Standard methods of solvent analysis

Amine acid acceptance by halogenated solvents is the degree to which an amine is capable of absorbing or neutralizing acid present from an external source or generated by the solvent. This method is useful for comparing the effect of an amine with other acid-accepting compounds. The test is performed by the titration of an alkaline water extract from the solvent with 0.2 N hydrochloric acid to pH = 3.9 as detected by pH electrode. 

The alkalinity of acetone is determined by a titration with 0.05 N H2SO4 in the presence of methyl red indicator. The test method provides a measure of acetone alkalinity calculated as ammonia. 

The acidity of halogenated solvents can be determined by titration with 0.01N sodium hydroxide in the presence of a 0.1 % solution of bromophenyl blue indicator. Similar to the determination of alkalinity, acidity is determined in water extract. The determination can also be done directly in solvent but the solution of sodium hydroxide should be prepared in methanol. A third option is to determine acidity by a pH-metric titration of a water extract. Prior to determination, the pH of solvent is measured. If the pH is above 7, then an alkalinity measurement is done by the above method. If the pH is below 7, acidity is determined by this method. The method is used to establish purchasing and manufacturing specifications and control the quality of solvents. 

The acidity of benzene, toluene, xylenes, naphthas, and other aromatic hydrocarbons is determined by the titration of a water extract with 0.01 N sodium hydroxide in the presence of 0.5% phenolphthalein indicator solution. The method is suitable for setting specifications, internal quality control, and development of solvents. The result indicates the potential corrosivity of solvent. 

The acidity of solvents used in paint, varnish, and lacquer is determined by the titration of solvent diluted with water (for water soluble solvents) or isopropyl alcohol or ethanol (for water insoluble solvents) in proportion of 1 1. A water solution of 0.05 N sodium hydroxide in the presence of 0.5% phenolphthalein indicator dissolved in ethanol or isopropanol is used for titration. The method is usefirl for determination of acidity below 0.05%. Acidity is a result of contamination or decomposition during storage, transportation or manufacture. The method is used to assess compliance with specification. 

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