Determination Of Iodine Value Research Articles

Determination of Iodine Values of Lipids by Bromide Ion Selective Electrode

Abstract A semimicro method for determination of iodine values of lipids is described. An accurately weighed smear of sample (10-20 mg) on a strip of ashless filter paper, 14 × 40 mm, is brominated with bromine vapors for about 5 min. Excess bromine adsorbed on the filter paper is allowed to sublime. Bromine absorbed by the sample is directly related to the degree of unsaturation. Paper with brominated sample is subjected to oxygen flask combustion in the presence of 2 mL 1M sodium hydroxide solution and 10 mL water as absorbing liquid. Bromide formed, which is equivalent to unsaturation, is determined by bromide ion selective electrode. Bromide ions can be also determined by gravimetry or by indirect argentometric titration. The results were statistically analyzed. The iodine values of some fatty acids and oils, determined by this technique, are in accord with those of some officially approved methods.

Potentiometric determination of iodine values of oils with an iodide-selective electrode

Potentiometric determination of iodine values of oils with an iodide-selective electrode

On the Determination of Iodine Value by the Wijs' Method

The processors of oil and fat are in need of a quick determination method of iodine value of oils and fats especially in case of checking the degree of unsaturation of them in the hydrogenation process. Hoffman and Green modified the Wijs' method by employing mercuric acetate as catalyst and made it possible to determine the iodine value of a sample in ten minutes or so. Mercuric acetate, however, cannot be empolyed now because the reaction solution is hard to meet the regulation of water pollution and its disposal has become difficult.Authors have investigated other methods of quick determination of iodine value especially for the oils in the hydrogenation process and have found after all the Wijs' method could be appropriate by only shortening the reaction time to three minutes for the oils of the iodine value less than about 100. This quick Wijs' method gives almost equivalent value of Hoffman's although it tends to give less value than that of the Wijs' method.

Coulometric Titration of Iodine Values in Fats and Oils

AbstractStandard methods for the determination of iodine values of oils involve direct addition of halogen elements to the double bond. Since the reaction proceeds slowly there is a risk of substitution. A direct coulometrical titration method has been investigated.

298. The radiation chemistry of β-pinene

On irradiation with Co/sup 60/ gamma rays, dry BETA -pinene polymerizes in vacuo, to give a product which is partially precipitated from the liquid monomer. The kinetics of the reaction were followed by using dilatometers. At 25--30 deg with a constant dose rate (2.55 x 10/sup 17/ ev g/sup -1/ min-1), polymer formation is linear with time of irradiation up to 60% conversion and the mean yield corresponds to the polymerization of 850 monomer molecules per 100 ev. A decrease in dose rate results in a higher yield per unit dose. The rate shows a positive temperature coefficient in the range -35 to + 55 deg . The polymers are formed with a range of molecular weights and a number-average value of 1360 is obtained for the chloroform-soluble fraction; the insoluble polymer is of higher molecular weight and melts at 220 deg . Infrared and nuclear magnetic resonance spectra together with the determination of iodine values indicate the presence of unsaturated groups in the polymer structure. The polymerization yield is sensitive to the drying technique employed for the monomer and the rate of a dry reaction more » is strongly retarded by added water although the molecular weight of the resultant polymer is unaffected. Evidence of initiator transfer to monomer during the dry polymerization, as well as the marked effect of water, strongly support the participation of ions in the mechanism. A concurrent isomerization of BETA -pinene to dipentene ensues during the polymerization with a yield of 12 molecules per 100 ev; other isomers are also formed in comparable yields. (auth) « less

24—Method for Determining the Iodine Value of Fatty Extracts of Wool

A method is described for the determination of iodine values of oils and fatty extracts from wool by bromine absorption using between 0.02 g and 0.05 g of fatty matter. This method can be used in conjunction with the W.I.R.A. rapid extraction unit.

