Freezing baths mixtures

To the deep-red solution is added 550 g. of sodium hydrosulfite (of at least 80 per cent purity) the mixture is stirred for five minutes and then for five 30-second periods during half an hour (Note 5). The solution slowly loses its red color (a thin layer of aniline collects on the surface), and the temperature rises from 25° to 50°. At the end of half an hour the solution should no longer be red it is then rapidly cooled to 20° in a freezing bath and by the addition of about 500 g. of ice. 

Allow the frozen mixture to stand in the freezing bath for another 10 min, then remove the beaker and stand it in tepid water until the frozen plug loosens. 

Polymerization. Freshly distilled 6,8-dioxabicyclo-[3.2.1]octan-7-one and solvent (chloroform, acetonitrile, or 1-nitropropane) were charged into a glass ampule. The ampule was chilled in liquid nitrogen to freeze the mixture, and an initiator solution (usually boron trifluoride ether-ate) was added into the ampule. All these manipulations were carried out under a nitrogen atmosphere. The ampule was evacuated, sealed off and allowed to stand in a constant temperature bath. After the addition of a small amount of pyridine to terminate the polymerization, the reaction mixture, which was in most cases heterogeneous, was dissolved in chloroform, and subjected to gel permeation chromato-... 

A number of the simple ethjdene derivatives may be titrated quantitatively with bromine. The test is, of course, applied only when the previous classification reaction has shown that bromine is decolorized wdthout appreciable substitution taking place. The weighed substance (about 1 g.) is dissolved in 25 cc. of carbon tetrachloride, the mixture cooled in a freezing bath, and titrated with a bromine solution of known sh ength (about N/2) until a faint bromine color remains. 

Into a 1-litre beaker, provided with a mechanical stirrer, place 36 - 8 g. (36 ml.) of aniline, 50 g. of sodium bicarbonate and 350 ml. of water cool to 12-15° by the addition of a little crushed ice. Stir the mixture, and introduce 85 g. of powdered, resublimed iodine in portions of 5-6 g, at intervals of 2-3 minutes so that all the iodine is added during 30 minutes. Continue stirring for 20-30 minutes, by which time the colour of the free iodine in the solution has practically disappeared and the reaction is complete. Filter the crude p-iodoaniline with suction on a Buchner funnel, drain as completely as possible, and dry it in the air. Save the filtrate for the recovery of the iodine (1). Place the crude product in a 750 ml. round-bottomed flask fitted with a reflux double surface condenser add 325 ml. of light petroleum, b.p. 60-80°, and heat in a water bath maintained at 75-80°. Shake the flask frequently and after about 15 minutes, slowly decant the clear hot solution into a beaker set in a freezing mixture of ice and salt, and stir constantly. The p-iodoaniline crystallises almost immediately in almost colourless needles filter and dry the crystals in the air. Return the filtrate to the flask for use in a second extraction as before (2). The yield of p-iodoaniline, m.p. 62-63°, is 60 g. 

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