INDUSTRIAL AND ENGINEERING CHEMISTRY
390
TABLE IV.
Aclinowledgments
PROPERTIES OF HIGH-VISCOSITY OILS
Refractive Density -Sample----. Index a t at No. Description 20.0’ C. 20.0’ C. 0-19 Sh$l sample 3, 1.588b 1.0225 heavy aromatic” 0-22 Shellsample 3 BL 1.559b 0.9976 38 Shell sample 5, 1 . 6 0 2 0 0.9015 olymerired isoEutylene a Conversion by A. S,T. M. method D446-37T. b Too dark for accurate observation.
Viscosity at: 210’ F. (98.9’ C.) XineSaybolt matic Saybolt Universal‘ stokes Universala .. 3.184 1,481
130’ F. (64.4’ C.)
Kinematic stokes
..
50.06
..
23,170
..
large amounts of the solution in the determination, permitted only two runs to be made on this material. The separation or identification of the data for individual runs (Figure 3) is impossible for this sample as well as for the lower molecular weight samples 0-19 and 0-22 in which three and four runs, made* the precision Of the determination is better than per cent there is no logica1 reason for believing that these samples behaved differently than did the four test oils. Consequently, if it can be assumed that the cryoscopic method used in this investigation gives correct molecular weights with undiluted samples, then the results obtained on the ViSCOUS Oils may be considered as being accurate to * 2 per cent.
VOL. 11, NO. 7
1.661 103.4
773 48,000
Of the seven samples used in this investigation four (0-15, 0-19, 0-22, and 38) were supplied by the Shell Development Company of Emeryville, Calif., and one (0-18) by the Mid-Continent Petroleum Corporation, Tulsa, Okla. The writers are grateful to S. Tijmstra and his eo-workers of the Shell Development Company for their active interest and cooperation in problems relating to the molecular weights of petroleum fractions. Literature Cited
(1) Headington, C. E., “Science of Petroleum”, p. 1295, London, Oxford University Press, 1938. (2) Keith, J. R., and Roess, L. C., IND.E m . CHEY.,29, 460 (1937). (3) Mair, B. J., and Willingham, C. R., Bur. Standards J . Research, 21,535 (1938). (4) RalL H. T.,and Smith, H. M., IND.ENQ.CHEM.,Anal. Ed., 8, 324 (1936). ( 5 ) Ibid., 8, 436 (1936). ~ T J by Bpermission ~ ~ of the ~ Director, ~ ~ Bureau ~ of Mines, U. S. Department of the Interior. (Not subject t o copyright.)
Determining the Amyl Alcohol Content of Distilled Spirits S. T. SCHICICTANZ AND A. D. ETIENNE, U. S. Treasury Department Laboratory, Washington, D. C.
I
N T H E production of ethyl alcohol by fermentation there is produced a group of higher alcohols generically known
as “fusel oils”, which constitute an essential part of the congeners of alcoholic beverages. Although the fusel oil fraction is necessary for odor and taste characteristics, the amounts present are extremely small and range between 70 and 250 grams per 100 liters of distilled spirit. Since the fusel oil fraction is used as a step in the assay analysis of distilled beverages, many tests have been ‘developed for their quantitative determination. The preferred method of Allen-Marquardt, which is the official method and adopted as the standard by the Association of Official Agricultural Chemists, estimates the fusel oil content by extraction with carbon tetrachloride and subsequent oxidation to the respective acids, which are then quantitatively estimated by titration with standard 0.1 N sodium hydroxide. Modifications of this method have been described by Tolman and Hillyer (6) and Mitchell and Smith (6). Herzfeld and Rose (7, 9) describe a method by which the fusel oil is determined by a measure of the increase in the volume of chloroform used as the extractant. Komarowsky (4) determined the fusel oils by means of a color reaction. Many authors ( I , 3 , 5 , IO) have inveqtigated the reactions responsible for the color produced by the combination of the alcohols of higher molecular weight with cyclic aldehydes such as salicylaldehyde, vanillin, veratic aldehyde, and p-dimethylaminobenzaldehyde. Penniman, Smith, and Lawshe (8) describe a method of analysis which appears to yield a true value for the fusel oil content of a distilled