Countercurrent Distribution of Milk Fat Triglycerides

Summary The purpose of this study was to investigate the application of countercurrent distribution to the separation of milk fat triglycerides. Of the solvent systems tested, the most satisfactory was a 12:7:5 mixture of pentane, 2-nitropropane, and nitromethane. The distributions were followed gravimetrically and by determination of iodine values and saponification equivalents of selected fractions or groups of fractions. The fractionation was influenced by degree of unsaturation and molecular weight of the triglycerides. Although useful separations were obtained with 100 stages, better resolution was achieved by applying the technique to samples previously separated from milk fat by crystallization from pentane at low temperatures. The +4° C. precipitate and −53° C. filtrate were fractionated by countercurrent distribution, and the fatty acids in selected fractions were determined by ultraviolet spectrophotometry and gas-liquid chromatography. Evidence was obtained that there is some degree of selectivity of fatty acids during the formation of milk fat. From the analysis of the +4° C. precipitate, the evidence seems clear-cut that a small amount of tripalmitin is present in addition to dipalmitostearin and dipalmitomyristin. In the −53° C. filtrate, the monoethenoid acids are associated with the higher molecular weight saturated acids, whereas the polyethenoid acids are associated with the lower molecular weight saturated acids.

Technics for separation of plasma cholesterol esters for determination of iodine value, and of cholesterol.

1. A method for quantitative chromatographic separation of cholesterol esters from other blood lipids is presented. 2. A colorimetric micromethod for determination of the iodine number of plasma lipid is described. 3. A more stable reagent and a more stable color reaction than the Liebermann-Burchard reaction for the determination of plasma cholesterol is presented. 4. Employment of the above methods, together with determination of total lipids by the method of Bragdon, permits determinations of net unsaturation of the fatty acids esterified with cholesterol in the plasma.

The Dissolution of Vulcanized Rubbers and Its Bearing on Problems of Rubber Analysis

Abstract Dissolution of a sample of vulcanized rubber is a necessary preliminary to several analytical procedures, e.g., the determination of iodine value or total fillers. If an infallible and convenient agent were available for this process, then doubtless other analytical procedures would be possible of development or improvement and examination of infrared transmission spectra of vulcanized samples would prove a feasible means of identification. Although decalin and nitrobenzene have been widely and satisfactorily used for natural rubber (polyisoprene), there have been several references in the literature to difficulties encountered with the most widely used synthetic rubber, GR-S. Devices to overcome these difficulties include comminution on a roller mill, swelling the sample in strong swelling agents before transferring to the solvent to be used for the dissolution, and grinding on a rubber mill with a plasticizer. All these must be regarded as being of the nature of palliatives, knowledge of the nature of the dissolution process being the real need before the best condition for carrying it out can be decided on. It is shown in this paper that the process is essentially oxidative in nature and, provided that the solvent and rubber are miscible at the temperature of the dissolution, temperature and efficient aeration are the most important rate-determining factors. The nature of the solvent is, of course, of importance with respect to the analytic procedure attempted as all solvents are not suitable for iodine value determination.

Isolation of natural arachidonic acid as its methyl ester

SummaryFresh beef suprarenal glands were ground and extracted thoroughly with alcohol and then with ethyl ether. After removal of solvent the total lipid residue was saponified, and the fatty acids were recovered by extraction. The less unsaturated acids were removed by crystallization from acetone at −40°C. At this stage the filtrate contained essentially all the arachidonic acid originally present in the glands and also unsaponifiable matter. After the unsaponifiable material was removed, the arachidonic acid content of the concentrate was about 25%. These unsaturated acids were converted to their methyl esters and fractionated on a silicic acid adsorption column. The progress of the adsorption fractionation was followed by spectrophotometric examination and determination of iodine values of the eluted fractions. Methyl arachidonate of 90% purity was obtained by this means. It was further purified by fractional distillation in vacuo. The final product had an iodine value of 316.1; theory, 318.8. The purity of this preparation was further established by spectrophotometric examination, by saponification equivalents, mean molecular weight, and by x‐ray diffraction patterns and melting points of a completely hydrogenated portion.Evidence of acids of greater unsaturation than arachidonic acid in suprarenal lipids was also clearly established by spectrophotometric examination. A fraction was obtained which was estimated to contain about 80–85% of a C20 acid with five double bonds.

(161)洗剤原料油脂のカウフマン法に依る沃素價測定について

(161)洗剤原料油脂のカウフマン法に依る沃素價測定について

Rapid method for the preparation of samples and evaluation of oil quality in small samples of flaxseed

1. One-gram samples of flaxseed, such as are obtained from single plants in breeding work, may be prepared rapidly in quantity for iodine value estimation of oil quality by grinding in an intermediate Wiley mill and partially extracting immediately on a filter with petroleum ether. 2. The oils obtained after evaporating and drying the extract are sufficient in quantity to permit the determination of iodine value either refractometrically or by a modified Wijs method in which the oil sample is measured by a precision pipette involving a special technique.

