Acid content

Table 8.15 gives the acid content of some crudes. 

To determine the exact perbenzoic acid content of the solution, proceed as follows. Dissolve 1 -5 g. of sodium iodide in 50 ml. of water in a 250 ml. reagent bottle and add about 5 ml. of glacial acetic acid and 5 ml. of chloroform. Introduce a known weight or volume of the chloroform solution of perbenzoic acid and shake vigorously. Titrate the liberated iodine with standard O lA sodium thiosulphate solution in the usual manner. 

To determine the per-acid content, add 30 ml. of 20 per cent, po assium iodide solution to 2-0 ml. of the solution and, after 10 minutes, titrate the liberated iodine with standard 0-05N sodium thiosulphate solution (compare Perbemoic Acid, Section IV,198, Note 1). 

The impurity is potassium chloride. The approximate acid content is determined by heating a weighed sample of the acid in a crucible gently at first and finally at a red heat until no trace of black residue remains, and weighing the white residual potassium chloride. 

Acid content calculated as tartaric acid is about 6—7 g/L for best flavor and stabiUty. It is higher for tart low Brix musts and less important for sweet high Brix musts. High acid levels coiacide with a higher level of the second acid of grapes, malic acid. 

Acidity is determined by glc or titration, and the dimer content of acryhc acid by glc or a saponification procedure. The total acidity is corrected for the dimer acid content to give the value for acryhc acid. 

Properties. Important properties of NSP are free acid content, as H2SO4, 1—2% moisture content, 5—8% P2O5 soluble, in neutral citrate... 

Specific Gravity. Fiber cross sections are often irregular and specific gravity is measured by an immersion technique. The values of 1.32 for acetate and 1.30 for triacetate are accepted for fibers of combined acetic acid contents of 55 and 61.5%, respectively (13—15). 

Processes for Triacetate. There are both batch and continuous process for triacetate. Many of the considerations and support faciUties for producing acetate apply to triacetate however, no acetyl hydrolysis is required. In the batch triacetate sulfuric acid process, however, a sulfate hydrolysis step (or desulfonation) is necessary. This is carried out by slow addition of a dilute aqueous acetic acid solution containing sodium or magnesium acetate (44,45) or triethanolamine (46) to neutrali2e the Hberated sulfuric acid. The cellulose triacetate product has a combined acetic acid content of 61.5%. 

In the batch methylene chloride process, the sulfuric acid concentration can be as low as 1% and only limited desulfonation is required to reach a combined acetic acid content of 62.0%. With perchloric acid catalyst, the nearly theoretical value of 62.5% combined acetic acid is obtained. 

The free sulfur trioxide can be titrated with water the end point is deterrnined conductimetricaHy. The sulfuric acid content is deterrnined from the specific conductivity of the Hquid at the point in the titration where no free SO or excess water is present. If the presence of HF is suspected, a known amount of SO is added to the acid and the excess SO is deterrnined as above. The content of another common impurity, SO2, may be determined iodometricaHy in a dilute, aqueous solution. 

Table 7. Amino Acid Content of Nonphotosynthetic Microorganisms Grown on Various Substrates, g/16 g N ...

Nucleic acid contents of SCP products, which range up to 16% in bacteria and 6—11% in yeasts, must be reduced by processing so that intakes are less than 2 g/d to prevent kidney stone formation or gout. Adverse skin and gastrointestinal reactions have also been encountered as a result of human consumption of some SCP products (87). 

LPC Product Quality. Table 10 gives approximate analyses of several LPC products. Amino acid analyses of LPC products have been pubhshed including those from alfalfa, wheat leaf, barley, and lupin (101) soybean, sugar beet, and tobacco (102) Pro-Xan LPC products (100,103) and for a variety of other crop plants (104,105). The composition of LPCs varies widely depending on the raw materials and processes used. Amino acid profiles are generally satisfactory except for low sulfur amino acid contents, ie, cystine and methionine. 

