. Practical methods of organic chemistry . a cork bearing a glass tube, not too narrow, bent twice at rightangles. The other end is connected with a flask containing250 of water, by a cork having a small canal in the side(Fig. 70). The tube does not touch theliquid, but the end is about 1 cm. above thesurface. After 50 grammes of benzene and1 gramme of coarse iron filings (the brominecarrier) have been placed in the flask, it iscooled in a large vessel (battery jar) filledwith ice-water; through the vertical tubethere is added 40 = 120 grammes ofbromine : the narrow tube is immediate
. Practical methods of organic chemistry . a cork bearing a glass tube, not too narrow, bent twice at rightangles. The other end is connected with a flask containing250 of water, by a cork having a small canal in the side(Fig. 70). The tube does not touch theliquid, but the end is about 1 cm. above thesurface. After 50 grammes of benzene and1 gramme of coarse iron filings (the brominecarrier) have been placed in the flask, it iscooled in a large vessel (battery jar) filledwith ice-water; through the vertical tubethere is added 40 = 120 grammes ofbromine : the narrow tube is immediatelyconnected with the vertical tube. Aftersome time an extremely energetic reactionwill begin, generally spontaneously, with theevolution of hydrobromic acid, which iscompletely absorbed by the water. Shouldthe reaction not begin at once, the ice-wateris removed for a short time, and if necessarythe flask is immersed for a moment inslightly warm water. But as soon as even aweak gas evolution begins, the flask is at once cooled again, since. AROMATIC SERIES 245 otherwise the reaction easily becomes too violent. Should thishappen in spite of the cooling, the cause is found in the fact thatthe iron filings used were too fine. In other experiments usecoarser filings or small iron nails. When the main reaction isover, the ice-water is removed, the flask dried and heated over asmall flame until the red bromine vapours are no longer visibleabove the dark-coloured liquid. The reaction-product is washedseveral times with water and then distilled with steam. As soonas crystals of dibrombenzene separate out in the condenser, thereceiver is changed and the distillation continued until all the di-brombenzene has passed over. The liquid monobrombenzene isseparated from the water, dried with calcium chloride, and sub-jected to a fractional distillation ; the portion passing over between140-1700 is collected separately. This is again distilled, and theportion going over between 150-1600 collect
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