409-21-2 carborundum

The formation of silicon carbide, SiC (carborundum), is prevented by the addition of a little iron as much of the silicon is added to steel to increase its resistance to attack by acids, the presence of a trace of iron does not matter. (Addition of silicon to bronze is found to increase both the strength and the hardness of the bronze.) Silicon is also manufactured by the reaction between silicon tetrachloride and zinc at 1300 K and by the reduction of trichlorosilane with hydrogen. 

Larger fragments of porcelain would absorb appreciable quantities of the sodium hydroxide, which would be only slowiy extracted by the acid during the subsequent titration hence finely dh ided carborundum may well be used (P. 8). 

The action of this and other anti-bumping devices e.g., minute carborundum chips) is dependent upon the fact that the transformation of a superheated liquid into the vapour will take place immediately if a vapour phase e.g., any inert gas) is introduced. The effect may be compared with that produced by the introduction of a small quantity of a solid phaM into a supercooled liquid, e.g., of ice into supercooled water. 

Pulverized ferrosilicon containing approximately 15 percent sihcon is available from the Foote Mineral Company and from Carborundum Co. in the sizes and at the prices shown in Table 19-14. Cost is based on truckload quantities in 227-kg (500-lb) steel drums, FOB Keokuk, Iowa, and Niagara Falls, Ontario. 

The first commercial polymer Table 21.3, II) was offered in 1965 by Union Carbide as Bakelite Polysulfone, now renamed Udel. In 1967 Minnesota Mining and Manufacturing introduced Astrel 360 Table 21.3, V), which they referred to as a polyarylsulfone. In 1972 ICI brought a third material onto the market which they called a polyethersulphone (III) and which they then marketed as Victrex. They also introduced a material intermediate between III and V known as Polyethersulphone 720P (IV) but which has now been withdrawn. In the late 1970s Union Carbide introduced Radel (VI), which has a higher level of toughness. Around 1986 Union Carbide sold their interest in polysulphones to Amoco. In addition the Astrel materials were produced by Carborundum under licence from ICI. 

The PE fibres are produced by melt spinning a novolak resin of molecular weight ca 1000 and then cross-linking the molecules by exposure to gaseous formaldehyde at 100-150°C for 6-8 h or with a formaldehyde solution. The fibres were introduced under the tradename Kynol by American Kynol Inc., a subsidiary of Carborundum AG. 

In the 1960s the Carborundum company introduced the polymer Ekonol P-3000. This was the polymer of p-hydroxybenzoic acid (I) Figure 25.22), in practice produced by the self-ester exchange of its phenyl ester to prevent decarboxylation. A blend with PTFE, Ekonol T-4000, was also produced. 

Bromine (128 g., 0.80 mole) is added dropwise to the well-stirred mixture over a period of 40 minutes (Note 4). After all the bromine has been added, the molten mixture is stirred at 80-85° on a steam bath for 1 hour, or until it solidifies if that happens first (Note 5). The complex is added in portions to a well-stirred mixture of 1.3 1. of cracked ice and 100 ml. of concentrated hydrochloric acid in a 2-1. beaker (Note 6). Part of the cold aqueous layer is added to the reaction flask to decompose whatever part of the reaction mixture remains there, and the resulting mixture is added to the beaker. The dark oil that settles out is extracted from the mixture with four 150-ml. portions of ether. The extracts are combined, washed consecutively with 100 ml. of water and 100 ml. of 5% aqueous sodium bicarbonate solution, dried with anhydrous sodium sulfate, and transferred to a short-necked distillation flask. The ether is removed by distillation at atmospheric pressure, and crude 3-bromo-acetophenone is stripped from a few grams of heavy dark residue by distillation at reduced pressure. The colorless distillate is carefully fractionated in a column 20 cm. long and 1.5 cm. in diameter that is filled with Carborundum or Heli-Pak filling. 4 hc combined middle fractions of constant refractive index are taken as 3-l)romoaccto])lu iu)nc weight, 94 -100 g. (70-75%) l).p. 75 76°/0.5 mm. tif 1.57,38 1.5742 m.]). 7 8° (Notes 7 and 8). 

An applicator stick (available from drug stores) can be used very conveniently to ensure smooth boiling. If a boiling chip is used, it should be colored (Carborundum, for example) to make its separation from the product convenient. 

Parameter P is equal to the ratio of the liquid volume entrained and the sum of the volumes of this liquid and particles. Values of P are determined experimentally from measured settling velocities. In general, the smaller the effective particle size, the more liquid is entrained by the same mass of solids phase. For example, particles of carborundum with d = 12.2 //.m have P = 0.268 d = 9.6 ftm, p — 0.288 and d = 4.6 fim, p = 0.35. 

Silicon carbide was made accidently by E. G. Acheson in 1891 he recognized its abrasive power and coined the name carborundum from carbo(n) and (co)rundum (AI2O3) to indicate that its hardness on the Mohs scale (9.5) was intermediate between that of diamond (10) and AI2O3 (9). Within months he had formed the Carborundum Co. for its manufacture, and current world production approaches 1 million tonnes annually. 

Reactions under pressure are usually carried out in an autoclave. However, several simple vessels can be used for reactions at moderate pressure. A heavy walled Pyrex test tube or Kjeldahl flask drawn out and sealed with an oxygen torch makes a suitable container for many Diels-Alder reactions. The tube can be heated in an oil or water bath, but care must be exercised to protect against explosions. At the conclusion of the reaction, the tube is cooled to room temperature, the neck is scratched with a file or carborundum chip, and a hot Pyrex rod is touched to the scratch. A large crack in the neck should result, and the sealed top can be easily knocked off. 

Solvent-free high-build floor paints are available which can be readily applied with brush, roller or spray to a prepared concrete substrate to give a thickness of 0.10-0.20 mm per coat. Normally, two coats are applied and the first is often lightly dressed with fine sand or carborundum dust to give a non-slip, chemically resistant and durable colored floor, ideal for light industrial traffic conditions (for example, rubber-shod wheels). ... 

Kuhn, W. E., More Zirconium Facts, I No. 2, Carborundum Metals Company, 4 (1957)... 

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