spirit. However, their high values may be in error because during the treatment of the beverage with sulfuric acid and alkaline silver nitrate there is produced some acetic acid which reacts with the cyclic aldehydes and produces additional color ( 2 ) . In the present method, the fusel oil, separated from the distilled spirit by distillation and subsequent extraction with carbon tetrachloride, is determined by esterification with acetyl chloride (1%). After the reaction is completed, the excess acetyl chloride is decomposed and titrated. The difference in titer between the sample and a blank gives the moles of acetic acid removed by esterification with the higher alcohols. Reagents Eastman’s reagent grade acetyl chloride is used in preparing a 0.23 M (molal) solution in dry toluene. The pyridine solution is made approximately 0.50 M in toluene. Both solutions may be kept safely in regular well-ground glass-stoppered bottles. Apparatus The distillation unit recommended by the official AllenMarquardt method is used to separate the fusel oil fraction and other volatile constituents from the solids of the whisky. The reaction flask, shown in Figure 1, is made from a 125ml. Erlenmeyer flask to which is attached a standard-taper ground joint No. 15. The neck of the flask is elongated as shown in order to assure no loss of reagents during pipetting. I n Figure 2 is shown the dehydration and dealcoholizing still used to remove the ethyl alcohol and mater from the
JULY 15, 1939
ANALYTICAL EDITION
composite carbon tetrachloride extracts. The still is packed with small glass helixes 0.64 cm. (0.125 inch) in diameter.
Procedure The sample of beverage to be analyzed (50 ml.) is placed in a 500-ml. Erlenmeyer flask equipped with a ground joint. Thirty milliliters of 0.1 N sodium hydroxide and a few pieces of silicon carbide (10-mesh) are added, and the flask is attached to the AllenMarquardt distillation unit. When 45 ml. of distillate have been collected in a 125-ml. separatory funnel, the distillation is stopped and 25 ml. of distilled water are added to the residue. Distillation is then continued until the total volume of distillate is approximately 65 ml. To the distillate are now added 10 ml. of distilled water and 10 grams of sodium chloride and the contents are well shaken to dissolve most of the salt before beginning the extraction with carbon tetrachloride. The extraction consists of four consecutive treatments with 40-, 30-, 20-, and 10-m1. portions of carbon tetrachloride, shaking a t least 15 seconds upon each addition of carbon tetrachloride. The carbon tetrachloride ) extract is collected in the reaction FIGURE 1 flask (Figure 1) to which have been added a Tew pieces of silicon carbide to ensure even boiling. The reaction flask is attached to the still (Figure 2) and 50 ml. of distillate are collected bv allowing the still to reflux for 5 minutes before removing the first fractkn and then removing nine more consecutive fractions at 5-minute intervals. The reaction flask is allowed to cool 1 minute, removed while still warm, loosely stop ered, and cooled for from 3 to 5 minutes in an ice bath. To &e flask are now added 5 ml. of pyridine solution and 10 ml. of acetyl chloride solution from precision pipets, being sure during the pipetting procedure that the respective reagents are introduced well down in the flask. Immediately following the addition of the acetyl chloride solution the flask should be tightly stoppered. It is advisable to put a very small amount of lubricant on the stopper (just enough to make a seal but not enough to allow the stopper to blow out of the flask during the following heating period). The stoppered flask is then shaken and placed in a water bath ( l a ) kept at 60" C. The flask is allowed to remain in the bath for 30 minutes with shaking every 5 minutes. It is then placed in an ice bath for 5 minutes, after which 25 ml. of water are added, washing down the neck of the flask during the addition. After the flask has been shaken to decompose all pyridine salts and to extract the acids into the aqueous layer, an excess (1 to 3 ml.) of 0.100 N sodium hydroxide is added from a buret, the flask is shaken vigorously, 4 or 5 drops of phenolphthalein are added, and the solution is back-titrated to a light pink with 0.100 N sulfuric acid. A blank should be run with each set of experiments and the alcoholic hydroxyl groups in the sample estimated as the difference in alkali used between the sample and that of the blank. One milliliter of 0.1 N sodium hydroxide is equivalent to 0.0001 mole of fusel oil or 0.0088 gram of fusel oil or 17.6 grams of fusel oil per 100,000, calculated as amyl alcohol. The accuracy of the method was tested by using a carbon tetrachloride solution containing a known amount of sec-butylcarbinol. The latter had a refractive index a t 25' C. of 1.4084 and boiled between 129.35' and 129.55' C. In all experiments the results indicated a recovery of approximately 96 per cent, which may be assumed to be quantitative, since the alcohol used had a boiling range of 0.2" C. and undoubtedly contained a small percentage of inert substance.
