Neutralizing value

Tlie amphoteric behavior of aluminum hydroxide, wliich dissolves readily in strong acids and bases, is shown in Figure 4. In the pH range of 4 to 9, a small change in pH towards the neutral value causes rapid and voluminous precipitation of colloidal hydroxide wliich readily fomis a gel. Gels are also fomied by the hydrolysis of organoaluminum compounds such as aluminum alkoxides (see Alkoxides, metal). 

Common name [Chemical Abstracts name] CAS Registry Number Formula Neutralizing value Uses ... 

The neutralizing value (NV) of leavening acid detemiines the number of parts by weight of baking soda that will be neutralized by 100 parts of the acid to impart neutral pH in baked goods. 

Because the ionic product of water = [H ] [OH ] = 1.04 x 10" at 25°C, it follows that pH = 14 - pOH. Thus, a neutral solution (e.g., pure water at 25°C) in which [H j = [OH ] has a pH = pOH = 7. Acids show a lower pH and bases a higher pH than this neutral value of 7. The hydrogen ion concentrations can cover a wide range, from -1 g-ion/liter or more in acidic solutions to -lO" " g-ion/liter or less in alkaline solutions [53, p. 545]. Buffer action refers to the property of a solution in resisting change of pH upon addition of an acid or a base. Buffer solutions usually consist of a mixture of a weak acid and its salt (conjugate base) or of a weak base and its salt (conjugate acid). 

We saw in Section J that a salt is produced by the neutralization of an acid by a base. However, if we measure the pH of a solution of a salt, we do not in general find the neutral value (pH = 7). For instance, if we neutralize 0.3 M CHjCOOH(aq) with 0.3 M NaOH(aq), the resulting solution of sodium acetate has pH = 9.0. How can this be The Bronsted-Lowry theory provides the explanation. According to this theory, an ion may be an acid or a base. The acetate ion, for instance, is a base, and the ammonium ion is an acid. The pH of a solution of a salt depends on the relative acidity and basicity of its ions. 

In what follows, unless specified otherwise the breaking and joining parameters, Pb and J, will be assigned the neutral values Pb = TO and J = 1.0 appropriate to hard-sphere (billiard ball) collisions. In some cases it will be of interest to depart from this simple model and to alter these values to find the influences of intermolecular attractions and repulsions on the results. 

The figures presented in Table 1 were confirmed by other reactions giving identical results, as will be shown later. It seems very improbable that the ratio of 1 2 3 4 of the neutralization values occurred by chance. The simple ratio implies that four different groups of characteristic acidities occur side by side in equivalent amounts. Very likely, they are part of a bigger complex. 

In this case, too, complete oxidation was essential for finding the simple ratio of the neutralization values of 2 3 4 5. Completion of the oxidation was recognized by the appearance of brown colloidal solutions when the samples were washed with alkali. The colloids were removed by washing first with alkali, then with dilute hydrochloric acid and water, before any further experiments were done. 

In a Friedel-Crafts reaction, the chloride was treated with dimethyl-aniline in the presence of aluminum chloride. Nitrobenzene was used as solvent. After exhaustive extraction, the nitrogen content was equimolar to the former chloride content. No NaHCOj was neutralized by the reaction product the other neutralization values decreased correspondingly. 

Information concerning the position of the carboxyl groups relative to each other was obtained from the neutralization behavior after reaction with thionyl chloride 35, 47). More base ought to be consumed by such products because additional alkali is used for the neutralization of the hydrochloric acid liberated on hydrolysis. As is shown in Table VII, the additional alkali consumption was equivalent to the quantity of chloride ions found in the solution. However with all the samples which had been activated with carbon dioxide, less sodium ethoxide was consumed than had been expected. The deficit was equivalent to half the NaHCOj neutralization value. This strange behavior can be explained only by... 

After treatment with ammonia gas and outgassing at 20° an NHj uptake equivalent to the NajCOa neutralization value was observed repeatedly 35). 

The neutralization values were influenced by reduction with strong reducing agents, lithium aluminum hydride, sodium borohydride, and amalgamated zinc plus hydrochloric acid (35, 46). For the most part, the consumption of NajCOj and of NaOEt decreased in equivalent amounts. This is further confirmation of the assumption that lactones of the fluorescein type or of the lactol type are present. The reaction with sodium ethoxide was shown to be no true neutralization, that is, exchange of H+for Na+, at all, but an addition reaction w ith the formation of the sodium salt of a semi-acetal or ketal ... 

The neutralization behavior was different from that of oxidized microcrystalline carbon. No relationship was observed between the neutralization values with different bases as is found in Tables I and III for black microcrystalline carbon. Samples outgassed at -800° adsorbed no alkali. 

Procedure (neutralizing value). At the same time as weighing the sample for moisture determination, weigh 0.5 g (AOAC 1 g, but 0.5 g for CaO or Ca(OH)2), or x g, of the prepared sample to the nearest 0.001 g, and transfer to a 300-ml (AOAC 250-ml) conical flask. Add 50 ml of 0.5 M hydrochloric acid, cover the flask with a watch glass and boil the contents gently for 5 min. Cool the mixture to room temperature, add 2 or 3 drops of the phenolphthalein indicator and titrate with 0.5 M sodium hydroxide solution to the end point of the indicator. 

The neutralizing value is expressed as a percentage by weight of calcium oxide (CaO) and refers to the undried sample as received. Thus the formula becomes ... 

Upon s.c. injection, the insulin experiences an increase in pH towards more neutral values and, consequently, appears to precipitate in the subcutaneous tissue. It resolubilizes very slowly and hence a greatly prolonged duration of release into the bloodstream is noted. Consequently, a single daily injection supports the maintenance of acceptable basal blood insulin levels, and insulin molecules are still detected at the site of injection more than 24 h after administration. 

Part of the North Branch of the Potomac River runs crystal clear through the scenic Appalachian Mountains, but it is lifeless—a victim of acid drainage from abandoned coal mines. As the river passes a paper mill and a wastewater treatment plant near Westemport, Maryland, the pH rises from an acidic, lethal value of 4.5 to a neutral value of 7.2, at which fish and plants thrive. This happy "accident comes about because calcium carbonate exiting the paper mill equilibrates with massive quantities of carbon dioxide from bacterial respiration at the sewage treatment plant. The resulting soluble bicarbonate neutralizes the acidic river and restores life downstream of the plant.1... 

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