Determination of Sulfur and Chlorine in Gasoline CHARLESWIRTHI11 AND M. J. STROSS Research and Development Laboratories, Universal Oil Products Company, Chicago, Ill.
V
A R I O U S m e t h o d s of treating gasoline through the use of chlorides or other soluble salts of zinc, mercury, iron, copper, and other metals allow the possible chlorination of some of the hydrocarbons. A determination of sulfur in the treated products by the
~ , - ~ $~~~~~i~~~ * ~ i
A laboratory method has been developed for the determination of chlorine and sulfur in gasolines. The procedure is simple and does not demand a n y unusual apparatus or special technic. are Obtained !lasolines containing added quantities of several types of chlorohydrocarbons in the presence of various quantities of compounds, A variation in the type of chlorine compound present in the ~ ~ ~ ~ gasoline does not affect the accuracy Of the determination. A comparison of this procedure with a modiJication of the oxygen bomb method to include the determination of chlorine yields concordant
in excess of that due to the sulfur content, as the chlorine will go over as hydrogen chloride alone. The apparent Sulfur Will therefore be in Of the actual sulfur value. Under such circumstances, there is a need for a simple analytical procedure to determine the sulfur and chlorine contents of the gasoline. Several methods (1, 3, 6, 8) for the determination of sulfur and chlorine are available, but in general they are not adapted to rapidity and ease of manipulation in control work. The bomb methods (3) consist essentially of oxidizing a weighed sample in a bomb with determination of the sulfur as the sulfate and subsequent titration with silver nitrate for chlorides (A. S. T. M. method 129-27 and Parr sodium peroxide method). The method of Willard and Thompson (8),based upon oxidation of the sample with fuming sulfuric acid, is very satisfactory for the determination of chlorides. The halogen is distilled into alkaline arsenate and precipitated as silver halide. Metals may be determined in the same solution. The lamp method of Bowman (1) favors the combustion of the wick after burning the samde. This prolongs an analysis and it has been found unnecessary. The method described is adapted to illuminating oils, petroleum naphthas, gasolines, and other volatile motor fuels which can be analyzed by the A. S.T. M. method D-90-26T. A simple and rapid procedure of analysis with a high degree of accuracy is desired. The several possible sulfur methods which suggest themselves as suitable with the necessary modifications to include chlorine are the oxygen bomb method, the sodium peroxide bomb (4), and the A. S. T. M. lamp determination. I n each instance the resulting solution may be analyzed for sulfur and chlorine either gravimetrically or volumetrically. The new analytical procedure consists of three steps: burning the gasoline in the standard A. S. T. M. lamp with absorption of the combustion products in sodium carbonate; determination of the total acidity due to the combustion of the sulfur and chlorine-containing hydrocarbons; and determination of the chlorine content by Mohr's procedure (6). The total acidity is a measure of the sulfur trioxide and hydrochloric acid formed by combustion of the sulfur and chlorine-containing hydrocarbons and is expressed as percentage of sulfur. The chlorine content with a suitable factor as determined by titration is subtracted from the total acidity. The true sulfur percentage is obtained by difference.
PROCEDURE
Weigh 10 to 15 cc. of the gasoline sample for analysis in an Erlerimeyer flask, fit the wicking into the flask, and burn the gasoline according to the detailed A. S . T. M. procedure. However, do not use hydrochloric acid in t h e t i t r a t i o n of the unused sodium carbonate solution as is c u s t o m a r y in the sulfur determinations, but substitute 0.0623 N sulfuric acid with methyl orange as an indicator. Remove the neutralized solution from the tower with suitable washing and filter it, if necessary, to separate any suspended carbon. Evaporate the filtered solution to approximately 25 to 35 cc. After cooling, add a few drops of a saturated potassium chromate solution. Titrate the solution with 0.1 N silver nitrate solution to the appearance of a red coloration. Dichlorofluorescein ( 2 ) was tried as an indicator in this titration but was not satisfactory in the presence of the methyl orange. The color change of the potassium chromate indicator is more pronounced. The end point as obtained by the sulfuric acid titration indicates the total acidity or the acidity due to the sulfur plus that due to the chlorine content of the sample, Therefore the percentage of chlorine is given by
% chlorine
=
CC.
0.100 N AgNOa X 100 X 0.00355
grams sample burned
u
85
The sulfur content is obtained by difference, chlorine %sulfur = %total acidity = % ___ 2.22
where 2.22 is the factor for converting sulfur to chlorine and total acidity is expressed in terms of percentage of sulfur.
