Solvents peroxide value

Residual solvents see Section 9.1.3.1 peroxide value mmol peroxide/L. 

Official quality parameters comprise acidity, peroxide value, halogenated solvents, ultraviolet adsorption and sensory assessment. In addition to these official parameters important roles and high values are attributed to the content of the chlorophyll and carotene pigments and phenol antioxidants, as well as to the correlated induction time value. The significance of olive oil quality parameters is explained in Table 2.1. The phenol content and the related induction period, defined as the delay in the commencement of oxidation in an oil , merits particular comment the longer the induction period, the better the oil. Resistance... 

Allow the sample solution to stand, agitating it occasionally, for exactly 1 min, and immediately add 30 mL of water. Titrate with 0.1 A sodium thiosulfate solution, adding the solution gradually while constantly agitating until the yellow iodine color has almost disappeared. Add 0.5 mL of a 10% sodium lauryl sulfate (SDS) solution, and then add approximately 0.5 mL of Starch Indicator Solution. Continue the titration while constantly agitating, especially near the endpoint to liberate all of the iodine from the solvent layer. Add 0.1 A thiosulfate solution dropwise until the blue color just disappears. If the titration is less than 0.5 mL using 0.1 A sodium thiosulfate, repeat the determination using 0.01 A sodium thiosulfate. Conduct a blank determination, and make any necessary correction. Calculate the peroxide value by the formula... 

LOO additions increase with heat (289), extent of oxidation (290), and solvent polarity (266). Dimer levels of methyl linolenate autoxidized neat at room temperature varied from 0.1% to 10.1%, proportional to peroxide values (290). MLn autoxidized at 40°C to PV 1062 gave 6.8% dimers 80% of these were from LOO and 20% were from epidioxide-OO additions. The dimer linkages were mostly C—O—O—C at lower temperatures, but shifted to C—C and C—O—C as the temperature increased (276). At PV = 4002, LOO additions increased to 55% of the products. Epidioxide peroxyl radicals, in particular, showed a very strong tendency to add to double bonds, with greater than 90% dimerization at 40°C. 

A measured amount of fat is dissolved in acetic acid-chloroform solvent in the presence of potassium iodide. Peroxides in the fat liberate iodine, which is titrated with 0.10 N sodium thiosulfate. A blank run is similarly treated. Peroxide value (meq peroxide oxygen/kg oil = (B — 5) x 0.10 A thiosulfate x 1000/g oU where B = titer of blank in mL and S = titer of sample in mL. 

The Codex Alimentarius standard includes limits for acidity, volatile matter, insoluble impurities, peroxide value, colour, odour, taste, iron, copper, K27o, AK, permitted additives, contaminants (lead, arsenic, halogenated solvents), refractive index, saponification value, iodine value and unsaponifiable matter. Physical and chemical constants, such as iodine value and saponification value, are not found in the EU regulation. This is explained by the fact that more definite information is obtained by determining fatty acid composition, sterol and wax composition, trans fatty acid content, stigmastadiene, and so on. 

Approximately 0.3-5 g of sample, depending on the peroxide value expected, is weighed accurately 25 ml of a solvent consisting of a mixture of 2 vol. of acetic acid and 1vol. of trichloromethane is added, after which the air above the liquid is displaced with carbon dioxide or nitrogen. After addition of 1ml of a saturated potassium iodide solution, a homo-... 

The determination of peroxide value is useful for bulk oils that can be analysed directly. For foods, emulsions or muscle tissues, the lipid is extracted with mixtures of solvents that must be carefully removed by evaporation... 

Oxidation. Maleic and fumaric acids are oxidized in aqueous solution by ozone [10028-15-6] (qv) (85). Products of the reaction include glyoxyhc acid [298-12-4], oxalic acid [144-62-7], and formic acid [64-18-6], Catalytic oxidation of aqueous maleic acid occurs with hydrogen peroxide [7722-84-1] in the presence of sodium tungstate(VI) [13472-45-2] (86) and sodium molybdate(VI) [7631-95-0] (87). Both catalyst systems avoid formation of tartaric acid [133-37-9] and produce i j -epoxysuccinic acid [16533-72-5] at pH values above 5. The reaction of maleic anhydride and hydrogen peroxide in an inert solvent (methylene chloride [75-09-2]) gives permaleic acid [4565-24-6], HOOC—CH=CH—CO H (88) which is useful in Baeyer-ViUiger reactions. Both maleate and fumarate [142-42-7] are hydroxylated to tartaric acid using an osmium tetroxide [20816-12-0]/io 2LX.e [15454-31 -6] catalyst system (89). 

The pKs value of acetic acid is about the same as that of water therefore, in order to obtain high accuracy and greater differentiation in potentiometric titrations, Pifer and Wollish91 preferred to use acetic acid mixed with dioxan in the solvent and also in the perchloric acid titrant in view of the possible presence of peroxide, the previous purification requires great care40. Similarly, Fritz92 recommended acetic acid mixed with acetonitrile (pKs = 19.5 at 25° C)93 in both the solution and the titrant. 

The yield of cage reaction products increases with increasing viscosity of the solvent. The decomposition of diacyl peroxides was the object of intensive study. The values of rate constants of diacyl peroxides (diacetyl and dibenzoyl) decomposition (kf and initiation (ki = 2ekd) are collected in Tables 3.4 and Table 3.5. The values of e are collected in the Handbook of Radical Initiators [4]. 

The higher the viscosity of the solvent, the longer the period of time of radical pair existence in the cage and the higher the observed value of scrambling rate constant [3,80-82]. The same phenomenon was observed during the photolysis of benzoyl peroxide and 1,1-dimethylethyl perbenzoate [3]. 

The individual polarographic characteristic of the analyzed compound is the potential El/2 at which the current strength equals 50% of its maximum value. The binary solvent benzene-methanol or benzene-ethanol is used. The amount of peroxide is proportional to the maximum strength of the electric current at peroxide concentration in solution lower than... 

Some examples, such as thermal polymerization of styrene and decomposition of di-f-butyl peroxide, are given in [194], both treated as first-order reactions. The activation energy found for the decomposition of di-f-butyl peroxide agrees well with the literature value. From the pressure data, it appears that the initial pressure rise is caused by the evaporation of toluene, present as a solvent. At higher temperatures, the gases generated by decomposition are the main contributors to the pressure rise. 

Concentrated organic peroxides, such as f-butyl peroxybenzoate (TBPB), have an F value of about 100 to 150 kj/kg. These compounds can produce a runaway ending in a deflagration. Dilution of the peroxide with the proper solvent will result in a considerable decrease of the F value because of the decrease in concentration of the active component and the decrease in the maximum temperature due to heating and evaporation of the solvent. 

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