High alkalinity

High alkalinity is due to the presence of bicarbonates, carbonates and hydroxides of the alkaline earth and alkali metals, principally calcium, magnesium, sodium and potassium. The effect of high alkalinity is to buffer acidity in a soft drink, resulting in the creation of a bland taste, ft is essential therefore to maintain a consistent alkalinity level. The majority of manufacturers aim for below 50 mg/1 as CaC03. Alkalinity may be reduced by coagulation treatment or by ion exchange. 

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As a result of a variable liquid-junction potential, the measured pH may be expected to differ seriously from the determined from cells without a liquid junction in solutions of high acidity or high alkalinity. Merely to affirm the proper functioning of the glass electrode at the extreme ends of the pH scale, two secondary standards are included in Table 8.14. In addition, values for a 0.1 m solution of HCl are given to extend the pH scale up to 275°C [see R. S. Greeley, Anal. Chem. 32 1717 (I960)] ... 

Aqueous solutions of caustic soda aie highly alkaline. Hence caustic soda is ptimatily used in neutralization reactions to form sodium salts (79). Sodium hydroxide reacts with amphotoric metals (Al, Zn, Sn) and their oxides to form complex anions such as AlO, ZnO. SnO ", and (or H2O with oxides). Reaction of AI2O2 with NaOH is the primary step during the extraction of alumina from bauxite (see Aluminum compounds) ... 

Despite the anhydride stmcture, it is remarkably stable, surviving addition to the highly alkaline viscose, the acidic coagulating bath, and also resisting multiple laundering of the rayon fabric. The unusual stability may be attributed to the sulfur atoms, which enhance hydrophobicity, and to the stericaHy hindering neopentyl groups that retard hydrolysis. 

Starch is a polysaccharide found in many plant species. Com and potatoes are two common sources of industrial starch. The composition of starch varies somewhat in terms of the amount of branching of the polymer chains (11). Its principal use as a flocculant is in the Bayer process for extracting aluminum from bauxite ore. The digestion of bauxite in sodium hydroxide solution produces a suspension of finely divided iron minerals and siUcates, called red mud, in a highly alkaline Hquor. Starch is used to settle the red mud so that relatively pure alumina can be produced from the clarified Hquor. It has been largely replaced by acryHc acid and acrylamide-based (11,12) polymers, although a number of plants stiH add some starch in addition to synthetic polymers to reduce the level of residual suspended soHds in the Hquor. Starch [9005-25-8] can be modified with various reagents to produce semisynthetic polymers. The principal one of these is cationic starch, which is used as a retention aid in paper production as a component of a dual system (13,14) or a microparticle system (15). 

Pa.g et s Disease of Bone. Paget s disease, osteitis deformans, occurs mainly ia people over 40. About twice as many men as women are affected. The disease, caused by faulty utilisation of may be mild and asymptomatic requiring Httle or no treatment. Clinical signs are high alkaline phosphatase and high urine hydroxyproline as weU as abnormal bone stmcture which usually goes unrecognised until discovered accidentally by routine x-ray examination (32). 

N,]S7-bis(methoxymethyl)uron was first isolated and described in 1936 (41), but was commercialized only in 1960. It is manufactured (42) by the reaction of 4 mol of formaldehyde with 1 mol of urea at 60°C under highly alkaline conditions to form tetramethylolurea [2787-01-1]. After concentration under reduced pressure to remove water, excess methanol is charged and the reaction continued under acidic conditions at ambient temperatures to close the ring and methylate the hydroxymethyl groups. After filtration to remove the precipitated salts, the methanolic solution is concentrated to recover excess methanol. The product (75—85% pure) is then mixed with a methylated melamine—formaldehyde resin to reduce fabric strength losses in the presence of chlorine, and diluted with water to 50—75% soHds. Uron resins do not find significant use today due to the greater amounts of formaldehyde released from fabric treated with these resins. 

Transportation and Disposal. Only highly alkaline forms of soluble sihcates are regulated by the U.S. Department of Transportation (DOT) as hazardous materials for transportation. When discarded, these ate classified as hazardous waste under the Resource Conservation and Recovery Act (RCRA). Typical members of this class are sodium sihcate solutions having sihca-to-alkah ratios of less than 1.6 and sodium sihcate powders with ratios of less than 1.0. In the recommended treatment and disposal method, the soluble sihcates are neutralized with aqueous acid (6 Af or equivalent), and the resulting sihca gel is disposed of according to local, state, and federal regulations. The neutral hquid, a salt solution, can be flushed iato sewer systems (86). 

High alkalinities of limed juice serve several functions. Foremost is to retard sucrose hydrolysis, one of the oldest reactions in the Uterature of chemical kinetics (6). Sucrose hydrolysis proceeds much more slowly at a moderately high pH than at an even slightly acidic pH. 

High alkalinity, raw water, silica, and CO2 removal required... 

These solutions ate highly alkaline and can effectively remove CO2 or other acidic gases from ambient atmosphere. The octahydrate is also soluble in methanol, but only slightiy soluble in ethanol. 

Another group of chelants that form stable chelates at high pH because of metal—alkoxide coordination are the sugar acids, such as gluconic acid [526-95-4] (1 )- Utility for this group is found in high alkalinity botde washes and other cleansers (19). 

No toxicological hazards have been associated with the normal use of instant color films. However, direct contact with the highly alkaline processing fluids can cause alkafl bums. The fluids are provided in sealed pods and are not usually handled by the user. In the integral systems, the fluids are retained within the film unit and neutralized in the course of processing. In the peel-apart films, residual fluids are rapidly rendered harmless by contact with the air. 

The calcium chelate cements are limited to the use of a cavity liner. They may be placed directly over an exposed tooth pulp to protect the pulp and stimulate the growth of secondary dentin, or used as a therapeutic insulating base under permanent restorations. The high alkalinity and high solubihty of these materials prohibits use in close proximity to soft tissues or in contact with oral fluids. 

Zinc is attacked at high pH. However, in weakly alkaline solutions near room temperature, corrosion is actually very slight, being less than 1 mil/y (0.0254 mm/y) at a pH of 12. The corrosion rate increases rapidly at higher pH, approaching 70 mil/y (1.8 mm/y) at a pH near 14. Just as in aluminum corrosion, protection is due primarily to a stable oxide film that forms spontaneously on exposure to water. High alkalinity dissolves the oxide film, leading to rapid attack. 

Close visual inspection of the blunt, fractured ends revealed small secondary cracks along the internal surface. Internal surfaces were covered with a layer of deposit that was highly alkaline (Fig. 9.18). 

In contrast to thick coatings, thin coatings combined with cathodic protection present certain risks on ships. Blisters filled with highly alkaline liquids resulting... 

Injection of acidic, nutrient-rich water into the highly alkaline soils resulted in "cementing" of the soils. 

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