Wijs method

Thus, the iodine values assayed (calculated) from the alkenyl proton integration and the corresponding molecular weight match quite favourably with the results obtained by Wijs Method as shown below ... 

Iodine Value (or Number)—the percentage of iodine that will be absorbed by a clieimcally unsalurated substance, such as vegetable oil, in a given time under specified conditions. The iodine value is a measure of degree of unsaturation. Two methods are described in the Food Chemicals Codex the Hanus method and the Wijs method. 

American Oil Chemists Society. 1993b. AOCS Official Method Cd 125. Iodine Value of Fats and Oils—Wijs Method. Champaign, 111. 

Additional properties of vinyl laurate are 1.4345 and 2 0.8639. If the iodine number is determined by the Wijs method, a 200% excess of iodine chloride solution and a 1-hour reaction period should be employed in order to obtain values which are 97-99% of the theoretical value. 

Modified Wijs Method (Acetic Acid/Cyclohexane Method)... 

Iodine Value Proceed as directed under Modified Wijs Method, Appendix VII. 

Iodine value (IV) g iodine/100-g sample (WIJS method)... 

The Codex Alimentarius (Codex-Stan 210-1999) indicates the characteristics of crude regular sunflower oil (1) saponification value = 188-194-mg KOH/g oil (2) iodine value (calculated from the fatty acid composition) = 118-141. However, Merrien (9) reports an iodine value of 120-134, and Bockisch (5) reports a value in the range of 110-143 (Wijs method). 

The iodine value of the ester was determined by Wijs method, and was also calculated from the GC-MS mixtures using Equation 1J... 

Determination of iodine value /,) According to the (Wijs) lUPAC (1964) method (lUPAC Standard Methods for the Analysis of Oils, Fats and Soaps, 5th edition, 1966 II.D.7.1., II. D.7.2 and II.D.7.3 The wijs Method). Results are expressed as percentage of mass per mass absorbed iodine. 

Wijs method for iodine values, 259 Winterization, 213 Wittig reaction, 290 Wolman s disease, 548 Wool wax, 19,143 World production, 91,107,130,138 see also individual fats Wrasse, lipids, 131... 

Wijs method Analytical method for determining the degree of unsaturation of a material, which involves the addition of... 

Wijs Method Analytical method for determining the degree of unsaturation of a material, which involves the addition of iodine to the existing double bonds. The iodine is derived from a solution of iodine monochloride in glacial acetic acid. See Iodine Test and Iodine Value Hanus Iodine Number Wilkinite See Bentonite. 

The well-known Wijs method is considerably shorter and is used by the 5.P. Briefly it is ... 

Hanus method, used by the U,S,P, is equivalent to the Wijs method and the same process is followed, thirty minutes being allowed for absorption of all oils and fats except castor, cod-liver and linseed oils, which are allowed to stand for one hour. The Hanus iodobromide solution is made by dissolving 13 2 g of iodine in 1 litre of glacial acetic acid and then, to the cold solution, a quantity of bromine is added equivalent to that of the iodine present the iodine present is determined by titration. 

Another method worthy of mention is the absorption of bromine vapour by thin films of oils and fats, devised by Toms. To obtain quantitative results comparable with the Wijs method only a very thin layer of oil must be used, sufficiently thin to prevent the formation of a pellicle on the surface. The method is extremely simple. 

For the less unsaturated oils larger amounts are needed, and then it is advisable to use a larger plate, with a similar one for a counterpoise. The iodine value is obtained by the factor 1 588 and was shown to agree closely with the iodine value obtained by Wijs method, except for notable differences unassociated with oils of pharmaceutical use, other than castor oil, which gave a lower bromine absorption, probably owing to the presence of ricinoleic acid. The appearance of the film after absorption is in many cases characteristic of the particular oil. 

The methods for determining the iodine value of lipids are Hanus method and Wijs method. The lipid to be analyzed is weighed and dissolved in a suitable organic solvent, to which a known excess of iodine monobromide (or the monochloride) is added. Some of the IBr reacts with the double bonds in the imsaturated lipids, whereas the rest remains unreacted ... 

Procedure Determination of Iodine Number by the Wijs Method (74)... 

The usual procedure for determining unsaturation in quaternaries is the Wijs method, described in Chapter 2. The ASTM test optimized for determination of unsaturation of the alkyl group in fatty quaternary ammonium chlorides is D2078 (12). The corresponding AOCS method is Tg 3a-64 (11). For other compounds, the recommended AOCS method is Cd 1-25 (13). 

The usual procedure for determining unsaturation is the Wijs method, described in Chapter 2. The recommended ASTM and AOCS methods are D2075 and Cd 1-25, respectively (13,14). 

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