ILVDU S T R I A L A N D ESGINEERI,VG C H E X I S T R Y
July, 1924
fluoride, gives results corresponding with those obtained with calcium fluoride or fluorspar. This suggests that calcium may be responsible for the low fluorine results by Procedure B. The ratio of calcium to fluorine obtained by this procedure
707
would correspond to the ratio in a complex compound having the formula 8 CaFZ.CaSiF6, 1: 1.18. I n the absence of calcium, and omitting fusion, the compound formed by addition of the standard calcium salt appears to be CaF2.
Influence of Several Solvents on t h e H a n u s Iodine Values of Cottonseed and Coconut Oils' By Herman J. Bankston, Jr., and Frank C. Vilbrandt EMORY UNIVERSITY, ATLANTA, GA.,A N D UNIVERSITY OF NORTHCAROLINA, CHAPELHILL, N. C. EXPERIMEKTA L LTHOUGH the exThis article shows the influence of such solvents as chloroform, The procedure' was that tent to which an orcarbon tetrachloride, ether, ethyl alcohol, and benzene on the Hanus given as an official iodine ganic substance will iodine values of cottonseed oil with a high iodine value, and coconut method by the Association absorb bromine is claimed to oil, with a low iodine oalue. Chloroform and carbon tetrachloride of Official A g r i c u l t u r a l be indicative of the degree gioe higher and more consistent results than ether, alcohol, or benzene, Chemists,* except that the of unsaturation of the fats and their use is not attended with variations due to changes in the quantity of solvents was and oils of which it is comquantity of the solvents used. Chloroform seems to be the superior varied from 0 to 25 cc. I n posed, the iodine method solvent under the conditions studied. order t o eliminate as many is generally used in the factors as possible, 0.5-gram quantitative determination of this degree of unsaturation, the value thus obtained be- samples were used, first dissolved in the solvent, then treated ing used as one of the important tests in the evaluation of with 50 cc. of the Hanus iodine solution in the glass-stoppered bottles and allowed to react with frequent shaking a t 25" C. such organic bodies. It is wtdl known that the methods for the determination of for exactly 30 minutes. The excess iodine was then backthe unsaturation value of an oil or fat by the iodine methods titrated with 0.1 N sodium thiosulfate solution. The iodine are empirical and lend themselves to considerable variance in solution was made approximately 0.1 ATstrength a t first, but the values obtained on the same sample, owing to differences it lost strength slowly and had t o be standardized each in time, concentration, nature of the oil, etc. Even with time it was used: The results are recorded in Table I. these factors carefully controlled, some laboratories suggest Iodine determinations were run on each of the solvents used the interchanging of the solvent used on the oil-i. e., the use and only those specimens were selected that showed no of chloroform, carbon tetrachloride, carbon disulfide, ether, or reaction with this reagent. 8 J . Assoc. O f i c i a l Agr. Chem , 2 , 305 (1916-17). benzene, as the carrier of the oil in order to assist in the speed of the reaction of the iodine on the oil. This practice is TABLE I-IODINE VALUGS OF COTTONSEED AND COCONUT OILSWITH VARIOUS SOLVENTS questionable, as the results of this investigation show. Maximum Chloroforp is uniformly used as the solvent of the oil in Volume of Variation in Solvent Individual the methods proposed by H a n q 2 Hubl,3 and Wallere4 I n Solvent c c. Runs addition, Hub1 used alcohol, not as the solvent for the oil, None None 1,38 but for the iodine; the influence of this alcohol was not 5 2.52 CCla 10 1.35 studied. The oil distributed itself between the chloro- CCla 15 0.30 form and the alcohol. I n the modifications of the iodine CCl4 25 0.47 5 0.10 methods as proposed by Ephraim,6 W i j ~ and , ~ Winkler,7the CHCla CHCli 10 0.07 15 0.77 solvent for the oil was carbon tetrachloride. Wijs used car- CHCli CHCla 25 0.38 bon tetrachloride because he claimed the presence of some CzHiOH 5 2.20 CzH4OH 10 1.60 alcohol in chloroform made this reagent nndesirable. C~HIOH 15 3.30 CzHhOH 25 2 .30 Owing to the instability of carbon disulfide it cannot be CzHdz0 5 0.54 depended upon; hence it was deemed that it would find no CzHsIzO 10 0.11 2 0 15 1.70 general use as a solvent and was not studied in this investi- (CzHs (CzHJzO 25 1.50 CeHa 5 6.00 gation. CeHa 10 0.80 The Hanus method lends itself readily to the study of the CnHe 15 1.70 25 2.80 influence of various solvents, and was therefore used as the C6H6 8.5 None 10.0 9.6 basic method in this investigation. The oils used were cotton- None 10.9 9.8 10.2 9.8 2.40 seed oil with a fairly high iodine value, and coconut oil with a CClr 5 9.6 9.2 9.4 9.4 0.40 9 . 2 CClr 10 8 . 6 9 . 7 9 . 2 1.10 low value. Although benzene and ether are not proposed in CClr 11.6 15 11.1 10.5 11.1 1.10 10.7 25 the standard methods, they were included to determine their CClr 10.3 10.2 10.4 0.05 9.9 CHCli 5 9.0 8.9 2.10 7.8 limits of application. CHCls 10 9 4 9.7 9.7 10.0 0.60
A
1
Received January 26, 1924
Z . Nohv -Genussm , 1, 913 (19011, J Assoc O f i c r a l A g r Chem , 2,305 (1916-17) * Dinslers polytcch J , 263, 281 (1884). * Chem Z f g , 19, 1716, 1831 (1895) Z anqew Chem , 8 , 254 (1895). 8 B e y . , 31, 750 (1898). 7 C h t m Ztg , 39, 744 (1915).