(
Because of the small concentrations of amyl alcohol used, it was found necessary to heat the reaction mixture at least 30 minutes during esterification. In Table I are given the results obtained by heating for 20 and 30 minutes, respectively.
391
Heating for longer than 30 minutes is apparently not necessary. I n one experiment see-butylcarbinol was extracted from a n ethyl alcohol solution with carbon tetrachloride and subsequently freed from ethyl alcohol and water by distillation prior to the esterification process. One set of samples was heated for 30 minutes and another set for 40 minutes, yet the same number of moles of alcohol were recovered. TABLE I. EFFECTOF HEATING Time of Heating Mlin.
Alcohol Present Mole
Alcohol Found 1MoZe
20 30
0.000474 0.000474
0 000396 0.0004ti6
According to Smith and Bryant (19) the presence of aldehydes or esters does not interfere with the determination. In Table I1 are given the results obtained when equal molal quantities of acetaldehyde and ethyl acetate dissolved in carbon tetrachloride were added to the carbon tetrachloride solution of see-butylcarbinol prior to the determination. TABLE 11. EFFECTOF ALDEHYDES AND ESTERS Sec-Butylcarbinol Mole
Ethyl Acetate Mole
0.00047 0,00047 0,00047
0 0.00065 0
Acetaldehyde Mole 0 0
Approx. 0.001
Alcohol Found
Mole 0.000410 0,00041?, 0,000420
Further confirmation, presumably, of the negative effect of esters was obtained by determining the fusel oil content of a whisky by distilling immediately upon the addition of alkali, and by refluxing the whisky for 0.5 hour with alkali prior to distillation. The results are given in Table I11 and indicate either that complete saponification had occurred during the distillation process, or that esters do not interfere with the test. Although the results obtained on solutions of see-butylcarbinol in carbon tetrachloride were practically quantitative Capacity (96 per cent), it became J5ml. evident that the results obtained on sec-butylcarbinol in 100-proof ethyl alcohol showed a recovery of only approximately 83 per cent. By experiment it was shown that the loss occurred in the extraction process, and the magnitude of the loss was proportional to the volume of solution ( e t h y 1 a 1coho 1-water) containing the sec-butylcarbinol. I n one set of experiments, 50ml. of 100-proof alcohol containing secbutylcarbinol were diFIGURE2. DISTILLATION luted with 50 ml. of satuUNIT
INDUSTRIAL AND ENGINEERING CHEMISTRY
392
rated salt and then extracted, while in another set 50 ml. of 100-proof ethyl alcohol containing see-butylcarbinol were diluted with 110 ml. of saturated salt solution. The moles of alcohol recovered were 0.000459 and 0.000411, respectively, which indicates a loss of approximately 10 per cent of seebutyl alcohol in the solution having the greater volume. TABLE111. EFFECT OF REFLUXING Treatment Prior t o Distillation Distilled immediately Reflux 0.5 hour prior t o distillation
Alcohols Esterified Mole 0.00102 0.00102
Accordingly, the method for the initial distillation of the whisky was modified to yield a small volume of distillate which would be sure to contain all of the fusel oil fraction. I n Table IV are given the results obtained, which indicate that all of the fusel oil fraction was recovered by the modified method of distillation and that the loss in fusel oil presumably occurs in the extraction process.