OUTLINEOF WORK The method was tested out by obtaining data upon gasolines of known sulfur and chlorine content. The chlorine content was varied by the addition of known quantities of chlorine derivatives of hydrocarbons, chosen to include several types of chlorinated hydrocarbons. The gasolines used were a naphtha free from chlorine and extremely low in sulfur, and several cracked gasolines containing various percentages of sulfur. The chlorohydrocarbons were added to each type of gasoline in percentages to give chlorine contents as high and as low as likely to be encountered in practical work. The chlorohydrocarbons utilized were: amyl chloride, amylene dichloride, benzyl chloride, butyl chloride, carbon tetrachloride, dichlorobenzene, ethylene chloride, isopropyl chloride, isobutyl chloride, and propyl chloride. Each of these materials was of the highest purity furnished by the Eastman Kodak Company.
Vol. 5, No. 2
ANALYTICAL EDITION
86
TABLEI TOTAL ACIDITY FOUND (SULFUR) CHLORINE 1 2 ADDED CHLOROHYDROCARBON
%
%
%
1
CHLORINE FOUND 2
%
%
LOW-SULFUR AND HIQH-CHLORINE QASOLINE
Gasoline used Benzyl chloride Butyl chloride. Isobutyl chloride Propyl chloride Isopropyl chloride Eth lene chloride Cargon tetrachloride
:
0 346 0.220 0.286 0.269 0.216 0.251 0.307
+0.006
0:263 0.217 0.257 0.300
f0.002 +o. 001 so.011 +0.010 f0.013
o:iQ5 0.140 0.167 0.16’1 0.142 0.157 0.177
0:200
0,’023 0,019 0.022 0.028 0.089 0.059
01063 0.048 0.048 0.051 0.060 0.064
0:054 0:023 0:022 0.017 0,019 0.053 0.025 0.019 0.047 0.023 0.024 0.054 0.035 0.036 0.061 0.056 0.064 0.061 HIQH-SULFUR AND HIQH-CHLORINE QASOLINE
0:090
0 366 0.512 0.443 0.502 0.386 0.450 0.520 0.502
o:iis
0.143 0.154 0.179
LOW-SULFUR A N D LOW-CHLORINE QASOLINE
Gasoline used Amvlene dichloride
Gasoline used n-Amyl chloride Amvlene dichloride Benzyl chloride Isobut 1 chloride o-Dichyorobenzene Erhyletie chloride Fropyl chloride Isopropyl chloride
0.390 0.258 0.232 0.130 0.262 0.361 0.377
...
...
:
...
0:091 0.404 0.265 0.238 0.135 0.272 0.362 0.386
. . ... ... ... . .
... . .
:
0 407 0:236
:
0 277 0.371
...
HIQH-SULFUR AND LOW-CHLORINE QASOLINE
Gasoline used Amylene dichloride B e n ~ y ch1orid.e l Isobutyl chloride Ethylene chloride Propyl chloride Isopropyl chloride Benzyl chloride Benayl chloride Butyl chloride Bury1 chloride Butyl chloride Ethylene chloride Ethvlene cliloride Amylene dichloride Amylene dichloride Amylene dichloride Isobutyl chloride Isobutyl chloride
:
0 033 0.032 0.017 0.037 0.020 0.031 0.031 0.101 0.028 0.076 0.121 0.088 0.221 0.037 0.136 0.261 0.028 0.173
:
0 338 0.350 0.343 0.346 0.339 0.336
... ...
... ... .
.
I
...
... ... ...
... .
.
I
...
:
0 344 0.355 0.337
:...
0 338
:
:
0 033 0.038 0.024 0.038 0.019 0.028
0 035 0.039 0.018
:...
0 023
CHLORINE~ IN THE ABSENCE
... ...
0.035 0.113 0.027 0.077 0.123 0.084 0.228 0.038 0.133 0.265 0.025 0.177
... ... ... ... ... ...
...
...
... ...
o r SULFUR^ 0.037 0.103 0.032 0 : i27 0.083 0.226 0.039 0.140 0:026
0.180
CHLORINATED CRACKED QASOLINE
... ... Gasoline used ... 0:052 Amylene dichloride ... ... 0.080 Benzyl chloride ... 0.099 n-Butyl chloride ... 0.288 Ethylene chloride a A cleaners’ naphtha contrtining 0.005 per cent sulfur was used.
...
0.040 0.094 - 0.040= 0.122 - 0.040 = 0.140 - 0.030 0.324 - 0.040
TABLN11. USE OF CHLORINE CHLORINE FOUND CHLOROHYDROCARBON ADDED BY BOMB ?A % ._ 0.041 Gasoline 0.325 0:329 Ethylene chloride 0.396 0.390 Amvlene dichloride 0.345 0.341 0.267 0.262 0.299 0.294 0.383 0,377 0.036 0.032 0.020
THE
ERROR
.....