The sulfur amino acid content of soy protein can be enhanced by preparing plasteins from soy protein hydrolysate and sources of methionine or cystine, such as ovalbumin hydrolysate (plastein AB), wool keratin hydrolysate (plastein AC), or L-methionine ethyl ester [3082-77-7] (alkaU saponified plastein) (153). Typical PER values for a 1 2 mixture of plastein AC and soybean, and a 1 3 mixture of alkah-saponified plastein and soybean protein, were 2.86 and 3.38, respectively, as compared with 1.28 for the soy protein hydrolysate and 2.40 for casein. 

The alginic acid content of some of the commercially important brown algae is shown in Table 4. The commercial processes for the production of algin are proprietary (22,23). 

Wine Making. Wine making is one of the principal areas of tartaric acid use. There is a relationship between the size of the grape crop and its tartaric acid content when grapes are pressed. In poor harvest years, the tartaric acid content is low in good harvest years, the tartaric acid content is high. Thus, in poor harvest years, tartaric acid often is added to correct acid deficiencies in wine. 

Humic acids are alkaH-extractable materials and total humic acid content is a term that refers to the humic acid content of coal that has had its carboxylate cations removed with sodium pyrophosphate. Values for some typical AustraHan brown coals range from 24—92% (13). Treatment of lignitic coals with mineral acid to release the alkaH and alkaline cations may dissolve up to 20% of the coal. The naturally moist coals are slightly acidic and have a pH of 3.5—6.5. 

The test methods used by industry to determine if a sample of maleic anhydride is within specifications (165) ate ASTM methods D2930, D1493, and D3366. These methods describe procedures for the determination of maleic acid content, the crystallization point, and the color properties of the maleic anhydride sample, respectively. By quantitative deterrnination of these properties, a calculation of the overall purity of the maleic anhydride sample can be made. 

The free maleic acid content in maleic anhydride is determined by direct potentiometric titration (166). The procedure involves the use of a tertiary amine, A/-ethylpipetidine [766-09-6J, as a titrant. A tertiary amine is chosen as a titrant since it is nonreactive with anhydrides (166,167). The titration is conducted in an anhydrous solvent system. Only one of the carboxyhc acid groups is titrated by this procedure. The second hydrogen s dissociation constant is too weak to titrate (166). This test method is not only used to determine the latent acid content in refined maleic acid, but also as a measure of the sample exposure to moisture during shipping. 

Naphthenic acids are normal constituents of nearly all cmde oils, but not all cmdes contain sufficient quantities of usable acids to make recovery an economic process. Heavy cmdes from geologically young formations have the highest acid content, and paraffinic cmdes usually have low acid content. 

The acid content of cmde petroleum varies from 0—3%, with cmdes from California, Venezuela, Russia, and Romania having the highest content. Smaller amounts are found ia U.S. Gulf Coast cmdes, whereas Httie or no naphthenic acids are found ia Pennsylvania, Iraq, or Saudi Arabia cmdes. Typical concentrations are shown ia Table 2. Minor amounts of naphthenic acids are also found ia bituminous oil sands, but these are not economically recoverable. Identification of naphthenic acids ia water from oil-beating strata is being examined as a potential method of petroleum exploration (18). 

Naphthenic acids occur ia a wide boiling range of cmde oil fractions, with acid content increa sing with boiling point to a maximum ia the gas oil fraction (ca 325°C). Jet fuel, kerosene, and diesel fractions are the source of most commercial naphthenic acid. The acid number of the naphthenic acids decreases as heavier petroleum fractions are isolated, ranging from 255 mg KOH/g for acids recovered from kerosene and 170 from diesel, to 108 from heavy fuel oil (19). The amount of unsaturation as indicated by iodine number also increases in the high molecular weight acids recovered from heavier distillation cuts. 

Table 4. Essential Amino Acid Content of Nuts ...

Table 5. Oil and Fatty Acid Content of Commercial Nuts ...

Values for fatty acids are % of total fatty acid content. ... 

The nicotinic acid content of several nuts has been reported (in mg/kg) as follows chestnut, 200 ha2el nut, 600 almond, 1600 and sunflower seed, 5000 (40). The results of analyses for pantothenic acid are (in mg/kg) ha2el nut, 380 almond, 75 sunflower seed, 620 and walnut, 600. Nuts also contain more biotin than most fmits and vegetables. 

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