Fatty acid analyses of known mixtures of purified methyl esters

Mixtures of known composition of purified methyl esters of lauric, myristic, palmitic, stearic, oleic, linoleic and linolenic acids have been prepared. Fractional distillation under reduced pressure followed by spectrophotometric determination of methyl linoleate and methyl linolenate in each of the fractions and determination of iodine values and saponification equivalents allowed calculation of the compositions which agreed well with the compositions of the original mixtures.

Rubber, Polyisoprenes, and Allied Compounds. VI. The Mechanism of Halogen-Substitution Reactions, and the Additive Halogenation of Rubber and of Dihydromyrcene

Abstract The chlorination of cyclohexene by chlorine or by sulfuryl chloride (in the absence of a peroxide catalyst) yields substituted as well as additive chlorination products, and the former retain in full the original olefinic unsaturation, as indicated by iodine-value determination ; but whereas sulfuryl chloride forms only the additive dichloride and a monochloroölefin which is substituted exclusively in the 3-position, chlorine yields a mixture of saturated trichloro derivative (chloro-substituted addition product) and isomeric monochloroolefins (3- and 4-substituted), with some additive dichloride. No evidence of substitution at the ethylenic methine carbon atom has been obtained in the chlorination of cyclohexene, dihydromyrcene, and rubber by chlorine. The diminished unsaturation of the chloro-substitution products of the last two hydrocarbons is attributed to cyclization—a process which is complete in the case of rubber, but affects only a minor proportion of the molecules of dihydromyrcene. The same cyclizing tendency appears in the substitutive bromination of rubber by N-bromosuccinimide, but not to any appreciable extent in the similar bromination of dihydromyrcene. Additive chlorination products are formed when rubber is brought into reaction with chlorine liberated by the thermal dissociation of phenyliododichloride, or of sulfuryl chloride in the presence of a peroxide. The mode of reaction of bromine with rubber, about which many contradictory statements have been made, is found to be entirely additive if the solvent contains a trace of alcohol and the temperature is 0°. A method based on bromine addition may be used for estimating rubber hydrocarbon. Additive bromo and chloroderivatives of rubber are comparatively stable, and give no indication of the spontaneous elimination of halogen acid, either through cyclization reactions or the reformation of double bonds at temperatures up to 80°. The provision of chlorine in free-radical form appears to be an essential condition for obtaining the wholly additive chlorination of rubber and allied olefins. The reaction of molecular chlorine or bromine, on the other hand, follows a course which can be adequately explained by the initial formation of an activated dihalide, the fate of which is determined by the nature of the olefinic system and the experimental conditions.

43. Rubber, polyisoprenes, and allied compounds. Part VI. The mechanism of halogen-substitution reactions, and the additive halogenation of rubber and of dihydromyrcene

Abstract The chlorination of cyclohexene by chlorine or by sulfuryl chloride (in the absence of a peroxide catalyst) yields substituted as well as additive chlorination products, and the former retain in full the original olefinic unsaturation, as indicated by iodine-value determination ; but whereas sulfuryl chloride forms only the additive dichloride and a monochloroolefin which is substituted exclusively in the 3-position, chlorine yields a mixture of saturated trichloro derivative (chloro-substituted addition product) and isomeric monochloroolefins (3- and 4-substituted), with some additive dichloride. No evidence of substitution at the ethylenic methine carbon atom has been obtained in the chlorination of cyclohexene, dihydromyrcene, and rubber by chlorine. The diminished unsaturation of the chloro-substitution products of the last two hydrocarbons is attributed to cyclization—a process which is complete in the case of rubber, but affects only a minor proportion of the molecules of dihydromyrcene. Th...

FATTY ACIDS AND THEIR ESTERS: III. IODINE VALUES BY THE BROMINE VAPOR METHOD

A modified bromine vapor method for iodine value determination that allows of the determination of substitution is described. For non-conjugated unsaturated oils free from oxidation or polymerization products, values are obtained that are in close agreement with those found by Wijs' method. The unsaturation of conjugated esters can be determined satisfactorily. Owing to substitution, the unsaturation of oxidized or polymerized esters cannot be determined by this method.