Comparison of A. 0. A. C. and Acetyl Chloride Methods The acetyl chloride-pyridine method of analysis offers considerable advantage over the official A. 0. A. C. method. The time required for a complete analysis by the acetyl chloride method is approximately 3 hours by virtue of the elimination of the lengthy oxidation procedure. The method is not affected by aldehydes, which if present in the whisky must be removed prior to the analysis according to the official method. Since esters do not affect the results, saponification prior to the initial distillation is not necessary. By obtaining only 65 ml. of distillate instead of 110 ml., the time required for the initial distillation is almost halved. Further, it is not necessary to saturate the distillate to a definite salt concentration, since an excess of salt does not affect the results of the new method. Errors in the regular extraction procedure are reduced, since after the initial extraction of the alcohols with carbon tetrachloride, the present procedure removes traces of water and ethyl alcohol by simple distillation rather than by subsequent extraction with saturated sodium chloride solution followed by extraction with saturated sodium sulfate solution.
TABLE IV. EFFECT OF MODIFIED METHOD (Mixture of see-butylcarbinol in 100-proof eth 1 alcohol) Alooho? Alcohol Treatment of Sample Present Recovered Mole Mole Modified d$tillation and extraction 0.00046 0.000377 No distillation, only extractlon 0.00046 0.000380
During the distillation procedure used for the dehydration and dealcoholization of the carbon tetrachloride extract, the ternary azeotrope ethyl alcohol, water, and carbon tetrachloride are removed first. Dry ethyl alcohol remaining after the water has been removed then forms a binary azeotrope with carbon tetrachloride which has a boiling point approximately 11.5" C. below that of carbon tetrachloride itself, and is readily removed. It is fortunate that carbon tetrachloride does not form any azeotropes with alcohols boiling above n-butyl alcohol by virtue of the wide difference in boiling points between carbon tetrachloride and the higher alcohols The azeotropic power as exhibited by carbon tetrachloride with alcohols is conducive to a simple distillation procedure for the removal of extraneous amounts of ethyl alcohol and water. The method allows for a complete removal of the lower alcohols, since distillation can proceed long after the ethyl alcohol has been removed, by distilling only carbon tetrachloride, without fear of the loss of any of the higher alcohols.
VOL. 11, NO. 7
The presence of isopropyl, n-propyl, tert-butyl, and isobutyl alcohols and their removal during the distillation procedure would indicate a decrease in value for fusel oils. It may be assumed that a similar decrease in fusel oil value is obtained by the official method, since the percentage amounts of alcohols lower than the amyls present in fusel oil are small, and, too, that since the solubility of the low boiling alcohols is more closely related to the solubility of ethyl alcohol than the amyls, the extraction of the carbon tetrachloride extract with saturated sodium chloride and sodium sulfate solution would remove a considerable portion. After removal of the water and alcohol from the carbon tetrachloride extract, the fusel oils present require only 30 minutes for complete esterification; whereas an oxidation procedure requires a t least 8 hours, plus a subsequent distillation. The subsequent titration of the excess acetyl chloride is analogous to that of the official method, using 0.1 N sodium hydroxide as titer and phenolphthalein as indicator. However, since the results depend on the determination by difference between the amount of acetyl chloride added and the amount remaining after esterification, it is necessary to know accurately the amount of acetyl chloride added. TABLE V. COMPARISON OF METHODS Treatment Residue Distillate Not distilled
Allen-Marquardt 0.000355 0.000049 0.000395
Aoetyl Chloride 0.00035
..... .....
