Sodium—continued press

In a 500 ml. bolt-head flask, provided with a mechanical stirrer, place 70 ml. of oleum (20 per cent. SO3) and heat it in an oil bath to 70°. By means of a separatory funnel, supported so that the stem is just above the surface of the acid, introduce 41 g. (34 ml.) of nitrobenzene slowly and at such a rate that the temperature of the well-stirred mixture does not rise above 100-105°. When all the nitrobenzene has been introduced, continue the heating at 110-115° for 30 minutes. Remove a test portion and add it to the excess of water. If the odour of nitrobenzene is still apparent, add a further 10 ml. of fuming sulphuric acid, and heat at 110-115° for 15 minutes the reaction mixture should then be free from nitrobenzene. Allow the mixture to cool and pour it with good mechanical stirring on to 200 g. of finely-crushed ice contained in a beaker. AU the nitrobenzenesulphonic acid passes into solution if a little sulphone is present, remove this by filtration. Stir the solution mechanically and add 70 g. of sodium chloride in small portions the sodium salt of m-nitro-benzenesulphonic acid separates as a pasty mass. Continue the stirring for about 30 minutes, allow to stand overnight, filter and press the cake well. The latter will retain sufficient acid to render unnecessary the addition of acid in the subsequent reduction with iron. Spread upon filter paper to dry partially. 

The solid is suspended in 300 ml. of 5% sodium hydroxide at 15° (Note 5). The mixture is stirred for 30 minutes, and the solid is filtered by suction and washed with water until the filtrates are no longer alkaline. The procedure is repeated, but stirring is continued for 0.75-1.0 hour. After the solid has been filtered by suction, washed, and pressed as dry as possible, it is dried under reduced pressure over phosphorus pentoxide for 12-16 hours. 

The equations are sometimes useful, but it must be borne in mind that the formulae are equations of continuous curves, whereas actual solubility curves are not usually continuous except over limited ranges of temp, determined by the stability of particular phases—e.g. hydrates. The effect of pressure on the solubility of sodium chloride has been previously indicated. C. Moller showed in 1862 that the solubility is increased by 20 and by 40 atm. press. The thermal expansion of salt soln. was also found by G. C. Schmidt to be more regular than with water. W. C. Rontgen and J. Schneider, and V. Schumann, have measured the compressibility of soln. of potassium and sodium chlorides. 

Fifty grams of pure cobalt carbonate are prepared by slowly adding a saturated solution of the equivalent quantity of the chloride, nitrate, or sulfate to a hot solution of 60g of anhydrous sodium carbonate in 600ml of water. Some effervescence takes place The mixture is digested at the boiling point with continual stirring for at least 16 minutes and then suction-filtered, washed freely with hot water, and pressed as dry as possible mi the filter. Alternatively, 51g of technical cobalt carbonate may be dissolved in the minimum amount of 63f hydrochloric add (about 140ml), filtered, and reprecipitated as described ... 

In a 3-I. beaker are placed no g. (1.2 moles) of aniline, 150 g. (1.76 moles) of sodium bicarbonate and 1 1. of water, and the mixture is cooled to 12-15° by the addition of a small amount of ice. The beaker is then fitted with ail efficient mechanical stirrer. The blade of a large porcelain spatula should be inserted into the liquid to overcome the rotary motion and thus obtain better mixing. The stirrer is started and 254 g. (1 mole) of powdered iodine is added in 15-20 g. portions at intervals of two to three minutes so that all the iodine is introduced during the course of one-half hour. Stirring is continued for twenty to thirty minutes. By this time the reaction is complete, and the color of the free iodine in the solution has practically disappeared. The crude -iodoaniline, which separates as a dark crystalline mass, is collected on a Biichner funnel, pressed as free from water as possible, and dried in the air. The filtrate may be saved for the recovery of iodine (Note 1). 

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