Showing papers on "Aluminium hydroxide published in 1971"

Conditions for the Formation of Bayerite and Gibbsite

Abstract: Aluminium hydroxide gels have been prepared by the hydrolysis of amalgamated aluminium in water and by precipitation from aluminium salt solutions with an anion exchange resin in the hydroxyl form. The products crystallizing from such gels have been examined by electron microscopy and by X-ray and electron diffraction. Bayerite crystallizes as cone or pyramid-shaped particles and gibbsite as hexagonal plates or prisms. Two types of gel are postulated. The first type, pseudoboehmite, predominates in the absence of acids, is uncharged and rapidly crystallizes to bayerite; the second type, pregibbsite gel, occurs in carboxylic acid solutions, is positively charged and, in the absence of inorganic anions, crystallizes slowly to gibbsite.

Constitution and properties of silica-alumina-catalysts

Abstract: Since Eugene Houdry discovered some clays to be excellent catalysts for the “cracking” of heavy oils, the surface properties of silica-alumina combinations have been studied in various places and from various angles. The surface properties of silica-alumina-combinations differ in many ways from those of silica or of alumina, as such. Three different procedures for preparing the silica-aluminas may be mentioned, viz., (a) adsorption (chemisorption) of aluminium hydroxide on a wet silica surface, (b) precipitation of aluminium hydroxide on a wet silica gel, (c) co-gelling of a silica acid-and an aluminium salt solution. The influence of the alumina adsorption on the specific surface area, as measured with the B.E.T.-method and with the lauric acid method will be discussed. An attempt is made to give a picture of the binding of aluminium hydroxide on the silica, which leads to three possibilities, depending on the relative amount of both constituents. One of these possibilities leads to preparations with an acid character.

481. 海水中のウランの採取,(i)

Abstract: With the view to studying the possibility of separating uranium from sea-water by coprecipitation, the carrier properties of ferric, aluminium and titanium hydroxides were examined, with the following results:(1) The values of pH at which uranium started to coprecipitate with the carriers were 4.5 for ferric hydroxide, 5.0 for aluminium hydroxide and 2.8 for titanium hydroxide.(2) Optimum pH values for decarbonated sea-water to obtain maximum recovery of uranium were 8-9 for aluminium and ferric hydroxides, and 4.5-9 for titanium hydroxide with natural sea-water, the values were appreciably lower for ferric and aluminium hydroxides, but unchonged for titanium hydroxide.(3) In the case of ferric and aluminium hydroxides, the coprecipitation ratios of uranium were much smaller in natural than in decarbonated sea-water. With titanium hydroxide however, uranium coprecipitated with equal ease in natural sea-water as in decarbonated sea-water.(4) Uranium was effectively separated from the carri rs by carbonate salt extraction but not by acid extraction.

Recombination of atoms at surfaces. Part 11.—Nitrogen atoms at some acid, base and salt surfaces

Abstract: The Rayleigh method has been used to investigate the effect on the recombination of nitrogen atoms of treating Pyrex with materials such as H3PO4, NaOH, NaCl, Al(OH)3 etc. The significance of some of these in relation to the mechanism of the process occurring at a Pyrex surface has been discussed. Phosphoric and sulphuric acids lower the activity and the process becomes second order. Aluminium hydroxide increases the activity considerably.

A process for two-layer enamelling by a single stoving

Abstract: 1,236,614. Two layer enamelling by a single stoving. FARBENFABRIKEN BAYER A.G. 17 June, 1968 [7 July, 1967], No. 28655/68. Heading C1M. In a two-layer enamelling process by a single stoving a primer enamel slip is applied to the object, e.g. a metal such as sheet steel, to be enamelled and dried, a surface enamel is then applied and the two layers are stoved, generally at a temperature of 720‹ to 820‹ C. The primer enamel slip, which may be sprayed on to the object as a finely ground suspension in a very thin layer, comprises a finely divided primer enamel frit and 1 to 4% by weight of at least one aluminate and 2 to 15% by weight of at least one phosphate. Suitable phosphates are the ortho-, poly-, and metaphosphates of Li, Na, K, Mg, Ca, Sr, Ba, Zn, Al, Fe, Co and/or Ni and suitable aluminates include alkali metal aluminates, aluminium hydroxide, aluminium oxide hydrates and gamma Al 2 O 3 . Adhesion of the primer may be improved by adding to the slip metal oxides or hydroxides. The surface enamel may be white, coloured or transparent. In the examples the primer enamel frit has the following compositions in per cent by weight:-SiO 2 : 39A5, 42; Al 2 O 3 : 5, 6; B 2 O 3 : 19, 17; Na 2 O: 19, 19; K 2 O: 4, 4; F: 2, 2; CaO: 6, 6; NiO: 3, 3; CoO: 1A5, 1: P 2 O 5 : 1, 0. The slips are free of conventional mill additives such as quartz or clay or have a much lower content of these additives.