-0.004 +0.006
+0.004 +O .005 +0.005 +0.006 +0.004 -0.002
DISCUSSION OF RESULTS The data shown in the accompanying tables cover the analyses conducted upon each “synthetic” chlorinated gasoline. I n Table I the complete range of possible combinations of low and high sulfur and chlorine contents as they would probably occur in gasolines has been investigated. The errors as shown in the table are computed on the basis of the average results of each analysis. The results show that the presence of a range of percentages of chlorine from 0.017 to 0.390 per cent does not affect the accuracy of the sulfur determination upon the samples of sulfur contents from 0.005 to 0.328 per cent. In addition, excellent checks are obtained for the chlorine contents as calculated from the quantity of chlorohydrocarbon added. The chlorine results are apparently not dependent
.....
0 348 0.224
0:3i1 0.214 0.294 0.265 0.206 0.244 0.291
0.147
SULFUR FOUND 1 2
ERROR
0:064 0.082 0.110 0.284
+0.008
.....
0.000 -0.001 0.000 -0.004 -0.003 +o ,001
.....
+0.001 S0.016 +O. 007 +0.005 +0.005 $0.013 +0.006 +0.009
.....
0.041 0.039 0.040 0.038 0.040 0 045 01049 0.033
0.043 0.043 0.045 0.044 0.038 0.043
0.042 0.042 0.040 0.036 0.041 0.040 0.036
0:044 0.044 0.039 0.043 0.043 0.036
0.328 0.315 0.329 0.323 0,330 0.325 0.327 0.320 0.326
... ... ... ... ... ... ... .. ...
0:046
0:330
0.329 0.331 0:328
...
ERROR
.....
-0.001 +O.OOl -0.004 +0.001 + O . 003 -0,002 -0.004
.....
+O.OOl
0.000 -0.004 0.000 0.000 -0.006
.....
-0.013 +0.003 -0.005 +0.002 -0.003 -0.001 -0.008 -0.002
.....
-0.001 +0.002 +0.004 +0.002 $0.001 -0.005
.....
...
+0.005 +0.007 +0.002 +0.001 +0.004
-n
%
0.328 0.323 0.330 0.332 0.330 0.330 0.323
+O.OOl + O . 006 +O. 004 +o. 001 +0.001 -0.003
..... ..... ..... ..... ..... ..... ..... ..... .....
...
...
no4
+O.Oll +0.002 +0.001 +O. 004 -0.002 +0.006
%
’
.....
+0.002 +0.002 +o, 100 +0.004
... ... . . ~ ... ... ... ... ... ...
... ... ... ... ... ... ... ... ... 0.280 0.275 0.2so 0.272 0.280
.....
.....
.....
... ... ... ...
-0.005 0.000 -0.008 0.000
OXYGENBOMB CHLORINE FOUND BY LAMP % 0,040 0.324 0.406 0.347 0.264 0.296 0.386 0.038 0.021
ERROR
.....
-0.001 +0.016 +0.006 +0.002 +0.002 +o.o09 +0.006
$0.001
SULFUR FOUNDSULFUR FOUND BY BOXB BY L A M P
%
%
0.282 0.280
0.280 0.280
...
...
... ...
0:325 0.327
... ... ...
:
0 329 0.329
upon the chemical structure of the chlorohydrocarbon present. I n practically every determination the percentage of chlorine found is slightly higher than the quantity added, although the differences are well within the accepted limits of error of the lamp sulfur determination. In the case of gasolines containing percentages less than 0.10 of chlorine and sulfur, 0.05 N or 0.01 N silver nitrate can be advantageously used. Best results are obtained by concentrating the solution after titration with sulfuric acid to not over 25 cc. The potassium chromate indicator should be a concentrated solution. If the acid titration is carried beyond the end point as shown by the methyl orange indicator, a few drops of sodium carbonate should be added to make the solution neutral. The high-sulfur gasoline did not burn very readily. This is apparently due to the highly aromatic content of this
March 15, 1933
INDUSTRIAL AND ENGINEERING CHEMISTRY
particular material. The flame yielded a “smoky” absorption solution which necessitated filtration in all cases. The samples containing isobutyl and isopropyl chlorides required much attention, smoking much more than any other samples. Regardless of the difficulties, satisfactory results were obtained. The following analyses were made on several gasolines containing various chlorohydrocarbons by the oxygen bomb method (A. S. T. M. designation D-129-27), determining the sulfur by barium sulfate precipitation and the chlorine by titration with silver nitrate. The results were compared to those obtained on the same samples by the lamp method.
87
Excellent check results were obtained between the two procedures. LITERATURE CITED (1) (2) (3) (4)
(5) (6) (7)
(8)
Bowman, J . I n s t . Petroleum Tech., 7, 334 (1921). Kalthoff, Lauer, and Lunde, J . Am. Chem. Soc., 51,3273 (1929). Lemp and Broderson, Ibid., 39, 2069 (1917). Parr and Lemp, Ibid., 30, 764 (1908). Scott, “Organic Analysis,” 4th ed., Vol. 1, pp. 149-150, Van Nostrand, 1918. Smith, W. C., IND.ENG.CHEM.,Anal. Ed., 3, 354 (1931). Votocek, Chem. Listy, 16, 248 (1922). Willard and Thompson, J . Am. Chem. Soc., 52, 1893 (1930).
