Acid content test

Very few plastics have a corrosive characteristic that may contain acids and erode tubing. An acid content test can be conducted by determining their pH factor. A pH of 7 is neutral. Any reading below 7 is an indication of acid. A pH reading above 7 would indicate that the material is alkaline. Powdered materials with strong acid indications will have to be conveyed through special pneumatic systems in order to prevent any corrosion from taking place within the system. 

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. 

Analytical and Test Methods. Measurement of the sohdification point using a highly sensitive thermometer and of APHA color by comparison of molten samples to APHA standards is straightforward. Specific impurities are measured by gas chromatography. A nonaqueous titration is used to determine phthahc acid content. 

Tomato fruits (Lycopersicon esculentum Mill. var. Castlemart ) were collected from vines grown in the field at the University of California, Davis. Pericarp discs were cut from surface sterilized MG stage fruit (10). Droplets (10 n ) of test solutions (see below) were applied to the cut surface of discs and disc ethylene production was measured as described previously (11). The amounts of test materials used were based on colorimetric assay (6) of uronic acid content. 

Crops with high acid content have to be tested separately, to demonstrate the robustness of methods with regard to changes in pH. In such cases, where extractions are performed at pH values which are lower than those of acidic crops (e.g., <3), the influence of sample acidity is not significant. It is assumed that under such circumstances an expert statement should be sufficient and may replace validation experiments with representative commodities of this matrix group. 

In studies on test meals, Walker et al. (32) discovered that the calcium of Swiss chard, which has a high oxalic acid content, was poorly absorbed. Children excreted more calcium during the 6 hours after a test meal of milk, Pumpkin leaves, cassava leaves, or pigweed leaves than after Swiss chard. All supplements contained 200 mg calcium. 

In the laboratory for the electroplating facility at Molex, Inc., Lincoln, Nebraska, seventeen plating baths set up for tin and tin-lead electroplating must be tested three times daily for acid content. The procedure involves an acid-base titration using standard sodium hydroxide as the titrant. Because the volume of samples is so large, an automatic bottle-top buret is used with a 2-gal bottle filled with the standard sodium hydroxide solution. 

It is well recognised that the faecal bile acid content of random stool samples is highly variable with marked daily variation.Therefore, studies testing the association between luminal bile acid exposure and the presence of colorectal neoplasia have usually measured serum bile acid levels, which demonstrate less variability and are believed to reflect the total bile acid pool more accurately. Serum DCA levels have been shown to be higher in individuals with a colorectal adenoma compared with individuals without a neoplasm. Only one study has assessed future risk of CRC in a prospective study of serum bile-acid levels. The study was hampered by the small sample size (46 CRC cases). There were no significant differences in the absolute concentrations of primary and secondary bile acids or DCA/CA ratio between cases and controls although there was a trend towards increased CRC risk for those with a DCA/ CA ratio in the top third of values (relative risk 3.9 [95% confidence interval 0.9-17.0 = 0.1]). It will be important to test the possible utility of the DCA/ CA ratio as a CRC risk biomarker in larger, adequately powered studies. A recent study has demonstrated increased levels of allo-DCA and allo-LCA metabolites in the stool of CRC patients compared with healthy controls. ... 

The water content of benzoic acid is tested according to USP general test <921>, Method I, using a 1 in 2 solution of methanol in pyridine as the solvent. Not more than 0.7% water can be present. 

Mercury fulminate prepared by one of the methods outlined above is tested to check the acid content and the content of other mercury compounds. When tested with litmus paper, the moist product should give a neutral reaction. A 5 g test sample mixed with 2 g of sodium hydrogen carbonate should not give a black or bluish tint. 

Nitrating temperature Residual acid content Heat test... 

The current method (3, 4, 6, 22) involves steam distillation to separate the volatile (primarily acetic) acids from the non-volatile (fixed) acids. Special equipment has been devised for this separation (6). Sulfurous and sorbic acid content can be corrected, or the sulfurous acid may be removed (33). Carbon dioxide must be removed so that it does not interfere with the test (6, 33). An automated procedure is also available (34) which measures the volatile acids in the distillate at 450 nm using bromophenol blue. 

CoQumonc Coenzyme Qm Alpha Lipoic acid The test of the content composition and entire shell composition arc not known ... 

The Ge-ZSM-5 catalysts have also been screened in other test reactions [67]. In general, materials with high germanium content appeared to suffer to a much smaller extent from deactivation than samples with lower germanium levels for most of the acid-catalyzed reaction studied. In this way it was shown that the difference in catalytic performance originates from the presence of Ge in these samples and that the improved catalytic stability is similar in several acid-catalyzed test reactions. 

It may also be necessary to determine the free fatty acid content of oily materials as an index of rancidity, since this will affect palatability. Analyses of amino acids can only be conducted in specialized laboratories and are conducted less frequently. Instead most feed mixers (including commercial feed manufacturers) use procedures such as prediction equations based on the protein content of the sample to predict the content of important amino acids. Tests for minerals are more routine and are offered by most laboratories. Tests for vitamins are offered by certain laboratories but are not very frequent since commercial feed manufacturers often disregard any vitamin contribution from the dietary ingredients and add all the necessary vitamins in the form of a supplement. 

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