ISDI;STRIAL 9 S D ESGINEERISG CHEMISTRY
May, 192T
of p H 7.0, which consists in boiling off one-third of the volume of a good distilled water, and then storing the rernainder out of contact with air, in insoluble glass containers. Although various objections have been raised as to the validity of Dawson’s figure of p H 7.0, the writers have found this water to be a simple and quite satisfactory reference standard for the preparation of bromthymol blue indicator solutions, especially as waters repeatedly so prepared will give identical color readings with the same indicator solution. Accordingly, their method of standardization of bromthymol blue is to dissolve the indicator in “Dawson)’ water to which successive small amounts of a dilute solution of sodium hydroxide are added, until the indicator solution tested against the water of p H 7.0, as given above, gives a color corresponding to that given by the same indicator solution when tested against a buffer solution of exactly 7.0 pH. By this procedure the
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addition of a fixed and probably inaccurate amount of sodium hydroxide is avoided, and just sufficient is added to bring the dye to the point of neutrality. Conclusion
It is evident that the correct determination of p H values in sugar solutions, especially those which are weakly buffered, is by no means so simple as many have been led to believe. The sources of error become greatly magnified in the case of slightly buffered solutions, but when it is considered that the latter are extremely sensitive t o invertive changes with changes in p H values, the importance of correct determinations of such values becomes quite obvious. Unless full cognizance is taken of such sources of error, it would seem unwise t o attempt refinery control by the colorimetric method for hydrogen-ion concentration.
The Iodine Number of a Commercial California Sardine Oil’ As Determined by the Hanus and the Hubl Methods By Max S. Dunn and B. S. Hollombe UNIVERSITY OF CALIFORNIA AT Los ANGELBS, Los ANGELPS,CALIF
The iodine numbers of commercial oleic acid and of fish and allied oils give ticability of directly five samples of commercial oil from the California iodine numbers that are cone s t i m a t i n g the unsardine, Sardinia caerulea, have been determined. sistently ten point,s loarer by saturated fatty acids in oils, Closely agreeing values were obtained for oleic acid and the Hanus method than by methods for their indirect defor each sample of oil. It is concluded that the iodine the Wijs procedure, led to the values S O obtained are a reliable index to the relative present investigation. termination have been devised. The addition of halounsaturation of sardine oil and evidence is advanced in Although certain authors4 gens to unsaturated bodies is support of this conclusion. The average value for the hold that the results obtained the basic principle of s u c h iodine number of commercial oil from the California are discordant, a careful conprocedures. A complete dissardine, Sardinia caerulea, was found to be 177.8. sideration of the data leads to cussion of this question has the conclusion that many of been presented by Lewkowitsch.2 Thus it is well known the differences noted are of little significance. Other workers5 that the direct addition of halogens to such unsaturated find that concordant results are obtainable and believe-that bodies is inadequate because of the formation of substitution the values obtained furnish reliable characteristics for fat and products. Slthough various investigators have attempted t o oil analysis. I n the present investigation i t seemed desirable to make a determine the absorption due to substitution and to addition, the values for the latter show little agreement with those ob- careful comparison of the iodine values obtained by the use tained by other methods. of two of the methods previously mentioned. At the same The percentage of iodine taken up by an oil, known as time a study of the relative unsaturation of oil from the sarthe iodine number, is now commonly determined by the dine, Sardinia caerulea, was undertaken. methods of Hubl, Wijs, and Hanus. The first two authors Experimental use iodine chloride as the act.ive substance, while iodine broSamples of sardine oil from the Sardinia caerulea were mide is employed by Hanus. An important objection t o Hubl’s solution is its instability. obtained in March, 1926, from the Van Camps Seafood, Inc., The most apparent advantages inherent in the use of iodine reduction plants located a t Terminal Island, California. halides include their rapid absorption by most oils, their I n each case composite liter samples of oil were obtained negligible absorption by saturated fatty acids, and their from sardines caught about 34 hours previously. The crude absorption in theoretical quantities by certain unsaturated sardine oil is prepared from the offal and any whole fish in fatty acids. It has been further noted that normal iodine excess of the amount required by law to be used for canning values are obtained only if the double bond is distant from Harvey, J . Soc. Chem. I n d . . 21, 1437 (1902); Tolman and Munson, the carboxyl, that trebly linked pairs of carbon atoms readily J . A m . Chem. Soc., 26, 244 (1903); Archhutt, J . Soc. Chem. I n d . , 23, 306 absorb only two halogen atoms, and that cyclic unsaturated (1904); Kreikenbaum, THISJOURNAL, 2, 205 (1910); Schmidt-Nielson a n d Owe, Videnskapsselskapets-Skrifter, 1923, I., M a t e m a t . n a t u r v . Klassc absorb iodine in varying amounts differing from (Kristiania) [ l 5 ] ;C. A , , 18, 2818 (1924); Gillot, Ann. f a l s . , 18, 335 (1925); the theoretical. C. A.,19, 2881 (1925). H u n t , J . SOC.Chem. I n d . , 21, 454 (1902); Kelber a n d Rheinheimer, The recently reported observations of Lange,3 that analyses
WISG to the iniprac-
0
Received January 8, 1927. “Chemical Technology and Analysis of Oils, F a t s , a n d Waxes,” Vol. I, p. 402, hfacmillan a n d Co., Ltd., London, 1921. 3 THISJOWRSAL, 18,9 (1926). 1
I b i d . , 37, 34.4 (1918); Hildt, Reo. p r o d . chim., 21, 254 (1918); C . A , , 12, 2699 (1918); Sundherg a n d Lundborg, Z . Nahr. Genzrssm.. 39, 87 (1920); C. A . , 14, 2537 (1920); Lewkowitsch, o p . c i ~ p. , 410;Kerr. J . Assoc. O f i c i a l A R ~Chem., . 6, 178 (1922); C . A , , 16, 1875 (1922); Bonney, et al , Proc. A m , Soc. Testing .tfaterials. 24, I , 432 (1024): C . .4., 19, 1782 (1925).
