Sulfates, aluminium

Aluminium fluoride (anhydrous) [7784-18-4] M 84.0, m 250°. Technical material may contain up to 15% alumina, with minor impurities such as aluminium sulfate, cryolite, silica and iron oxide. Reagent grade AIF3 (hydrated) contains only traces of impurities but its water content is very variable (may be up to 40%). It can be dried by calcining at 600-800° in a stream of dry air (some hydrolysis occurs), followed by vacuum distn at low pressure in a graphite system, heated to approximately 925° (condenser at 900°) [Henry and Dreisbach J Am Chem Soc 81 5274 1959]. 

For preparing lakes, a solution of aluminium sulfate (or chloride) is mixed with sodium carbonate, forming fresh alumina Al(OH)3. The colorant is then added and adsorbed on the surface of alumina. Usually the content of colorant in the lake ranges from 10 to 40%." The product is filtered, washed with water, dried, and milled. The product is allowed to contain unreacted alumina but must not contain more than 0.5% HCl-insoluble matter and not more than 0.2 % ether-extractable matter. - Lakes are insoluble in most solvents used for pure dyes, and they have high opacity and better stability to light and heat. Lakes impart their color by dispersion of solid particles in the food. The coloring properties of lakes depend on particles, crystal structures, concentrations of dye, etc. 

The production of a baking powder depended on a system where the reaction could be delayed until required. In 1864 a patent was taken out to use monocalcium phosphate hydrate in making a baking powder. In 1885 sodium aluminium sulfate came to be used. This compound has a low solubility in water at ambient temperatures so it does not start to act until the product has heated up. 

Sodium aluminium sulfate SAIP NaH14Al3(P04)8 4H20 + 5H2Q - 3Al(OH)3+Na+ + 4H2PO[Pg.74]

The total amounts of hydroxide ions, calculated by summing moles of 0H added (as NaOH, Pr NOH, sodium aluminate or sodium silicate) and by substracting moles of acid added (as H2SO4 or aluminium sulfate), are 16.45, 19.3 and 8.8 for mixtures A, B and B respectively. Their final ingredient molar ratios are compared in Table I. 

For the period from around 1840 to the early 1970s paper was usually made in an acidic environment at pHs of around 4-5. This was because many grades required the use of rosin and aluminium sulfate for the control of water penetration (sizing), and solutions of aluminium sulfate exhibit a pH of around 4.5. Aluminium sulfate has also been popular with paper makers because it assists the flocculation of colloidal particles and therefore behaves as a mildly... 

Sizing chemistry is critically linked to the pH of the paper-making system, and the oldest and most established sizing system involves the use of wood resin acids and aluminium sulfate. The presence of aluminium sulfate gives rise to an acidic pH ( 4.5), because the aluminium ion in aqueous solution exists as a hexahydrated complex capable of dissociation according to the equilibria shown in equations 7.1-7.3. Further equilibria are also possible. 

Furuno, T., Uehara, T. and Jodai, S. (1991). Combinations of wood and silicate I. Impregnation by water glass and applications of aluminium sulfate and calcium chloride as reactants. Mokuzai Gakkaishi, 37(5), 462 72. 

Aluminium sulfate Unknown s s Calcium hypochlorite Solution s s... 

Aluminium sulfate Unknown s Calcium chloride Unknown S... 

Aluminium sulfate Unknown S Chlorosulfonic acid Unknown n... 

Aluminium sulfate Unknown S Iron(III) chloride Unknown s... 

Aluminium sulfate Unknown S Dilute bases Unknown 1... 

Okaya Y,s. Ahmed M. S., Pepinsky R. Vani> V. X-ray crystallographic study of room temperature modification of monomethyl aluminium sulfate alum. Z. Cryst. 1957 109 367. 

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