In Table V is given a comparison of the results obtained by the two methods using a standard sample of sec-butylcarbinol in solution in 50 per cent ethyl alcohol. The samples of sec-butylcarbinol in 50 per cent ethyl alcohol were subjected to the following procedure prior to the oxidation and esterification reactions. Fifty milliliters of see-butylcarbinol solution were diluted with saturated salt solution and sodium chloride to a density of 1.1. This was then extracted with 40-, 30-, 20-, and 10-ml. portions of carbon tetrachloride and the extract washed three and two times with saturated sodium chloride and sodium sulfate solutions, respectively. The solutions were then subjected to distillation in the dehydration stills and 50 ml. distilled off as distillate. Because of the large excess of water present, the acetyl chloride method could not be applied successfully to determine the amounts of alcohols contained in the distillates. However, the usual method of procedure as outlined in the Allen-Marquardt method allows a considerable amount of ethyl alcohol to remain in the carbon tetrachloride extract, which in the usual procedure attributes considerably to the final evaluation of fusel oil content. TABLEVI. COMPARISON OF METHODS Treatment Residue Distillate Not distilled
Allen-Marqusrdt 0.000997 0.000200 0.001 180
Aoetyl Chloride 0.00096 0,00045 0.00145
I n another experiment using a standard sample of whisky, it was again evident that results obtained by the Allen-Marquardt method are too high, owing to the existence of some ethyl alcohol in the carbon tetrachloride extract. The results of the experiments are given in Table VI. The samples were subjected to the same treatment prior to distillation as the sec-butylcarbinol solution, except that the esters in the whisky were destroyed by the usual method subsequent to the distillation to remove extraneous solid or nondistillable material from the fusel oil fraction. It is again evident that considerable amounts of ethyl alcohol are present in the carbon tetrachloride extract and con-
JULY 15, 1939
ANALYTICAL EDITION
tribute to the value of fusel oil as normally determined. However, the acetyl chloride method indicates the presence of considerably more alcoholic hydroxyl groups than the Allen-Marquardt method. The major portion of the difference lies in the distillate, and indicates that the oxidation procedure is not capable of oxidizing quantitatively ethyl alcohol to the corresponding acid. This fact was corroborated by another set of experiments in which carbon tetrachloride containing a small amount of ethyl alcohol was subjected to both procedures. By the Allen-Marquardt method 0.00074 mole of alcohol was recovered; by the acetyl chloride method, 0.000975 mole. This is in agreement with the conclusions of Schidrowitz and Kaye ( 2 1 ) , who indicated that ethyl a1coho1 was not oxidized quantitatively during the oxidation procedure. In the Allen-Marquardt method a blank must be run to determine the acidity produced by the carbon tetrachloride in the oxidation procedure. TABLEVII. CCId Used Ml. 25 50 100
GENERATION OF ACIDS Acid Found Mole 0,000020 0.000025 0.000020
Several experiments were made to determine the true cause of the generation of acids during the oxidation procedure. The results, given in Table VII, indicate that the acids are not generated by virtue of impurities in the carbon tetrachloride but by the partial decomposition of the carbon tetrachloride itself. It is evident that the evaluation of fusel oil in distilled spirits
393
depends upon the method used for the determination. Each method produces accurate values which are relative, but not in agreement when compared with values obtained by different procedures. Each procedure, used previously, is not specific for alcoholic hydroxyl groups alone, but is affected by the presence of other reactive groupings such as aldehydes, unsaturates, and esters. The acetyl chloride esterification procedure is normally not affected by the presence of these groupings and tends to give values which are specific for hydroxyl groups. However, according to the method as outlined for the acetyl procedure, any alcohol below n-butyl will be excluded from the fusel oil value. I n view of these considerations, the results obtained by the acetyl chloride method are designated as an “amyl alcohol” value and not as a “fusel oil” value.
