Hydroxyl value method

Precision The reproducibility of the method likewise must match the needs of the problem. The hydroxyl value method used in the Bulging Drum Problem might not have been precise enough to detect any differences between the good and bad EOs. 

The hydroxyl value (or hydroxyl number) method measures the number of -OH groups on a molecule. The result is reported in milligram of potassium hydroxide titrated by a sample of 1 g size thus it is a measure of both the chain length/molecular weight and purity of a... 

Results for the hydroxyl value determination were inconclusive the precision of the method and the normal range of results for receipts of EO were not significantly different. Combined with the finding of zero for the peroxide value, the oxidation hypothesis seems less likely. Moisture content and pH results were more interesting. Normally, pH readings on the ethoxylate were above 10. The moisture values were somewhat above typical values. These two results do not really support or refute the hypothesis of EO oxidation, but when solving a problem, any unusual or unexpected results are noteworthy. 

Personnel Choosing an appropriate technique sometimes comes down to having the right person on your staff to perform the technique. If you, or no one in the lab, had had experience with the hydroxyl value titration, it might not have been an option in the Bulging Drum Problem. Certainly, if the operator of your triple quadrupole mass spectrometer is on vacation and there is no back-up operator, another method, or sending the samples to another lab, may be necessary. Should the method need to be transferred to another lab, does that lab have the requisite people for the job ... 

Hydroxyl Value Determine as directed in Method II under Hydroxyl Value, Appendix VII. 

The most common method of manufacture involves the hydrolysis of natural vegetable oils such as coconut or palm kernel oil, followed by fractional distillation of the free fatty acids produced. The Cg to Cig fractions are then hydrogenated and reesterified under controlled conditions with glycerin to form a mixture of tri-, di-, and monoglycerides of the required characteristics and hydroxyl value. This process is used for Witepsol. 

ASTM D1957, Standard Test Method for Hydroxyl Value of Fatty Oils and Acids, the Annual Book of ASTM Standards. Vol. 06.03, 2001. 

The analytical methods for the characterization of raw materials and reaction products are given in Table 3. They are mainly standardized methods and most of them are classical. Determinations of polymer content and hydroxyl values were performed to control side reactions such as dimerization and diol formation. 

Polyurethanes are characterised by the conventional analytical and spectroscopic techniques in the same way as other polymers. The standard techniques used for detennining physical properties such as viscosity, specific gravity, drying time, hydroxyl value and isocyanate value (by butyl amine method) have been discussed in earUer chapters. Structural confirmation, molecular weight detennination, rheological behaviour and thermal characterisation are generally carried out by spectroscopic techniques such... 

This method for the determination of the hydroxyl value does not differentiate between hydroxyl groups... 

The method described is comparable to lUPAC method 2.241 (Paquot, 1979a) as well as to the AOCS method Cd 13-60 (AOCS, 1978) although the latter uses different quantities of sample for the various ranges of expected hydroxyl value. The details of the procedure are also slightly different. 

Analytical characteristics of fish oils and whale oils, 134,139 Analytical methods anisidine value, 264 AOCS, 259 dilatation, 253 fat adulteration, 270 fat content, 250 free fatty acids, 260 gas chromatography, 265 hydroxyl value, 261 iodine value, 259 lUPAC, 249 NMR spectra, 250 pancreatic lipase hydrolysis, 267 peroxide value, 263 phosphorus estimation, 264 saponification value, 260 slip point, 251 solid fat, 255 standard, 250... 

Additionally, polyesters and polyethers may contain several impurities derived from their methods of manufacture and being polymeric materials may vary in molecular weight and type of end-group. For routine analysis of raw materials, a determination of hydroxyl value, acid value and water content is usually sufficient. The reactivity of polyesters of the same chemical type can vary widely and for this reason it is sensible that an activity test be performed similar to that for diisocyanates using a diisocyanate of standardized activity. 

ISO 4326 1980 Nonionic surface active agents— Polyethoxylated derivatives— Determination of hydroxyl value— Acetic anhydride method. International Organization for Standardization, Geneva. 

Fleming J. Rapid method for the determination of hydroxyl values. J Cosmet Sci 1966 17 625-630. 

Table 3.1 compares hydroxyl values obtained by three methods. In every case the acid-catalysed acetylation method gives a higher result than that obtained by phthalation, the mean difference between the two methods being 2.5% of the determined value. Agreement between the p-toluene sulfonic acid method and the phenyl isocyanate method is good. 

Molecular weight p-Toluene sulfonic acid-catalysed acetylation method. Average hydroxyl value (mg KOH/g) Phthalation method. Average hydroxyl value (mg KOH/g) Reaction with phenyl isocyanate. Average hydroxyl value (mg KOH/g)... 

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