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
Jan., 1918
REAGENTS FOR USE IN GAS ANALYSIS VII-THE DETERMINATION OF BENZENE VAPOR By R. P. ANDERSON Received August 16, 1917
I n connection with t h e development of a new method for t h e determination o€ benzene vapor in gas, a brief history of t h e determination of this substance has been prepared, and is here presented. Following this historical summary, there is a brief statement of t h e principle of this new method, upon which considerable preliminary work has been done. The various methods t h a t have been employed are taken up in chronological order. FCXIISG S I T R I C ACID V E T H O D
Berthelotl appears t o have been t h e first t o suggest a procedure for t h e determination of benzene vapor in illuminating gases. A sample of gas whose benzene content was desired was placed in contact with fuming nitric acid and t h e approximate amount of benzene determined either by weighing t h e dinitrobenzene formed or b y determining t h e decrease in volume of t h e sample. Olefines were removed b y bromine water previous t o t h e treatment with fuming nitric acid. Treadwell and Stokes2 found t h a t t h e volumetric method gave unreliable results because treatment with bromine water for t h e removal of olefines results in the absorption of some of t h e benzene, and because fuming nitric acid, t h e reagent for benzene, also oxidizes carbon monoxide. Drehschmidt3 found t h e method unsatisfactory for t h e same reasons, and it does not appear t o have been used t o a n y great extent. D I N I T R 0 B E X Z E NE LIE T H 0 D
T h e gravimetric method suggested by Berthelot was developed by Harbeck and Lunge4 into one with which accurate results can be obtained. T h e gas t o be eyarnined is passed through a mixture of equal parts of fuming nitric acid and concentrated sulfuric acid, thereby quantitatively converting t h e benzene vapor into dinitrobenzene. T h e separation of t h e greater p a r t of t h e dinitrobenzene from t h e acid is effected b y diluting with water and neutralizing with sodium hydroxide. T h e crystals of dinitrobenzene which separate from t h e liquid on standing are separated b y filtration, dried, and weighed. T h e dinitrobenzene remaining in solution is recovered by extraction with ether. T h e procedure recommended b y Pfeiffer’ differs from t h a t just described in t h a t t h e nitration is carried out on a sample of gas enclosed in a special container and in t h a t t h e dinitrobenzene t h a t is formed is not weighed, b u t is titrated with stannous chloride according t o t h e method of Limpricht.6 C 0 21B U S T I 0 N MET H 0 D
B ~ n s e n ,b~y making combustions on samples of illuminating gas before and after the absorption of 1 Compt. rend., 82 (1876), 871, 927; 83 (1876). 1255; Ann. chim. phys.. 151 10 (1877), 171; 12 (1877), 289; Bull. SOL. cham., 50 (1888), 660. 2 Ber., 2: (1888). 3131. Chem.-techn. Analyse,” 2nd Ed., Vol. I, pp. 108, 179. 8 Post. 4 Z . anorg. C h e m , 16 (1898). 41. 5 J. Gasbel.. 42 (1899), 698; Chem.-Ztg., 28 (1904). 884. 6 Ber.. 11 11878). 35. 7 “Gasometrische Methoden,” 1877, 2nd Ed., p. 142. ~I
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benzene vapor and olefines b y fuming sulfuric acid, obtained d a t a from which he computed t h e amounts of benzene, ethylene, and propylene. The accuracy of this method depends upon t h e amount of other hydrocarbons, absorbable b y fuming sulfuric acid, which may be present in t h e gas. ALCOHOL METHOD
Bunsen1 also determined t h e amount of benzene vapor and other hydrocarbon vapors present in illuminating gases b y absorption in absolute alcohol. T h e hydrocarbons t h u s removed from t h e gas, consisting chiefly of benzene, are separated from the alcohol by pouring it into a large volume of a concentrated solution of sodium chloride, whereupon t h e hydrocarbons are obtained as a n oily liquid upon t h e surface of the salt solution. Their amount is determined by weighing. By t h e method of Hempel and Dennis,2 alcohol may be employed for t h e gas-volumetric determination of benzene vapor b y employing I cc. of absolute alcohol in a pipette over mercury, and measuring the decrease in volume t h a t results from contact of gas with t h e alcohol. Later Dennis and O’Neil13 showed t h a t , while concordant results may be obtained by t h e alcohol method, absorption of benzene b y this reagent is b y no means complete. P H O T 0M E T R I C