CHCla CHCla CzHsOH CzHsOH CzHsOH CsHsOH (CzHs)zO (CzHs)zO (CzHs)zO C6Ha CnHs C6H6
15 25 5 10 15 25 5
10 25
5 10 15
9 7 11.6 2.2 1 23 2.45 2.54 7.3 10.7 4.1 6.0 7.67 5.3
9.2 10.9 3.4 2.9 3.27 3.82 6.9 9.08 3.8 7.0 6 93 4.5
9.9 1.0
7.1 9.9 3.5 2.0 8.50
9.5 10.8 2.2 2.1 2.86 3.18 7.1 9.89 3.8 5.0 7.67 4.9
0.59
1.70 2.40 1,67 0.82 1.28 0.4 1.62 0.6 5.0 1.57 0.8
708
INDUSTRIAL AND EN 'GINEERING CHEMISTRY
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DISCUSSION OF RESULTS The iodine values of the oils without the use of solvents to hasten the reaction were 93.3 for the cottonseed oil and 9.8 for the coconut oil. The values assigned to these oils, according to Olsen,yare 104 to 115 for the cottonseed and 8 to 10 for the coconut oil. , CARBON TETRACHLORIDE-There are no great irregularities in the iodine values when this solvent is used. The values vary from a minimum of 98.56 with 10 cc. of the solvent to a maximum of 104.92 when 15 cc. were used. The range in the low iodine value coconut oil was from 8.6 to 11.6. The values were more consistent when large quantities of the solvent were used. The variations in the coconut values may not be due to the influence of the solvent, for with an oil of such a low iodine value the unavoidable errors in manipulation and in the method are large. With both the high and low iodine number oils the results with the use of carbon tetrachloride were close enough to consider them constant when 15 cc. or more of the solvent were used with 0.5 gram of the oil. CHLOROFOR&f-The values obtained when chloroform was the solvent were fairly constant, varying from 104.6 to 106.52 for the cottonseed oil and from 7.8 to 11.6 for the coconut oil, a maximum variation of 1.92 and 3.8, respectively. I n the results for coconut oil the individual results were not so close nor did they show so definite an order in the very meager, if any, influence of the solvent as manifested itself in the cottonseed oil results. The values obtained for cottonseed oil using chloroform are higher and more consistent than those obtained with carbon tetrachloride. The chloroform used was an ordinary stock sample with no special treatment, so that if small amounts of alcohol were present in this reagent its influence was not very marked. I n view of results obtained with alcohol as a solvent, there appears to be no alcohol in the chloroform. ETHYLALcoHoL-lVhen ethyl alcohol was used for the solvent very marked irregularities occurred in the iodine values for both oils. With both oils even the large volumes of alcohol would not completely dissolve the sample. The variations in the values obtained in the individual tests with cottonseed oil were from 74.0 to 98.6 with 25 and 5 cc., respectively, of the solvent. The values were greater with smaller quantities of the solvent. With coconut oil the values were less than one-third of those obtained with carbon tetrachloride or chloroform ranging from 1.23 to 3.82. The sample of back-titrated cottonseed oil produced a brown, gummy mass in the bottom of the bottle. A chemical reaction of some kind produces a retarding effecton the iodine values of cottonseed and coconut oils when alcohol alone is used as the solvent for the oils. This is being studied further 9
Van Nostrand's Chemical Annual, 6 t h issue, 1922, p. 116.
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in the laboratory. It is patent that the presence of alcohol lends itself to variation in results. BENZENE-lvith benzene the results obtained were low and erratic, approximating those of the alcohol solvent with cottonseed oil and those of the ether solvent with coconut oil. The variations ranged from 81.7 to 90.5 for cottonseed oil and from 5.00 to 8.50 for coconut oil. Increased volume of solvent showed no uniform effect. ETHER-The results for cottonseed oil with ether as the solvent were fairly consistent, but not so for the coconut oil, The results are slightly higher than those obtained with benzene but of the same order of influence. These solvents show little material influence on cottonseed oil in increasing their volumes, but much lower results were obtained when the maximum amount of solvents were used, the highest results with these solvents being with 15 cc. Clear and distinct end points were difficult to obtain with ether, probably due to nonuniform solvent evaporation or an inhibiting influence of the ether on the reaction. On standing less than 1 minute, from one to two drops of thiosulfate were required to discharge the color for an end point that remained clear after 1 minute's duration. The extent to which additional thiosulfate was required to discharge the blue c o l o ~was greater the lower the iodine value. The average results are shown in Curves 1 and 2. CONCLUSIONS Chloroform, carbon tetrachloride, alcohol, ether, and benzene all affect the iodine values of cottonseed or coconut oils, the magnitude of their influence varying widely. On cottonseed oil increased solvent above a small amount shows no great effect. It is evident that benzene, ether, and ethyl alcohol cannot be substituted as solvents in the iodine determinations. The uniformity of results in cottonseed oil evaluations with chloroform as the solvent indicates the superiority of this solvent over carbon tetrachloride and ether; also higher iodine values are obtained in the presence of this solvent. With a low iodine oil, such as coconut oil, the presence of the best solvents, chloroform and carbon tetrachloride, seems to help the reaction but little. They seem to be unnecessary in the case of such small iodine values, although their presence is not detrimental. It is evident that the only solvents that are applicable for iodine determinations are chloroform and carbon tetrachloride, and of these two chloroform is superior. Ac K N OWLED GME NT Acknowledgment is made to the Department of Chemistry of Emory University for permission to carry out this study in its laboratories.
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