers No. 8006F., range 280’ t o 650” C. in 1’ C.) which was placed within the heater in the usual manner for the hydrogen determination. The methane and ethane were obtained in cylinders from the Ohio Chemical Company.
Oxidation of Methane and Ethane The previous work showed that the oxidation of ethane and higher hydrocarbons began at temperatures considerably below that for methane. If complete methane oxidation can be secured, i t may be concluded that oxidation of the higher hydrocarbons will also be complete. A stock mixture of methane or ethane, oxygen, and nitrogen was made and samples of this gas were diluted with oxygen to give a volume of approximately 100 ml. for analysis. Methane was determined by the explosion and catalyst-tube methods for each sample. The gas mas passed from the buret through the catalyst tube to the explosion pipet and back to the buret again through the catalyst. This double passage through the-catalyst iscalled a pass in Tables I and 11. TABLE 11. OXIDATIOXOF HYDROGEN AXD METHANE Analyzis Temperature, C. Number of passes R a t e , ml. per minute CHI,
%
By explosion By catalyst Hz, 70 By explosion By catalyst
1
2
3
4
610 6 50
G10
620 3 15
620 3
2
15
25
13 0 13.1
6.3
6.5
5.8 5.9
5.8 5.9
21.7 21.6
11.9 11.5
9.Q 10.1
9 9 9.7
Apparatus and Gases The apparatus was that used in the previous work, except that the copper oxide tube was replaced by a similar Pyrex tube containing 1 gram of the commercial platinized silica gel containing 0.075 per cent of platinum produced by the Silica Gel Corporation. The limiting temperature of the standard heater is 400’ C., at which temperature methane is only partially oxidized. The heating element was removed from the steel shell and replaced
The minimum temperature for the complete oxidation of methane was determined and the effect of excess oxygen studied. The results are given in Table I. A temperature of 610” C. is necessary, for analysis 4 at 565’ C. shows incomplete oxidation after 15 passes through the catalyst. As long as a small excess of oxygen remains,
INDUSTRIAL AKD ENGINEERING CHEMISTRY
140
VOL. 10, NO. 3
Oxidation of Hydrogen and Methane
ane. The recommended procedure is to absorb all possible components of the gas mixture, including carbon monoxide, and determine hydrogen and hydrocarbons over the catalyst a t 610" C. As carbon monoxide is oxidized a t 300" C., carbon monoxide, hydrogen, and methane may be
From the volume decrease and carbon dioxide the hydrogen
Conclusions
complete oxidation is obtained. However, larger percentages of excess oxygen permit faster passage of the gas through the catalyst tube.
Discussion
Literature Cited
Methane and ethanearecompletelyoxidizedovercommercial pl.ttinized silica gel a t 610" C. It may be assumed that higher hydrocarbons are also completely oxidized, as previous work ( 3 ) shows that they are more readily oxidized than meth-
(1)
Kobe, K. .4.,ISD. EKG.CREM., Anal. Ed., 3, 262-4
(1931)
(2) Kobe, K. A., and h v e s o n , E. J., I b i d . , 5, 110-12 (1933). (3) Kobe, K. A.2 andBrOokbank9 E. E., Ibid., 6, 35-7 (1934).
RECEIYED December IO, 1937.
Determination of Unsaturation in Organic Compounds By Means of the Mercury-Catalyzed Reaction with Standard Bromate-Bromide HOWARD J. LUCAS
AND
DAVID PRESSIIAN, California Institute of Technology, Pasadena, Calif.
I
T HAS been known for a long time that the reaction of bromine with compounds having a triple bond does not go to completion rapidly. I n the case of acetylene, Davis, Crandall, and Higbie ( 2 ) showed that the slowness and incompleteness of the reaction is due t o t'he presence of oxygen, and that the reaction is aided by aluminum, mercury, and nickel salts. h'lulliken and Wakeman (8) found that in general liquid alkynes and alkadienes do not react quantitatively with standard bromate-bromide solution. Recently (4) the analysis of acetylene in aqueous solution has been carried out quantitatively in the presence of mercuric sulfate, and without taking precautions against oxygen. I n the attempt to develop a method for determining unsaturation, a study has been made of the behavior of bromate-bromide solution, in the presence and in the absence of mercuric sulfate, F i t h a number of unsaturated compounds, some having a triple and some a double bond.
Materials c. P. glacial acetic acid was used in addition to the reagents previously described (4). Carbon tetrachloride was purified by saturating with chlorine, exposing t o direct sunlight for 10 to 12 hours, washing with aqueous sodium hydroxide, and drying with calcium chloride. I t distilled at 75.6" C. uncorrected. Several unsaturated ccmpounds were prepared for this work. The following were used after purification: dichloroethylene (Eastman's), distilled once; maleic acid (Pfanstiehl); fumaric acid (Eastman's) ; and cinnamic acid, crystallized twice.
had about two milliequivalents of unsaturation. Hydrocarbons and water-insoluble compounds were dissolved in carbon tetrachloride as follows: A sealed ampoule of the substance, having approximately 60 milliequivalents of unsaturation, is placed in a weighed, glassstoppered bottle of 150-ml. capacity and rather wide mouth. Some carbon tetrachloride is added, the ampoule is broken, and the bottle is filled with the solvent so that there is only a small air space, tightly stoppered, weighed, and shaken. From the weights of the two liquids, the density of the carbon tetrachloride at the temperature of pipetting and the approximate density of the solute, a volume of the solution, and likewise a concentration of the solute can be calculated, assuming additivity of volumes (perfect solution). By fitting the bottle with a two-hole rubber stopper carrying a separatory funnel (stem reaching to the bottom) and a tube through which a pipet can be inserted, a sample can be forced into the pipet by allowing mercury to flow from the separatory funnel. There should be a sniall air space between the liquid and the stcpper to prevent direct contact, but it should be small, to minimize errors due to dderence in volatility of solvent and solute. The pipet, with a three-way stopcock, is calibrated to contain a definite volume ( 3 ) . The stopcock is lubricated with a water-soluble grease. With a pipet holding 5.6 ml., and with the solution about 0.42 N in unsaturation, the sample delivered has about two milliequivalents of unsaturation. This procedure permits the removal of successive portions of the solution without any change in concentration.
Analytical Procedure
Preparation of Solutions for Analysis
The analytical procedure is based upon that described by Frieman, Kennedy, and Lucas (4).
Aqueous solutions of water-soluble compounds were made hy weighing sufficient material directly into a volumetric flask so that, when made to volume, the liquid was approximately 0.08 N in unsaturation and the sample taken, 25 ml.,
A calculated excess (10 to 15 per cent) of 0.1 N bromatebromide solution (about 25 ml.) is run from a buret into a 300ml. conical flask having a ground-glass stopper bearing a sealed-in stopcock. (The first analysis of the solution is approximate only, and should be carried out with a larger excess of bromate-bro-