XI E T H OD
Knublauch4 has devised a method for t h e determination of benzene and ethylene in illuminating gases based upon the determination of t h e illuminating power of t h e gas and the total amount of benzene and ethylene present. From these d a t a and a knowledge of the illuminating powers of benzene and ethylene in t h e pure state, t h e amounts of each can be determined. G r a d 6 has utilized t h e photometric method b y comparing t h e illuminating values of t h e gas before and after t h e removal of benzene. I n t h e method employed b y Reineke,6 t h e amount of benzene is determined from t h e candle power of t h e flame, possible variations in t h e luminosity due t o other constituents of t h e gas being disregarded. CONDENSATION METHOD
Deville’ has developed a method €or determining t h e C. benzene vapor in gas mixtures b y cooling t o - 2 2 ’ and weighing t h e solid benzene which separates. Correction must be made for t h e vapor pressure of benzene a t the temperature employed. Application of the principle of this method has been made b y Neubeck.8 According t o t h e procedure followed b y Burrell and R o b e r t ~ o n ,t ~ h e benzene vapor is condensed from a sample of gas by using a mixture of solid carbon dioxide and ether or acetone as a refrigerant. T h e gas which remains is pumped out and then t h e benzene is allowed Methoden,” 1877, 2nd Ed., p. 144. Ber., 24 (1891). 1162; J . Gasbel., 34 (1891), 414. 8 J . A m . Chem. Soc., 25 (1903). 503. 4 J . Gasbel., 22 (1879). 652; 23 (1880). 253, 274. 5 U. S. Patent No. 1,163,654, December. 1915. 6 German Patent No. 285.920, June, 1914. 7 J . Gasbel., 32 (1889), 652. See also anonymous article in Gas World, 8 Ibid., 58 (1915), 616. 64 (1916). . , 224. 9 THIS JOURNAL, 7 (1915), 669 1 “Gasometrische
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t o vaporize, the pressure exerted by t h e vapor being
determined from a manometer attached t o t h e apparatus. Knowing t h e atmospheric pressure, the per cent b y volume of benzene vapor is computed. A modification of the apparatus employed by Burrell and Robertson has been suggested by Whitonl as being more desirable for use in determining the efficiency of t h e benzol scrubbers used on coke-oven gas. F U M I N G S U L F U R I C ACID M E T H O D
The determination of the combined benzene and ethylene content of an illuminating gas by fuming sulfuric acid may be utilized for the indirect determination of benzene when the amount of ethylene is determined by some other method. Haber and Oechelhauser2 have employed this procedure, determining t h e ethylene content of the gas mixture by treatment with standardized bromine water, and subsequent determination of the excess of bromine. Since benzene is also absorbed by bromine water, t h e combined benzene and ethylene content can be determined approximately by bromine water, as well as by fuming sulfuric acid. Haber and Lunge3 have described a method for determining ethylene in t h e presence of benzene by causing the ethylene t o combine with hydrogen in t h e presence of platinum black. The amount of benzene is then arrived a t indirectly by taking the difference between the combined benzene and olefine content, as determined by fuming sulfuric acid, and the ethylene content. P A R A F F I N OIL METHOD
Miiller4 has proposed t h a t benzene vapor in illuminating gas be determined by passing the gas through cooled paraffin oil. The greater part of the benzene vapor can be absorbed by this method. Nowicki6 had described a special absorbing device for carrying out this determination. The method has been elaborated by Krieger.E Neubeck’ has modified the procedure by distilling off t h e benzene taken up by t h e oil, b u t does not recommend the method on account of t h e difficulty in maintaining air-tight joints during t h e distillation. Copps has described the procedure adopted by him in obtaining more efficient absorption of the benzene vapor. SPECIFIC GRAVITY METHOD
I n Lunge’s “Chemisch-technische Untersuchungsmethoden,” Vol. z ( I ~ o o ) ,p. 586, there is described a method for determining t h e benzene content of a n illuminating gas from the specific gravity of the gas and t h e amount of olefines in it. This method is open t o the objection t h a t possible variations in the amounts of t h e other constituents of the gas are not considered.