Literature Cited (1) Bleyer, B., Diemair, W., and Frank, E., 2. Untersuch. Lebensm., 66, 389 (1933). (2) Budagyan, F., and Ivanova, N., Ibid., 63,200 (1932). (3) Fellenberg, Th. von, Chem.-Ztg., 34, 791 (1910). (4) Komarowsky, Ibid., 27, 807, 1086 (1903). (5) Korenmann, J., 2. anal. Chem., 88, 249 (1932). (6) Leach, “Food Inspection and Analysis”, p. 780, New York, John Wiley & Sons, 1930. (7) Lunge, G., “Technical Methods of Chemical Analysis”, p. 726, New York, D. Van Nostrand Co., 1914. (8) Penniman, W. B. D., Smith, D. C., and Lawshe, E. I., IND. ENG.CHEM.,Anal. Ed., 9, 91 (1937). (9) Rose, Stutzer, and Windisch, Arb. kaiserl. Gesundh., 5, 391 (1889). (10) Ruppin, E., 2. Untersuch. Lebensm., 66,389 (1933). (11) Sohidrowitz and Kaye, Analyst, 30, 190 (1905). (12) Smith, D. M., and Bryant, W. M. D., J. Am. Chem. Soc., 57, 61 (1935).
Kniaseff Fat Test HORACE H. SELBY
AND
THELMA A. SELBY, Hage’s, Ltd., San Diego, Calif.
F
OR twelve years the writers have made comparative analyses of ice creams and ice milks, taking the methods
of Mojonnier and the Association of Official Agricultural Chemists as standard, and attempting to correlate the results of some twenty-five modifications of the Babcock method with the standard results. With only one method has it been possible to obtain even approximate results consistently in a series of comparisons when a suitably wide range (4 to 20 per cent) of fat content has been employed. The exceptional method is that of Kniaseff (W), which, in the authors’ hands, has yielded results of a high order of accuracy when suitable corrections have been applied. The method is lengthy, however, and the advantage of speed which Babcock-type methods inherently possess over the solvent-extraction methods is lost, if but one or two estimations are to be made. The purpose of this note is to outline minor changes in the Kniaseff procedure which appear to increase the accuracy and the speed attainable.
Reagents and Procedure REAGENT I. Distilled water, 1000 ml.; sodium hydroxide, A. C. S., 132 rams; ammonium sulfate, A. C. S., 42.8 grams. REAGENT Ethyl alcohol, U. S. P., 391 ml.; n-butyl alcohol, b. p. 116-118’ C., 24 ml.; ammonium hydroxide,
8.
A. C. S., 24 ml.; ethyl ether, A. C. S., 94 ml.; petroleum ether, b. p. 26-31’ C., 94 ml. PROCEDURE. 1. Weigh 9 * 0.02-gram duplicate samples into 9-inch, 9-gram, 50 per cent Babcock cream test bottles which have been proved accurate by mercury calibration. The writers discarded bottles with errors greater than 0.1 per cent in the ranges 50 to 40 per cent, 50 to 30 per cent, and 50 to 20 per cent. 2. Add 8 * 0.1 ml. of reagent I. Shake 5 seconds with rotary movement. 3. Add 5 * 0.1 ml. of reagent 11. Shake 10 seconds. 4. Digest 5 minutes at 84 * 1’ C., shaking 5 seconds after 1.5, 3.5, and 5 minutes. If foam rises above 40 per cent mark, remove bottle for an instant, then reimmerse. 5. Centrifuge 30 * 5 seconds at relative centrifugal force of 165 X gravity a t base of bottle at 65 * 5‘ C. 6. Add tap water at 70 * 5” C. to base of neck. Do not agitate. 7. Centrifuge 30 * 5 seconds as before. 8. Add water t o 50 per cent mark. 9. Centrifuge 60 * 5 seconds. 10. Place in water bath at 60 * 2’ C., so adjusted that temperature falls to 57” C. in 10 t o 20 minutes. 11. When temperature reaches 57 * 0.5” C., add oil and read. 12. Multiply reading by appropriate factor, K , obtained from Figure 1 .
I. CHANGES IN KNIASEFF PROCEDURE. Reagent I1 under-
goes some change in composition due possibly to amine forma-
