Alkali attack

Fused alkalis attack glass if several preparations are to bo carried out, a copper flask should be used. 

Tantalum is a gray, heavy, and very hard metal. When pure, it is ductile and can be drawn into fine wire, which is used as a filament for evaporating metals such as aluminum. Tantalum is almost completely immune to chemical attack at temperatures below ISOoC, and is attacked only by hydrofluoric acid, acidic solutions containing the fluoride ion, and free sulfur trioxide. Alkalis attack it only slowly. At high temperatures, tantalum becomes much more reactive. The element has a melting point exceeded only by tungsten and rhenium. Tantalum is used to make a variety... 

The metals react with most non-metals especially if heated, but resist alkali attack and are less reactive towards acids than might be expected. Concentrated HCl probably reacts most rapidly, but even here insoluble residues remain in the cases of Th (black). Pa (white) and U (black). Those of Th and U have the approximate compositions HThO(OH) and UH(OH)2. Concentrated HNO3 passivates Th, U and Pu, but the addition of F ions avoids this and provides the best general method for dissolving these metals. 

Diaziridines are stable toward alkalies. Aciueous alkali attacks pentamethylenediaziridine on heating not more quickly than does pure water. Further investigation has not yet been undertaken. However, reductive fission and hydrolytic fission in acid media have been studied in detail. 

Grayish-white cubic crystals lustrous and brittle density 5.323 g/cm hardness 6.0 Mohs melts at 938.2°C vaporizes at 2,833°C a poor conductor of electricity electrical resistivity 47 microhm-cm dielectric constant 15.7 specific magnetic susceptibility (at 20°C) 0.122x10 insoluble in water, dilute acids and dilute alkalies attacked by concentrated nitric and sulfuric acids, aqua regia and fused alkalies. 

Forsterite Refractories. Refractories made from forsterite, Mg2Si04, resist alkali attack and have good volume stability, high temperature strength, and fair resistance to basic slags. Uses include nonferrous metal furnace roofs and glass-tank refractories not in contact with the melt, ie, checkers, ports, and uptakes. 

In the later paper(Ref 6), Ashford et al described amylose nitrate with N=13.25%. Hot alkali attacked it slightly more than amylopectin nitrate... 

The vapours of the alkali metals are without action even at 2000° C.2 Boiling solutions of the alkalis attack tantalum slowly fusion with caustic potash in air yields a tantalate. 

Elimination of chromite that makes the brick less susceptible to alkali attack in service... 

Based on the analyses of the trace contaminants conducted on the wheat millfeed-derived products, numerous potential problem components were identified, relative to catalyst activity (3). These components (shown in Table 1) include sulfate (potential for metal sulfide formation) calcium, magnesium, and phosphate (potential for catalyst pore plugging by insoluble salt precipitation) sodium or potassium (alkali attack on the catalyst support) organic nitrogen components, such as amino acids (thiol... 

Effect of strong alkalis Attacked Slight Decomposes... 

PROP A bright, white, soft, ductile metal sltly radioactive. Corrosion resistant (oxide film). Resistant to fused alkalies, attacked by hot concentrated mineral acids. Bp 3380°, d 6.11 18.7°, mp 1917°. Insol in water. CONSENSUS REPORTS Reported in EPA TSCA Inventory. 

When GeCl4 is passed with an inert carrier gas through a tube at 1000° and then over a cold surface, brown (GeCl) separates (Schwarz and Baro-netzky, 1954). The substance is insoluble in most solvents. Alkalis attack it ... 

To determine the mechanisms of alkali attack and resulting reaction products, laboratory-prepared powders of alkali and alumino-silicate refractories have been fired at various temperatures. Results obtained from these reaction tests have supported the findings from the field samples. Alkali slag tests are performed by the various manufacturers to determine how their products withstand corrosion by alkalies. 

Farris and Allen [27] used two techniques to study the effect of alkali on various refractories. One, a reactive test, concerned the alkali attack on refractories in the range of 42% to 90% alumina content. Specifically, a superduty and bricks of 60%, 70%, 70% high fired, and 90% alumina were ground and mixed with alkali and fired to temperatures from 1575 to 2625°F. The resulting reactions products were identified by x-ray diffraction techniques (XRD). 

Semi-silica compositions The NazO-95% Si02/5% A1203 vertical section (Fig. 9) shows that as Na20 reacts with a semi-silicate refractory, all Si02 phases should disappear, and tridymite, the only stable form of silica, will form very slowly. Albite will form only at temperatures below 1050°C and liquid is present down to 740°C. Semi-silica refractories are not resistant to alkali attack, and may be even less alkali-resistant than high-silica refractories. 

Properties Excellent hardness, gloss, flexibility, abrasion resistance, and adhesion resistant to impact, weathering, acids, and alkalies attacked by aromatic and chlorinated solvents. Applied by brash, spray, or dipping. Combustible. 

The pH values on the surface of normal skin vary between 4.5 and 6, and up to a certain point the skin has the ability to defend itself against pH variations and can maintain a stable pH in the face of moderate acid or alkali attacks. This is the skin s buffer capacity (Box 6.1). 

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