968
T H E J O U R N A L O F I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y 1701.
sample. During this procedure, stopcock i is turned t o permit the evaporating liquid air t o escape into t h e atmosphere. Since t h e apparatus must be cleared with fresh air and t h e determination is being made in the gas t o be tested, stopcocks i and h are now turned t o place t h e liquid air chamber in communication with f and t h e tube thus filled with “pure air’’ for sweeping the train. The apparatus is contained in a cabinet 24 in. X 2 0 in. X 7 in. A determination should take about I j min. and should be accurate t o from 0.003 t o 0.005 per cent carbon monoxide (0.3 t o 0.5 part in 10,000). SUMMARY
The iodine pentoxide method for determining low concentrations of carbon monoxide has been investigated with reference t o its use with dilute motor exhaust gas. The type of apparatus heretofore used was found t o give appreciably high results owing t o the presence of small amounts of unburned gasoline. A new iodine pentoxide apparatus (Type 11) has therefore been developed. All of the interfering gases are first removed a t t h e temperature of liquid air. This method has been found quite satisfactory for determining carbon monoxide in small quantities in the presence of gasoline vapor. A portable iodine pentoxide apparatus has been designed which should permit a determination t o be made in I 5 min. with an accuracy of from 0.003 t o 0.00 j per cent carbon monoxide (0.3 t o 0.5 part in 10,000). ACKKO WLEDGMENT
Appreciation is expressed t o Dr. A. C. Fieldner, supervising chemist in charge of tunnel gases investigation, and Dr. Yandell Henderson, in charge of physiological investigations, for valuable suggestions and advice, and t o Mr. W. B. Fulton for making many of the determinations herein reported. THE USE OF CATALYSTS IN T H E SULFONATION OF AROMATIC COMPOUNDS By Joseph A. Ambler and William J. Cotton COLORLABORATORY, U. S. BUR$AUOF
CHEMISTRY, WASHINGTON,
D.
c.
Received May 12, 1920
During the course of experimentation on the vaporphase sulfonation of compounds, i t was found t h a t by using the continuous method of Ambler and Gibbs,l with a given set-up of apparatus and given temperature range, t h e amount of material sulfonated per minute was practically constant; that is, the apparatus had a certain “capacity” for sulfonation, since so long as t h e baffies in the apparatus were not disturbed, the free space for vapors and t h e absorbing or sulfonating surface were constant. The method, therefore, provided a good means of studying the effect of various substances introduced with the reacting materials, and of ascertaining which were catalyzers of the sulfonation reaction. This work is intended as introductory t o a much more complete study of sulfonation catalysts. Inasmuch as t h e study will be unavoidably 1 U. S. Patents 1,292,950; 1,300,227; 1,300,228. this process will be published in subsequent papers.
A description of
12,
NO. T O
delayed for some time, i t seems best t o publish t h e work thus far accomplished, although it is incomplete. Various workers have reported t h a t t h e sulfonation of aromatic compounds m+y be accelerated by adding different catalysts. T h e addition of sodium sulfate] or various acid sodium sulfates2 has long been common practice, and a similar use of potassium sulfate3 has also been reported. It is also well known t h a t various sulfonic acids can easily be further sulfonated in t h e form of their sodium or potassium salts; whereas, if t h e free acid is used, t h e introduction of more sulfonic acid groups becomes extremely difficult, as, for example, in t h e production of benzene-~,g, j-trisulfonic acid4 from t h e salts of benzene disulfonic acid. I n all of these cases, t h e large amount of the alkali salts used makes it almost impossible t o decide whether the action is catalytic, or caused by t h e greatly increased boiling point of t h e sulfuric acid-alkali sulfate mixture used. Other substances recommended as accelerating catalysts are vanadium6 in t h e sulfonation of anthraquinone, and iodine6 in t h e sulfonation of benzene. Compounds of mercury, aluminium, iron, lead, arsenic, bismuth, cadmium, and manganese7 have also been studied from the standpoint of their effect upon the position in the molecule taken by the entering sulfonic acid group. EXPERIMENTAL DETAILS