I N D U S T R I A L AND ENGIYEERING C H E M I S T R Y
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T'ol. 19, K O . 5
purposes. The water and oil mixture, removed by presses With the exception of sample 1, the figures obtained for the from the thoroughly steamed material, is heated in settling sardine oil are in close agreement. KOexplanation is offered tanks to temperatures ranging from 155" to 200" F. After to account for the low values found for sample 1. The deseparating the oil from the mater, the oil is thoroughly viations from the mean iodine value found for four of the dried by spraying it over coils of steam-heated pipes. This samples of sardine oil by the four procedures agree as closely process causes a slight darkening of the product. The as might be expected for a mixture as complex as that under samples of oil used for analysis varied in color from yellow t o investigation. It would seem, therefore, that iodine values dark brown and contained a considerable proportion of sus- obtained by the Hubl and the Hanus methods are a reliable index to the relative unsaturation of sardine oil. That the pended solids. I n all cases iodine numbers were determined in triplicate Rijs procedure would give comparable results does not logby the Hubl and the Hanus methodsU6 Commercial oleic ically follow, although the fact that the Hanus and the Wijs acid and five samples of sardine oil were investigated. The methods have been found to give the same iodine numbers results of these analyses are given in Tables I, 11, and 111. with a wide variety of oils by the analysts of the Association Detailed analytical data are given only for oleic acid and for of Official Agricultural Chemists gives support to this vielT-. The average value for the iodine number of four samples sardine oil, sample 1. The figures for the other samples are of oil from the sardine, Sardinia caerulea, was found to be similar in all respects to those reported for sample 1. 177.8. Since the figures obtained for sample 1 are much Table I-Iodine N u m b e r s of C o m m e r c i a l Oleic Arid lower than those reported for the other four samples, the THIOSULFATE former data were neglected in obtaining the average value. EQWIV. TO ABSORPTION WEIGHT O F IODISE IODINE Using the Hanus method, Dill7has recently obtained an averMETHOD TIME OIL ABSORPTION h'UMBER age iodine number of 177.5 for four commercial samples of Gram cc. 84.6 0.2260 13.77 Hub1 3 hours oil from the California sardine, Sardinia caerulea. 14.21 84.9 3 hours 0.2324 Htibl Since the objections cited earlier in this paper are probably 14.08 84.8 3 hours 0.2306 Hubl 4 v . 84.8 of negligible importance, here, it seems reasonable to expect 0.2107 12.93 8R. 2 Hub1 4 hours that trustworthy iodine numbers should be obtained for 0,2216 13.53 84.8 Htibl 4 hours 13.77 85.3 4 hours 0,2242 Hub1 sardine oil. Furthermore, recent investigations*have shown Av. 8 5 . 1 that the principal unsaturated fatty acids of fish oils are those 12.84 83.9 30 minutes 0.2126 Hanus containing 14, 16, 18, 20, and 22 carbon atoms; that no 12.07 84.4 30 minutes 0.1987 Hanus 0.2024 12.29 84.2 Hanus 30 minutes double bonds occur in these acids prior to the 9, 10 position; Av. 8 4 . 2 and that the high degree of unsaturation of the longer chain 84.1 0.2310 13.99 Hanus 40 minutes 14.02 83.7 40 minutes 0.2327 Hanus members is due to as many as six double bonds occurring a t 13.06 84.6 40 minules 0.2144 Hanus regular intervals further distant from the carboxyl than, the Av. 8 4 . 