Acid-base titrations direct aqueous

Since there was no direct reaction of CO with the chloride melt, its concentration in the gas mixture was neglected and corrections for the partial pressure of C02 were not made. The melt was analyzed periodically for this purpose, several samples were taken off the melt, dissolved in water, and subjected to acid-base titration in aqueous solution, to determine the ratio of concentrations of Na20 to Na2C03 as described above. These studies provided the temperature dependences of the equilibrium constant of (1.2.3) in four melts of the KCl-NaCl system in the 1 temperature range 1025 -1125 K, as follows ... 

Direct acid/base titrations in the aqueous phase... 

M-3b Direct Aqueous Alcoholic Acid Base Titrations... 

Fatty acids and acyl sarcosines may be extracted with petroleum or diethyl ether from an acidified aqueous solution if no other surfactants are present, or with petroleum ether from acidified 50% ethanol if they are. The extract is evaporated and the residue weighed. Alkylether carboxylic acids cannot be quantitatively extracted with petroleum ether. They can be extracted from aqueous solution with chloroform, but they are best determined by two-phase titration with benzethonium chloride in akaline solution (bromophenol blue method) or direct potentiometric acid-base titration. 

The second direct method depends on the ability of aqueous potassium chloride, adjusted to pH 4 with carbon dioxide, to selectively elute hydrogen ions from sulfonic acid groups in pulps that first have been converted to their hydrogen form with 0.1 M hydrochloric acid (Cappelen and Schoon 1966). Carbon dioxide is removed from the eluent by sparging with nitrogen and the remaining acid is titrated with 0.1 M sodium hydroxide. Again, a correction factor for interference from carboxylic acids is required. This factor, as before, is based on the protons eluted from bleached pulps by the eluent. As the results depend on the concentration of potassium chloride used, the letter is adjusted so that the sulfonate content corresponds to the sulfur content of pulps assumed to contain only acidic sulfur. 

Carboxylic and sulfonic acid groups import acidity to organic compounds. Most carboxylic acids and sulfuric acids are readily dissolved in water, and their titration with a base is straightforward. If solubility in water is not sufficient, the acid can be dissolved in ethanol and titrated with aqueous base. Aliphatic amines and many saturated cyclic amines can be titrated directly with a solution of a strong acid. Esters are determined by saponification with a measured quantity of standard base. The excess base is titrated with standard acid. 

The first point to be made concerning acids and bases is that so-called acid-base theories are in reality definitions of what an acid or base is they are not theories in the sense of valence bond theory or molecular orbital theory. In a very real sense, we can make an acid be anything we wish the differences between the various acid-base concepts are not concerned with which is right but which is most convenient to use in a particular situation. All of the current definitions of acid-base behavior are compatible with each other. In fact, one of the objects in the following presentation of many different definitions is to emphasize their basic parallelism and hence to direct the students toward a cosmopolitan attitude toward acids and bases which will stand them in good stead in dealing with various chemical situations, whether they be in aqueous solutions of ions, organic reactions, nonaqueotis titrations, or other situations. 

Aliphatic amines generally have base dissociation constants on the order of 10 and can thus be titrated directly with a solution of a strong acid. In contrast, aromatic amines such as aniline and its derivatives are usually too weak for titration in aqueous medium ( Ib 10 °). The same is true for cyclic amines with aromatic character, such as pyridine and its derivatives. Many saturated cyclic amines, such as piperidine, tend to resemble aliphatic amines in their acid/base behavior and thus can be titrated in aqueous media. 

Acid-base potentiometric titration of phenol in aqueous solution is precluded because of its high pATa value (9.98), while 4-nitrophenol (7.41) and 2,4,6-trinitrophenol (0.71) can be directly titrated in that solvent. Nonaqueous titrations of phenol are possible however, difficulties are met when nitrophenols are also present in the system. The determination of carboxylic and phenolic groups in humic acids was carried out by acid-base potentiometric titrations in NaCl solutions up to 1 M. Titration data were processed by linear and nonlinear calculation techniques. ... 

Analytical chemistry has found great utility in conductimetric measurements in spite of its apparent nonspecificity. Rapid quantitative accuracy of a few tenths of a percent may be quickly accomplished by direct conductimetric determination of binary electrolytic solutions such as aqueous acids, bases, or salts. A nearly linear increase in conductivity is observed for solutions containing as much as 20% of solute. The concentration of strong solutions, such as the salinity of seawater, may be determined from conductance measurements traces of electrolyte impurities, such as the impurity in ultrapure water, may be reported at the pgl level. Conductimetric titrations may increase the accuracy of endpoint detection and permit titrimet-ric analysis of weak electrolytes, such as boric acid, which is not feasible by potentiometric or colorimetric... 

We conclude that although titrations of weak bases in non-aqueous superacid solutions often give good estimates of basicity that are directly convertible to the aqueous acidity scale, this method is not always reliable and will be especially dangerous for bases which are themselves good ionizing solvents. 

Chen and Gao studied the use of oscillopolarographic titration, and reported a direct titration of the salts of weak organic bases (or acids) in aqueous solution [61]. In their work, they included the determination of procaine by an oscillopolarographic titration method. 

This technique uses both direct and back titrations of weak acids and bases. Values of are obtained directly. In purely aqueous media, over the pH range 2-10, the titration of dilute (0.005 to 0.05 M) solutions of weak monovalent acids and bases with a glass electrode can lead to reliable thermodynamic pKs. Over this pH interval, the activity coefficients of the ionic species can be calculated by means of the Debye-Hiickel equation. Also, the activity coefficients of the neutral species remain essentially constant and... 

In essence, aqueous titration of surface acidity is an ion-exchange process in which hydrated surface protons are replaced by other hydrated cations (e.g., Na+, NIV") during the course of the titration. The procedure is straightforward. It usually consists of the direct titration of an aqueous suspension of the sample of powdered solid with a dilute base (e.g., sodium hydroxide) to a neutral endpoint. Another commonly used procedure consists of noting the pH of an appropriate salt solution (e.g., ammonium acetate), adding the sample, and measuring the amount of di-... 

A cuprimetric method for the determination of ascorbic acid is based on a direct potentiometric titration with CUSO4 using a copper-based mercury film electrode as the indicator electrode. The electrochemical reaction taking place is ascorbic acid reducing Cu(n) ions quantitatively to Cu(I) ions in neutral or acidic aqueous solutions. The linearity... 

Solution of base B and its perchlorate At the points in a titration between the initial and equivalence points, it is not possible either to reason directly by analogy with titrations in water or to use buffer formulas derived for weak acids in aqueous solutions. The dissociation equilibria of the ion pair BH C104, the acid HCIO4, the base B, and the solvent HOAc all must be considered. 

Where the compounds have extremely low solubility, pKa values may be measured by the solubility method. An aqueous solution of a substance is titrated in the direction of its neutral species tmtil the free base or free acid is precipitated. pfCa can then be calculated from the solubility product. This method is not very accurate but may be used on very dilute solutions. 

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