Peligot tube

OThe gas then passes into two moderately wide wash-bottles each containing 25 c.c. of bromine in order to reduce loss by evaporation the bromine is covered with a layer of water 1 cm. deep and the two bottles are kept cool in a vessel of cold water. If the pressure permits, the last receiver in the train is a Peligot tube (Fig. 48, p. 104)... 

Very pure CuO (15 g.) is dissolved in a clear, carbonate-free solution of 500 g. of NaOH in 330 ml. of HsO (brief refluxing). The dark-blue solution is cooled to 110 C and carefully diluted by adding 140 ml. of H3O through the reflux condenser (use a funnel). The small quantity of unreacted CuO is then filtered off, collecting the filtrate in a preheated Erlenmeyer flask of refined silver. The Erlenmeyer flask is protected by a Peligot tube (filled with 50% KOH) and kept in an electric drying oven for six days at TO C to allow the filtrate to crystallize. The mixture is then filtered the crystals are washed with some 50% and 45% sodium hydroxide (once each) at room temperature and dried on a clay plate over H3SO4. Yield 13 g. 

The oxidation with Brg is more elegant. The flask containing Nas[Fe(OH)4] solution is closed off with a rubber stopper carrying a Peligot tube and a dropping funnel. Then a solution of 2-3 ml. of Brs in 10 ml. of CCU is added dropwise at 50-60 C with vigorous agitation until the iron solution just turns colorless. An excess of Brs must be avoided. The mixture is allowed to stand for two hours at the same temperature and filtered. 

IL Freshly precipitated, thoroughly washed FesOa aq. is added to carbonate-free 50% NaOH. An amount of NaOH equal in weight to the water contained in the FesOa paste is then added and the latter is dissolved with moderate heating (not to exceed 60 °C). The mixture, in a silver Erlenmeyer flask protected with a Peligot tube (filled with 50% KOH), is allowed to stand for several days in an electric drying oven at 70°C. In this manner, the FesOa aq. is completely converted into the nearly colorless, microcrystalline Na4[Fe(OH)7] 2 HsO, which is sparingly soluble in concentrated NaOH. 

Dumas and Peligot (see p. 353) failed to obtain methylene CH and Reg-nault,2 failed to obtain CCP, supposed that methylene does not exist. A. Perrot passed methyl chloride through a red-hot tube but obtained ethylene instead of methylene, and Butlerow obtained ethylene by the action of copper and water on methylene iodide. An attempt by B. Tollens to obtain ethylidene, CHg-CH, by the action of sodium on ethylidene chloride, CHg-CHCla, also gave ethylene. 

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