I n t h e present work some of t h e compounds mentioned above have been studied t o ascertain whether they exert any accelerating (catalytic) effect on t h e sulfonation of benzene, and all so far examined have shown some catalytic action. These substances are copper sulfate, mercuric sulfate, vanadium pentoxide, sodium sulfate, chromic acid, potassium sulfate, lithium sulfate, and mixtures of sodium sulfate an& vanadium pentoxide. I n every case the substance was dissolved in 7 0 per cent sulfuric acid, thus insuring a constant concentration of the catalyst in the reaction tower. The concentration of catalyst is expressed as the percentage of the characteristic element, although in making t h e solutions t h e above-mentioned compounds were actually added t o t h e sulfuric acid. For example, 0.1 per cent copper means t h a t t h e amount of copper sulfate used was chemically equivalent t o t h a t weight of copper which was 0.1 per cent of the weight of the sulfuric acid. I n each case t h e experiment was carried on for from a n hour t o an hour and a half, after which time t h e products of t h e reaction were discarded, a t t h e same time “cutting in” with weighed quantities of acid and benzene. The experiment was considered as starting 1 Girard, Bull. soc. chim., 26 (1876), 333; Miihlhauser, Dinglev’s polytech. 1,.263 (1887), 154. 2 Lambert, D. R. P. 113,784 (1899); Kendall, U. S. Patent 1,217,462
(191 7). 8 Jackson and Wing, Am. Chem. J., 9 (1887), 325. 4 Jackson and Wing, LOC. cit.; Behrend and Murtelsmann, Ann., 378 (1911), 352. 6 Thummber, D. R. P. 214,156 (1909). 5 Hinemann, Brit, Patent 12,260 (1915). 7 Iljinsky, Ber., 36 (1903), 4194; Schmidt, Ibid., 37 (1904), 66; Dunschmann, Ibid., 37 (1904), 331; Holdermann, Ibid., 39 (1906), 1250; Dimrotb and Schmaedel, Ibid., 40 (1907), 2411; Behrend and Mertelsmann, LOG. c i t . ; Mohrmann, Ann., 410 (1915), 373.
Oct.,
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
I920
from this point in order t o be sure t h a t the reaction had become thoroughly established and t h a t everything about the apparatus was in a state of equilibrium which could be maintained until the end of the experiment; and t o obviate the large error inherent in the apparatus, due t o the fact t h a t i t took some time for the benzene vapors t o displace all the air in the apparatus, and for the sulfuric acid t o wet all the surfaces of the baffles and the walls of the tower, during which time the apparatus did not operate a t its maximum capacity. TABLEI
Catalyst
...
Con c en tration Per cent
...
c u . . . . . . . . . . 0.1 Hg.. . . . . . . . . 0.1 v . . . . . . . . . . . 0.1 Na(1) . . . . . . . 0 . 1 Cr.. . . . . . . . . . 0.1 K . . . . . . . . . . . 0.17 L i . . . . . . . . . . . 0.094 Na(I1) . . . . . . 0 . 5 Nn(II1) ...... 0 . 1 N a . ,. , , , , , . , 0.1 V . .’.. , , . , , , 0.05 V . , . . . . . . . . . 0.223 Na. . . . . . . . . 0.025}
1
.
Mean Temp. C. 243 25 1 243 249 252 249 257 246 255 259 242
’
Wt. W t Benzene Duration Sulfonic Sulfonated per Min. of Expt. Acids Min. Grams Grams 580 734 0.63 185 301 0.80 232 386 0.82 249 356 0.71 291 649 1.10 202 278 0.67 292 479 0.82 283 405 0.61 300 492 0.83 355 601 0.84 274 626 1.13 232
249
592
1.26
Tables I and I1 give the critical data so far as the catalysts are concerned. The “weight of sulfonic acids” in Table I was found as follows: Total acidity, expressed in terms of sulfuric acid, was determined by titration with standard alkali, using phenolphthalein or thymolsulfophthalein for indicator. Actual sulfuric acid was determined with barium chloride as usual. The difference of these two determinations represented sulfuric acid equivalent t o the sulfonic acid present. The latter was temporarily assumed t o be benzene monosulfonic acid, and its amount : zHSO3.CeH6. calculated according t o the ratio From this value i t was a simple matter t o calculate the amount of benzene sulfonated per minute. TABLE I1
..
