Alkalinity definition

Because the initial alkalinity is 0, the change in alkalinity is simply the final value (AAt = At). Using these relations and the alkalinity definition we can write ... 

The equation contains two unknowns Pc02 and nH+. The alkalinity definition can be used to get PCO2 n terms of At and ith+. The resulting equation is ... 

In the beginning, there were only general explanations for the acidic taste phenomenon for instance, indicators can show the acid manner by its color. Later, there were explanations of acidic-alkaline definitions based on the structure of the material - they were, however, always based on acidic or alkaline solutions as chemical substances. Today, the most common definition for beginners is the Broensted Lowery concept and the idea of a proton transfer from one particle to another particle. Flowever, this definition is based more on the function of ions or molecules as acid particles - and not on acids as substances The different historic acid-base concepts are briefly described in the following periods of time ... 

Many other organic acids important in water chemistry have p/Cg values similar to that of acetic acid, for example, propionic acid and butyric acid. Many natural waters contain silicates and organic bases that contribute to the total alkalinity. Wastewaters contain substantial quantities of organic bases, ammonia, and phosphates. Anaerobic digester supernatant often contains high concentrations of bases similar to acetate, as well as carbonates, ammonia, and phosphates. For very complex systems for which a detailed chemical analysis is not available, no attempt is made to work with the mathematical definition of alkalinity. However, if the system is chemically defined we can show that these substances will contribute to alkalinity if, during the titration, some of the base is converted to the conjugate acid. We can modify the total alkalinity definition to include these species so that... 

The residual liquid in the flask is a dilute alkaline solution of sodium acetate. To liberate the acetic acid, add dilute sulphuric acid until the solution is definitely acid to litmus, and then distil off about 20 ml. Perform on this aqueous distillate the tests for acetic acid given on p. 347-... 

Suspend the crude hydrochloride in some water in a separating-funnel and add 20% sodium hydroxide solution until the mixture is definitely alkaline and the crude phenylhydrazine base floats as a deep red oil on the surface. Now extract the phenylhydrazine twice with benzene (using about 30 ml. of benzene on each occasion) and dry the united benzene extracts with powdered... 

Next cool the alkaline residue in the flask and add dil. H2SO4 until definitely acid. 

Hemicellulose [9034-32-6] is the least utilized component of the biomass triad comprising cellulose (qv), lignin (qv), and hemiceUulose. The term was origiaated by Schulze (1) and is used here to distinguish the nonceUulosic polysaccharides of plant cell walls from those that are not part of the wall stmcture. Confusion arises because other hemicellulose definitions based on solvent extraction are often used in the Hterature (2—4). The term polyose is used in Europe to describe these nonceUulosic polysaccharides from wood, whereas hemicellulose is used to describe the alkaline extracts from commercial pulps (4). The quantity of hemicellulose in different sources varies considerably as shown in Table 1. 

The alkalinity is determined by titration of the sample with a standard acid (sulfuric or hydrochloric) to a definite pH. If the initial sample pH is >8.3, the titration curve has two inflection points reflecting the conversion of carbonate ion to bicarbonate ion and finally to carbonic acid (H2CO2). A sample with an initial pH <8.3 only exhibits one inflection point corresponding to conversion of bicarbonate to carbonic acid. Since most natural-water alkalinity is governed by the carbonate—bicarbonate ion equiUbria, the alkalinity titration is often used to estimate their concentrations. 

Two other methods worth discussing are wet air oxidation and regeneration by steam. Wet oxidation may be defined as a process in which a substance in aqueous solution or suspension is oxidized by oxygen transferred from a gas phase in intimate contact with the liquid phase. The substance may be organic or inorganic in nature. In this broad definition, both the well known oxidation of ferrous salts to ferric salts by exposure of a solution to air at room temperature and the adsorption of oxygen by alkaline pyrogallol in the classical Orsat gas analysis would be considered wet oxidations. 

Taft began the LFER attack on steric effects as part of his separation of electronic and steric effects in aliphatic compounds, which is discussed in Section 7.3. For our present purposes we abstract from that treatment the portion relevant to aromatic substrates. Hammett p values for alkaline ester hydrolysis are in the range +2.2 to +2.8, whereas for acid ester hydrolysis p is close to zero (see Table 7-2). Taft, therefore, concluded that electronic effects of substituents are much greater in the alkaline than in the acid series and. in fact, that they are negligible in the acid series. This left the steric effect alone controlling relative reactivity in the acid series. A steric substituent constant was defined [by analogy with the definition of cr in Eq. (7-22)] by Eq. (7-43), where k is the rate constant for acid-catalyzed hydrolysis of an orr/to-substituted benzoate ester and k is the corresponding rate constant for the on/to-methyl ester note that CH3, not H, is the reference substituent. ... 

C,4H2204, melting at 182 5. The formation of this cedrene-dicarboxylic acid serves for the detection of cedrene in essential oils. It is sufficient if the fraction to be examined be oxidised by permanganate or ozone, and the acid obtained (boiling-point at 10 mm. = 200° to 220° C.) be then oxidised further, either by an alkaline solution of bromine or by nitric acid. Even very small proportions of cedrene have definitely led to the obtaining of this acid melting at 182 5° C. 

No simple osmium aqua ion has been definitely isolated and characterized, though in alkaline solution (and the solid state) the osmium(VIII) species 0s04(0H)2 is well characterized (sections 1.4.1 and 1.12.1). 

Humic substances in sediments and soils have commonly been, defined as heteropolycondensates of decomposing plant and animal detritus 46. For lack of a better structural definition, these macromolecular substances have been divided into three categories fulvic acids and humic acid and humin. Fulvic acids and humic acids are soluble in dilute alkaline solutions, whereas humin is insoluble. 

It can be seen that these definitions are derived from experimental observation and are no more than classifications based on a set of properties shared by a group of substances. They are scientifically inadequate for the interpretation of results, which requires a definition based on concepts. Historically, the attempt to provide a model rather than a classification comes in the form of a search for imderlying universal principles. It seems that the alchemists recognized vague principles of acidity and alkalinity, and in the 17th century the iatrochemists made these the basis of chemical medicine. Disease was attributed to a predominance of one or other of these principles (Pattison Muir, 1883). 

A formal definition of salt hydrolysis can follow from the description outlined above. Salt hydrolysis may be defined as a reaction in which the anion or the cation of a salt reacts with the solvent water to produce acidity or alkalinity. Evidently, it is the nature of the anion or the cation constituting the salt which will determine whether the solution produced as a result of hydrolysis will be acidic or alkaline. If the matter is examined from these points of view, the following three different cases can arise. 

Acidic wastes with a pH of <2.0 and alkaline wastes with a pH of >12.5 are defined as hazardous (40 CFR Part 261). To meet the regulatory definition of nonhazardous, acidic wastes must be neutralized to a pH of >2.0 by reducing the hydrogen ion concentration, and alkaline wastes must be neutralized to a pH of <12.5 by increasing the hydrogen ion concentration. 

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