Carborundum chips

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. 

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. 

Carbon dioxide, 184, 358, 359 solid see Dry Ice Carbon disulphide, 767 purification of, 175 Carbon monoxide, 185, 1003, 1004 Carbon, decolourising, 127, 128 Carbon tetrachloride, 733, 815 drying of, 734 purification of, 176 Carbonyl chloride, 185 Carborundum chips, 4 Carboxylic acids, equivalent weights of, 1071 ... 

Where a recrystallisation has been conducted in a centrifuge or small diameter tube and too much solvent has been added initially, concentration of the solution may be effected by the following technique. A small carborundum chip is introduced and the tube is heated very carefully over a water or oil bath of suitable temperature to give gentle boiling. A flow of nitrogen is directed to the surface of the boiling liquid by means of a capillary-end pipette the process is continued until the required concentration is effected. The technique of concentration may also be used in those cases where further crystalline crops are required from the mother-liquor. 

Scratching of tube of this size is accomplished by a carborundum glass cutter, which is easily constructed by fusing a carborundum chip in the end of a glass rod. Alternatively a diamond pencil may be used. 

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. 

A 500-ml. flask is charged with 318 g. (3 moles) of 1,2,4-tri-hydroxybutane (Note 1) and 3 g. of -toluenesulfonic add monohydrate. A few Carborundum boiling chips are added, the flask is equipped with a 30.5-cm. Vigreux column, condenser, and receiver arranged for vacuum distillation, and the contents are heated, with swirling, to dissolve the acid (Note 2). The flask is then heated in a bath held at 180-220° so that 300-306 g. of distillate, b.p. 85-87°/22 mm., is collected over a period of 2-2.5 hours (Note 3). The colorless liquid obtained is refractionated, the same apparatus being used, and two fractions are collected the first, 50-60 g., b.p. 42-44°/24 mm., wff 1.3343, is mainly water. After a negligible intermediate fraction, 215-231 g. (81-88%) of pure 3-hydroxytetrahydrofuran, b.p. 93-95°/26 mm., tin 1.4497, df1 = 1.095, is collected (Note 4). 

Should the base of a graduated cylinder be chipped, the sharp edges are ground off on the side of the carborundum cutting wheel. No other repairs should be attempted, as the base is usually of very thick glass and will not survive heating. 

Large billets of the rare earth metals with the exception of Eu can be cut on an oil-cooled power hack saw or water-cooled carborundum cut-off wheel. Since the reactivity of these metals increases with temperature, any method chosen should have a means of keeping the metal cool. Intermediate size billets can be cut with a hack saw, but must be kept cool to prevent contamination especially by hydrogen which is formed by reaction of the metal with H2O. The metal chips from sawing the light lanthanides, especially Ce and La, wilTreadily ignite and... 

Two common types of boiling stones are carborundum and marble chips. Carborundum boiling stones are more inert, and the pieces are usually small, suitable for most applications. If available, carborundum boiling stones are preferred for most purposes. Marble chips may dissolve in strong acid solutions, and the pieces are larger. The advantage of marble chips is that they are cheaper. 

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