RECEIVED November 2 5 , 1932.
Determination and Occurrence of Fluorides in Sea Water THOMAS G. THOMPSON AND HOWARD JEAN TAYLOR, University of Washington, Seattle, Wash. The occurrence and determination of fluorides alkaline solution, nearly half the 1850 E’orchhammer (6) fluoride remained in solution. obtained 0.7 mg. of fluorin sea water have received scant attention, and the In the development of an anaine per liter of sea water data that have been obtained show marked varialytical procedure, the methods of collected near C o p e n h a g e n . tion. The authors have adapted the zirconium Casares and Casares (S) and De Carnot in 1895 (a) in a sample of nitrate-sodium alizarin sulfonate indicator for Boer (4) have been modified to water from the Atlantic found the determination of fluorides. The chloride and meet the conditions encountered. 0.82 mg. per liter, while Carles Zirconium nitrate and sodium ( I ) , a few years later, reported sulfate ions of sea water interfered with the alizarin sulfonate react to form a as h i g h as 12 m g . i n w a t e r determination, but the dificulty is eliminated by b r i l l i a n t r e d d i s h violet lake f r o m the Basin of Archachon. preparation of comparison standards containing which is stable in acid solution. Gautier and Clausmann (6) obthe same quantity of these ions as a sample of sea De B o e r h a s s h o w n t h a t a tained results in the waters of water being studied. The speed of the reaction number of metallic salts form a the Atlantic and Mediterranean lake with this particular dye but that varied between 0.240 and between the zirconium alizarin lake and the only two, zirconium and hafnium, 0.334 mg. per liter. fluoride ion is increased by heating, thus maare stable in the presence of hyForchhammer determined the terially reducing the time necessary to reach drochloric acid. Samples of sea fluoride by first precipitating it as equilibrium and making the determination more water, when treated with sodium calcium fluoride. Sulfuric acid rapid. For ocean waters, the fluoride ion is alizarin s u l f o n a t e , s h o w e d a was added to the precipitate and coloration which completely disthe extent to which the liberated proportionate to the chlorinity, the fluorideappeared upon the addition of hydrofluoric acid e t c h e d glass chlorinity constant being 7.0 x 10-6. Surface hydrochloric acid. The stable was used as a measure of the coastal waters and other waters that are subjected reddish violet color produced by amount actually present. Carles to dilution appear to give a slightly higher zirconium nitrate a n d s o d i u m used much the same method but fluoride-chlorinity ratio. alizarin sulfonate in acid soluprecipitated as barium fluoride. tion, however, is destroyed bv Carnot evaDorated large auantities of watkr to whicuh calcium hydroxide had been added. the addition of fluorides, the pale yellow color of the alizarin After washing the precipitate free of soluble salts and treating sulfonate reappearing. Thus conditions may be created where it with acetic acid to rid it of calcium carbonate, silica and various amounts of fluoride will react with the same amount sulfuric acid were added. The liberated silicon tetrafluoride of the lake under identical conditions and cause the formawas conducted through a solution of a potassium salt, and the tion of a color series ranging from a red to a yellow. Applying the method directly to sea water, two difficulties potassium fluosilicate precipitated and weighed. Gautier and Clausmann precipitated the fluorides as barium are encountered-the effect of various salt concentrations fluoride by the addition of barium chloride. Barium sul- upon the indicator and the marked slowness of the reactionfate was precipitated simultaneously, retaining a portion but these have been largely eliminated by modification of of the fluorides. By an elaborate treatment of the precipi- the method. tates in special apparatus, lead fluoride was eventually METHODOF ANALYSIS obtained and converted to colloidal lead sulfide, which was Dissolve 0.87 gram of crystalline PREPARATION OF INDICATOR. measured colorimetrically against known standards, and the zirconium nitrate in 100 ml. of water. Dissolve 0.17 gram of amount of fluorides present deduced from the quantity of lead sodium alizarin sulfonate in 100 ml. of water. Mix the two sulfide. solutions. Dilute 15 ml. of the resulting mixture to 100 ml. to Investigation of these methods shows that a relatively serve as indicator. SODIUM FLUORIDE SOLUTION.Weigh out exactly large portion of the fluorides was not precipitated and was 222STANDARD mg. of pure, dry sodium fluoride and dissolve in 1 liter of found in the filtrate. When a sample of sea water containing water. When 100 ml. of this solution are diluted to 1 liter, 1 ml. 1.25 mg. of fluorine was heated with barium chloride in is equivalent to 0.01 mg. of fluorine.
I
1\’
