Addition of acid or alkali

Addition of alkali has the opposite effect, and at about pH 11 almost all the soluble calcium phosphate occurs in the colloidal phase. These changes are not reversible on subsequent dialysis against untreated milk. 

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Pontevedrine (369) is a red compound from Papaveraceae (71TL3093). The UV-VIS absorption maxima Imax in ethanol were found at 245 (4.59), 312 (4.28), 325 (4.39), and 470 (4.01) nm. On addition of acid or alkali no changes were observable. A zwitterionic structure was proposed on the basis of the NMR data (Scheme 110). 

The pH can be adjusted by the addition of acid or alkali. Lime is frequently used to neutralise acidic effluents. 

It must be emphasized that the equilibrium pH must be the same in all tests. One way of ensuring this is to check the pH of the aqueous phase after equilibration of the phases, adjust if necessary by the addition of acid or alkali, and then mix the phases again till equilibrium is reached. 

For hydrogen production from water, pure water (pH=7.0) is seldom used as an electrolyte. Water is a poor ionic conductor and hence it presents a high Ohmic overpotential. For the water splitting reaction to proceed at a realistically acceptable cell voltage the conductivity of the water is necessarily increased by the addition of acids or alkalis. Aqueous acidic and alkaline media offer high ionic (hydrogen and hydroxyl) concentrations and mobilities and therefore possess low electrical resistance. Basic electrolytes are generally preferred since corrosion problems are severe with acidic electrolytes. Based on the type of electrolytes used electrolyzers are... 

The chemical composition of the cooling water makeup supply used in the plant determines the choice of the cycles of concentration. Some of the important constituents that must be controlled in the tower are calcium, magnesium, silica, carbonate, bicarbonate and sulfate ions. Alkalinity levels are regulated by the addition of acid or alkali to achieve the desired pH. When adding H2S04 (sulfuric acid) for pH control, it should be assured that calcium sulfate solubility limits are not exceeded (see Chapter 8). 

Buffer solution - one which resists a change in H. onccniration (pH) on i addition of acid or alkali. 

In aqueous solution, riboflavin has absorption at ca 220—225, 226, 371, 444 and 475 nm. Neutral aqueous solutions of riboflavin have a greenish yellow color and an intense yellowish green fluorescence with a maximum at ca 530 nm and a quantum yield of = 0.25 at pH 2.6 (10). Fluorescence disappears upon the addition of acid or alkali. The fluorescence is used in quantitative determinations. The optical activity of riboflavin in neutral and acid solutions is [a]=-H56.5-59.5 (0.5%, dilHCl). In an alkaline solution, it depends upon the concentration, eg, [a] =—112-122 (50 mg in 2 mL 0.1 iV alcohoHc NaOH diluted to 10 mL with water). Borate-containing solutions are strongly dextrorotatory, because borate complexes with the ribitji side chain of riboflavin [ct] ° = +340° (pH 12). 

Water is a major constituent of all living organisms, and the seas support millions of different species of plant and animal life. Yet the pH values of both water and saline (salt) solutions are particularly sensitive to the addition of acids or alkalis. Look ... 

The pH can be adjusted by the addition of acid or alkali. Lime (calcium oxide) is frequently used to neutralize acidic effluents. In the case of sulfuric acid, the use of lime leads to formation of calcium sulfate. Calcium sulfate that is potentially contaminated with trace organic material has low value and can be used as road fill. An alternative approach is to neutralize with more expensive ammonia, forming ammonium sulfate, which can be sold as a fertilizer. 

Chemically a buffer solution is defined as one that resists a change in pH on addition of acid or alkali. Buffer solutions contain compoimds that react with both acid or base so that the H+ ion concentration in the solution remains constant. The buffer solutions thus have reserve acidity or reserve alkalinity . Buffer solutions usually consist of a mixtures of solutions of a weak acid or base and its salt, for example, acetic acid and sodium acetate. The pH of the buffer is governed by salt-acid ratio and the ionisation constant of the acid and is given by Henderson... 

Most activation processes leave the carbon with an alkaline reaction although a few produce an acid carbon. The pH can be adjusted by supplementary addition of acid or alkali to meet the varied needs of different industrial users.61 When the intended use requires a low soluble-ash content, the carbon is washed with water, or with acid and then with water.62 ... 

The specific rotation of an aqueous solution of pilosine falls when the solution is allowed to stand, and it is profoundly altered by the addition of acid or alkali data regarding the optical activity of the alkaloid and its degradation products are included in Table 6. (See also Table 9.)... 

In order to compensate for partial decomposition of water because of overcharge and corrosion, water must be regularly added. Normally addition of acid or alkali solutions is inadmissible as the resulting increase in electrolyte concentration impairs battery characteristics. Only deionized water (if unavoidable, pure rainwater or melted snow may be acceptable) is to be added to the electrolyte. This water must not be kept in metal containers as even very small amounts of iron ions (or ions of other metals) introduced into the electrolyte are very harmful to batteries. Chloride ions present in normal tap water are also very dangerous. It should be kept in mind that boiling of water does not remove either chloride or iron ions. When water is added, the electrolyte must come to the level indicated in the manual for each specific battery (usually it is 3-5 mm above the upper edges of the plates). A certain time is required for the concentration to level off in the bulk of the electrolyte. 

During the test period, the flow through each section of lead piping is checked three times a week, at the same time that test water pH is checked and when a small sample of the test water leaving the lead pipe section is taken for lead analysis. At these times, pH adjustments are made if necessary using small additions of acid or alkali. At the end of the test period, the test water is allowed to stagnate for 16 hours within the lead pipe section, prior to a further sample being obtained for lead analysis. 

The relatively flat portions of titration curves are where the pH changes most slowly on addition of acid or alkali. These flat portions are, therefore, where the best buffering action occurs. They are known as the buffer regions. 

Another useful property of a buffer, at least within the range pH 4 to 10, is that its pH remains substantially unchanged upon dilution of the solution. The effectiveness of a buffer depends on its buffer capacity (resistance to pH change on addition of acid or alkali), the pH change on dilution, and the effects of adding neutral salts or changing the temperature. These are discussed in Chapter 2. 

This variation in buffering power with pH is illustrated in Figure 1.2. The pK of the buffer pair in the buffer solution was 7.0 units. For pH values in the range 6.0 to 8.0, addition of acid or alkali produces much smaller changes in pH in the buffer solution than in water. Beyond this range, both solutions show similar changes in pH as more and more acid or alkali is added. 

Reaction In acid-base physiology, reaction is similar in meaning to pH . The reaction of a solution means the pH of a solution . An anion whose concentration is reaction-dependent is one whose concentration changes with addition of acid or alkali, e.g. bicarbonate. 

The chemiosmotic theory requires that a proton gradient artificially created across the membrane by addition of acid or alkali to the external medium should lead to the synthesis of ATP. This last prediction has been verified by a sudden... 

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