Aluminium paste, compound

The fluxes used when brazing are alkali halide and borate mixtures and compounds, and they have two main functions first, to dissolve the oxide film on the component surface or at least to degrade its adhesion by penetration of naturally occurring flaws and electrolytic action at the oxide-substrate interface, and secondly to prevent formation on the liquid surface of oxide skins which would restrict braze flow. Fluxes can be contained in a bath held at the brazing temperature in which the, usually aluminium, component is placed or else applied as a paste to surfaces of the component or braze. 

This is a complex salt of sucrose sulphate and aluminium hydroxide. In the acid environment of the stomach, the aluminium moiety is released so that the compound develops a strong negative charge and binds to positively charged protein molecules that transude from damaged mucosa. The result is a viscous paste that adheres selectively... 

Alloys of antimony and aluminium look very much like silver and have been used in the past in forging our coins. One such florin analysed by the author in 1911 contained aluminium 53 40, and antimony 46 38 per cent with traces of lead, arsenic and iron. With copper a violet alloy, probably a compound SbCuj, is formed known as regulus of Venus. Small amounts of antimony are used in stiffening lead. Antimony oxide is used, associated with titanium oxide, as a white pigment, as for example in titanox. 

An example of the use of a fire retardant additive is antimony trioxide. A paste of this and certain chlorinated organic compounds can be made compatible with all normal resins and be easily dispersed by simple mechanical mixing. When 20% of the basic resin is replaced by such a paste, laminates with low surface spread-of-flame can be produced. Smaller percentages will give less fire resistance. Another paste dispersion, of antimony trioxide, may be used in a resin based on HET acid but can only be mixed with certain ordinary resins. Other fire retardant additives include aluminium trihydrate (ATH). 

Cyclic Disulphides and Cyclic Diselenides.—Formation. No fundamentally new methods of synthesis of this class of compounds have been reported in the past two years. For l,2>dithiolan the oxidation of l,3>dithiols remains a favoured method, the use of iodine in the presence of triethylamine leading smoothly to 1,2-dithiolans without attendant polymerization. cis- and tra/ -l,2-Dithiolan-3,5-dicarboxylic acids were prepared from a diastereo-isomeric mixture of dimethyl 2,4-dibromoglutarates by sequential treatment with potassium thioacetate and potassium hydroxide in the presence of iodine,and jyn-2,3-dithiabicyclo[3,2,l]octan-8-ol was formed from 2,6-dibromocyclohexanone by successive treatment with potassium thiocyanate, lithium aluminium hydride, and iodine. The stereoselective formation of the less thermodynamically stable alcohol in this case was attributed partly to the formation of chelates with sulphur-aluminium bonds. 2,2-Dimethyl-l,3-dibromopropane was converted into 4,4-dimethyl-l,2-diselenolan on treatment with potassium selenocyanate at 175 °C, but at 140 °C the product was 3,3-dimethylselenetan. Reductive debenzylation of 2-alkylamino-l,3-bis(benzylthio)propanes with lithium in liquid ammonia and oxidation of the resultant dithiols with air afforded 4-dialkylamino-l,2-dithiolans, whilst treatment of a-bromomethyl-chalcone with sodium hydrosulphide gave, as minor product, trans-3 phenyl-4-benzoyl-l,2-dithiolan. Among the many products of thermal decomposition of /ra/ -2,4-diphenylthietan was l,4,5,7-tetraphenyl-2,3-dithiabicyclo [2,2,2]octane. ... 

Compound Paste of Aluminium, B.P.C. Contains 40 per cent of zinc oxide and 20 per cent of powdered aluminium in a paraffin base. 

Titanium catalysts were soon abandoned as they produced elastomers with poor elasticity. However, they have recently been reconsidered and elasticity values have been obtained which are comparable with the best elastomers obtained with vanadium compounds." Coupling a vanadium compound with an aluminium compound obviously opens the way to many combinations and past research has been pointed towards the most suitable one. It is in fact on catalyst choice that process efficiency and quality of the finished product depend. 

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