........... ........... v ............ Cr ............ Li ............ Na(I1) ....... Na(II1) ....... Na. . . . . . . . . . . v............ cu Hg
v............ Na.
..........
...
0.1 0.1 0.1 0.1 0.094 0.5 0.1
0 223 0:025
243 251 243 249 249 246 255 259 242
580 185 232 249 202 283 300 356 274
705 294 377 355 274 380 463 574 595
147 28 36 6 13 95 111 101 121
0.56 0.76 0.78 0.66 0.66 0.61 0.70 0.75 1.00
0.25 0.15 0.16 0.03 0.06 0.34 0.37 0.29 0.44
249
232
569
88
1.15
0.39
These figures, however, were subject t o error, inasmuch as some benzene disulfonic acid was always formed. Table I1 contains corrected values, based on the following calculation: The amount of disulfonic acid was determined by analysis of the barium salt of the sulfonic acids, making necessary corrections for the catalyst itself when i t was found in the barium salt. The weight of sulfonic acids was then corrected and, by using the t’wo ratios C&s : CsHsS03H and CsH,; : C&(S03H)2, the amount of benzene actually sulfonated per minute was calculated.
969
It should be noted here t h a t two experiments given in Table I do not appear in the second, viz., Na(1) and K. Through a n unfortunate oversight the amount of benzene disulfonic acid was not correctly determined, because no determination of the amount of catalyst contained in the barium salt was made. The experiment with no catalyst is typical of many in which the amount of benzene sulfonated per minute was always approximately 0.5 g. This figure represents the normal capacity of the apparatus. DISCUSSION O F R E S U L T S
A study of Table I shows t h a t all the substances used increased the amount of benzene sulfonated per minute, a n d t h a t these catalysts are divided into two general groups, viz., those which have a slight catalytic action, copper, mercury, vanadium, chromium, potassium, lithium, and two of the experiments with sodium; and those which have a marked catalytic action, the first experiment with sodium, and the two experiments using both sodium and vanadium. The more marked effect in the first experiment with sodium was caused by a small amount of vanadium, which had been used in the experiment just preceding i t , and which had not been completely removed from the tower. The most active catalyzer is obviously a mixture of sodium and vanadium in any reasonable proportion. The results also clearly show t h a t the sodium and potassium sulfates in sulfonation mixtures have a distinct catalytic effect, and t h a t the advantages gained by their use are not entirely due t o the increased boiling point of the sulfuric acid. Another interesting fact brought out is the effect of the catalyst on the amount of disulfonic acid formed per minute. This subject is t o be investigated further. Apparently the members of the first group of t h e periodic system, represented here by sodium and lithium, accelerate the formation of disulfonic acid in this type of sulfonation, while the mixture of vanadium pentoxide d i t h sodium sulfate is still more effective. The other catalysts apparently inhibit t h e formation of disulfonic acid. PHTHALIC ANHYDRIDE. IV-THE VAPOR PRESSURE O F PHTHALIC ANHYDRIDE By K. P. Monroe COLORLABORATORY, U. S. BUREAUon CHEMISTRY, WASHINGTON, D. C. Rec:ived June 1, 1920
The investigation of the vapor-pressure curve of phthalic anhydride was initiated t o assist in the solution of certain problems arising in the air-oxidation process recently developed by Gibbsl and his coworkers. Although the results were obtained in a preliminary series of measurements, and are not of the order of accuracy which i t was hoped t o obtain by repetition with a more refined mercury gage, they are presented, since i t appears unlikely t h a t the author will resume the investigation. Phthalic anhydride, purified by a method previously described,2 was placed in a static isoteniscope of the 1 See the previous articles of this series: “Phthalic Anhydride,” I, by H. D Gibbs, THIS JOURNAL, 11 (1919), 1031, “Phthalic Anhydride,” I1 and 111, by K P Monroe, I b i d . , 11 (1919). 1116 and 1119 1 Part 11, LOC.cit.