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THISJOURNAL,8 (1916). 733.
* Ber.. 29 (1896). 2700; J . Gasbel.. 39 (1896), * 2. anorg. Chem., 16 (1898), 26. J . Gasbel.. 41 (1898), 433. Ibid.. 48 (1905). 292. 6 Ibid., 68 (1915). 61. Ibid., 68 (1915), 815. 8 Gas World, 66 (1917), 222. J . Am. Chem. SOC..26 (1903), 503. 4
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SULFURIC ACID METHOD
MortonZ has suggested t h e use of concentrated sulfuric acid for the absorption of benzene vapor in the presence of ethylene. Dennis and McCarthya found t h a t this reagent does not give satisfactory results both on account of the fact t h a t some ethylene is absorbed by it, and also because t h e absorption of benzene is not complete. SATURATION METHOD
The SociBtB Roubaisienne d’ Eclairage par le Gaz and R R . L. H. Forrieres4 have developed a method for benzene based upon t h e determination of t h e amount of benzene t h a t is required t o saturate a known volume of gas. After computing t h e amount t h a t would be required, under the conditions of the experiment, for gas containing no benzene vapor, the benzene content of the gas is gotten by difference. T H E NEW METHOD
During t h e summer of 1915,in attempting t o develop a method for determining benzene vapor in gas simply, quickly, and accurately, the author did considerable preliminary work upon a method which appears more nearly to satisfy these requirements t h a n any of t h e methods t h a t have been mentioned. I n the proposed method, a measured quantity of gas containing a n unknown amount of benzene vapor is placed in contact with benzene in a special apparatus and the increase in volume read. By determining what the increase in volume would have been, had the gas contained no benzene vapor, t h e amount of benzene vapor actually present is easily computed. T h a t this idea is not entirely new was learned when a search of the literature was made and reference t o t h e German Patent described under t h e previous heading was found. The procedure t h a t has been employed is, however, much simpler and quicker t h a n t h a t described in t h e patent. Owing t o the failure of attempts t o obtain, under present conditions, apparatus considered essential for t h e proper standardization of t h e method, its further development has been temporarily postponed. CORNELLUNIVERSITY ITHACA.NEWYORK
RESEARCH ON THE DETECTION OF ADDED WATER IN MILK By HALSEY DURANDAND RESTON STEVENSON Received September 13, 1917
A t the annual meeting of t h e American Chemical Society, held in New York City, September 27, 1916, one of t h e authors read a paper on “The Detection of Added Water in Milk,”S in which the importance of devising a rapid and accurate method was brought
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as a reagent a n ammoniacal solution of nickel nitrate. Later Dennis and McCarthy’ suggested t h e use of an ammoniacal solution of nickel cyanide instead of nickel nitrate, having found t h a t more uniformly reliable results could be obtained with the former reagent.
AMMONIACAL N I C K E L C Y A N I D E M E T H O D
Dennis and O’NeillQ developed a gas-volumetric method for the determination of benzene, employing
Vol.
J . Am. Cken. Soc., 30 (1908). 233. Ibid., 88 (1906). 1732.
Ibid.. 30 (1908). 233. German Patent No. 267,491. May. 1913. 8 THIS JOURNAL,9 (1917), 44.
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