1 9, 10 carbon atoms. Although unsaturated acids having Table 11-Iodine N u m b e r s of Sardine Oil, S a m p l e 1 double bonds adjacent to the carboxyl give low iodine values, THIOSULFATE EQUIV.T O oleic acid with a 9, 10 carbon double bond gives normal ioABSORPTION WEIGHT O F IODINE IODINE METHOD TIME OIL ABSORPTION NUMBER dine numbers. Thus it is probable that double bonds still Cram CC. further distant from the carboxyl than the 9, 10 position 31.10 161 4 0 2676 Hub1 3 hours would also react normally. 168 9 0.2402 29.21 Hubl 3 hours 0.2196 26.52 167.7 The following iodine numbers have been reported for other Hubl 3 hours Av. 1 6 6 . 0 related species : Japanese sardineg (Clupanodon melanosticta), 29.49 169.2 4 hours 0.2421 Hub1 180 to 187; European sardinelo (Clupea surdinus), 160.9 0.2390 28.45 165.3 Hiibl 4 hours 0.2117 25.58 169.8 Hiibl 4 hours to 191.7; Clupea harengus,ll 123.5 to 142; and Clupea pilAv. 1 6 8 . 1 chardus,12 170.4 to 172.7. These data indicate that these 0.2386 29.45 171.4 Hanus 30 minutes related species possess a different proportion of unsaturated 0,2122 25.60 167.6 Hanus 30 minutes 0.2187 26.17 166,2 Hanus 30 minutes fatty acids than does Sardinia caerulea. Av. 1 6 8 . 4 Hanus Hanus Hanus
40 minutes 40 minutes 40 minutes
0.2504 0.2261 0.2493
29.71 27.58 30.37
164,s 169.4 169.2 Av. 1 6 7 . 8
Acknowledgment
The authors are indebted to C. B. Andrews, of the Cali-
fornia Fish and Game Commission, Terminal Island, Caliof Data o n Iodine N u m b e r s of Sardine o i l Samples fornia, for the collection of the samples of sardine oil used hhx. HCBL HANUS DEVIATION in these experiments. DATE 3 4 30 45 AVERFROM min. mln. AGE ~ ' ~ E A N SAMPLE COLLECTEDhours hours 7 Ecology, 7, 221 (1926). Per cent *Brown and Beal, J . Am. Chem. Soc., 46, 1289 (1923); Milligan, 165.7 168.1 1 6 8 . 4 l67.8b 1 6 7 . 5 1.2 1 March 4 Knuth, and Richardson, Ibid., 46, I57 (1924); Armstong and Hilditch, 0.9 177.7 180.6 1 7 9 . 4 1 8 1 . 4 1 7 9 . 8 2 March 6 J . Soc. Chem. I n d . , 44, 180T (1925); McGregor and Beal, J. Am. Chem. 2.4 1 7 5 . 3 1 8 2 . 0 1 7 9 . 4 1 8 1 . 1 179.A 3 March 7 Soc., 48, 3150 (1926). 2.1 1 6 9 . 6 172.2" 1 7 7 . 8 1 7 7 . 5 174.3 4 March 8 1.1 176.8 176.6 177.4 179.6 177.6 5 March 9 9 Tsujimoto, J . Coll. Eng., T o k y o I m p . U n i v . , 4 , 1 (1906); J . Soc. Chcm. 1 7 3 . 0 1 7 5 . 9 1 7 6 . 5 1 7 7 . 5 175.7 1.5 AVERAGE I n d . , 26, SI8 (1906). a 5 hours. 10 Lewkowitsch, 00. cit., p. 429. b 40 minutes. 1 1 Lewkowitsch, "The Laboratory Companion to Fats and Oils Industries," p. 48, Macmillan and Co., Ltd., London, 1901. Discussion 1%Laneton. J. Soc. Chem. I n d . . 42. 47T (1923). Table 111-Summary
Previous investigations on oleic acid, which have been found to give normal iodine numbers, are confirmed. All iodine values herewith reported for this acid agree closer than one per cent. Since the sample of oleic acid used was of commercial grade, the iodine numbers do not correspond to the theoretical value. 6 Woodman,"Food Analysis," pp 161 and 164, McGraw-Hill Book Co., N e w York, 1915.
New Drug for Both Syphilis and Leprosy-.$ drug t h a t is designed t o treat both syphilis and leprosy simultaneously has had a successful try-out in Calcutta, according to recent reports. It was developed under the direction of Dr. T. A. Henry at the Wellcome Chemical Research Laboratories in London and consists of a mercury derivative rendered soluble in one of the complex compounds of chaulmoogra oil.
