Benzoic acid neutralization analysis

Prepn. Dissolve 2.4g of Pb nitrate in 50ml w at 90—95°, and add with stirring a coned soln of Na benzoate (prepd by neutralizing 2g of benzoic acid with 0.6g NaOH). Evaporate the mixt on a w bath to a small vol while the liq still remains clear. Cool and add 50ml of 95% ethanol. This results in a very fine, light yel ppt, which is separated by vacuum filtration. After drying at 50°, analysis gave 41.82% Pb and 3.40% water... 

THAB has been prepared by neutralizing tetrahexylammonium hydroxide, obtained from the iodide by treatment with Ag20, with benzoic acid and evaporation of the water. The analysis of the dried product corresponds to a hemihydrate. The material is somewhat hygroscopic but can be dried by brief heating to 90°C. 

In vain did I endeavor to separate water from the benzoic acid, ° by saturating the crystallized acid with a given quantity of oxide of lead, and therefore could not infer the presence of water of crystallization this analysis farther gave four atoms of oxygen, although I had previously foimd by analysis of the salt of lead that the acid in it saturated three times as much of the oxide as in the neutral benzoate, I was therefore induced since the results did not correspond, to reject this analysis of the crystallized acid. 

FIGURE Al.l Simple separation of four small molecules for calculations of practical use. Separation of mesityl oxide [an EOF (neutral) marker], p-hydroxyphenylacetic acid, p-hydroxybenzoic acid, and benzoic acid [in borate buffer, pH 8.3 3-s pressure ( 0.5 psi) injection]. Analysis was carried out on a Beckman P/ACE System 2050. Separation conditions capillary, 50 /rm x 40 cm (effective length), 47 cm total length bare fused silica T, 28°C voltage, 25 kV buffer, 100 mM borate, pH 8.3 detection, 200 nm. Inset data derived from System Gold (vs7.1) data management software. 

Rosene and Manes studied the effect of pH on the total adsorption from aqueous solutions of sodium benzoate + benzoic acid by activated charcoal. They interpreted their data in terms of the Polanyi potential theory applied to bisolute adsorption (see later p. 117), in which the concentrations of neutral benzoic acid and benzoate anions depend on the pH of the solution (activity coefficient corrections were ignored). They confirmed that, at constant total equilibrium concentration, the adsorption dropped from a relatively high plateau for pH <2 down to a small adsorption at pH >10. The analysis of results is somewhat more complex than with essentially non-electrolyte adsorption, and in this case there were additional effects involving chemisorption of benzoate ion by residual ash in the carbon which had, therefore, to be eliminated. Even with ash-extracted carbon there was evidence of some residual chemisorption. The theoretical analysis correlated satisfactorily with the experimental data on the basis that at pH >10 sodium benzoate is not physically adsorbed and that the effect of pH is completely accounted for by its effect on the concentration of free acid. In addition the theory explains successfully the increase in pH (called by the authors hydrolytic adsorption ) when solutions of sodium benzoate are treated with neutral carbon. However, no account is taken in this paper of the effect of pH on the surface charge of the carbon. 

Fisher and Boles (1990) analyzed the dissolved organic matter in two formation water samples from the San Joaquin Basin by GC-MS analysis of combined acid, base, and neutral methylene chloride extracts. They identified various polar aliphatics (fatty acids to C9 with various methyl and ethyl substituents), cyclics (phenols and benzoic acids), and heterocyclics (quinolines). They were able to quantify, at the ppm or sub-ppm level, phenol, methyl-substituted phenols, and benzoic acid. 

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