T ETRABROMODIPHEN) >-o UINONE. 3 -' 5 



the single benzene-ring (seecoerulignoneand Auwers and Mtarko 

 \ its. Berichte, [905, 226), vis., from 2-(> dibromophenol, failed at 

 first. A small quantity has, however, been obtained as follows: — 

 The starting material is made by distilling tetrabromo-phenol- 

 phthalein with jo^/H^SO.,. It was dissolved in a large quantity 

 of cold water, treated with FeCl 3 , and the mixture nearly neutra- 

 lised with XaHCQ3: it must never become alkaline. Thereon it 

 is slightly warmed and the neutralisation completed by adding 

 KoCrO, until a trace of iron is precipitated, then filtered and 

 kept, at 70-80 for an hour. The precipitate is extracted with 

 excess cold dilute HCl until free from iron, and dried and the 

 soluble bye-products removed by means of ether. The small 

 residue then gives the H a S0 4j and the XaOH reactions for tetra- 

 bromodipheno-quinone. A similar result is given by oxidation 

 in 50% acetic acid with Cr0 3 , the yield being tiny. 



Tetrabromo-diphenoquinone does not dissolve sufficiently 

 for recrystallisation in any solvent : at most 1 part in 2.000 of 

 acetone, benzene or ethylacetate can be dissolved. It dissolves in 

 sulphuric acid to an intense crimson solution, which enables it to 

 be detected in traces. It does not melt, but on heating to 200 

 evolves HBr and chars. All the specimens, even those giving 

 low analyses, when reduced by SnCl2 in presence of alcohol, give 

 tetrabromo-diphenol of considerable purity, melting between 255 ° 

 and 262' C. 



1). Bis-tetrabromo-dipheno quinhydrone: action of caustic 

 alkali on the quinone. — If tetrabromo-diphenoquinone is mois- 

 tened with a little alcohol and covered with excess of caustic 

 alkali, it darkens, and in the course of a few hours is converted 

 into a very beautiful dark blue substance, which is the alkali salt 

 of the above quinhydrone. Heat assists the reaction, but leads to 

 considerable destruction of the product. The product is very 

 slightly soluble in water, and when washed out and air-dried 

 possesses a bright copper lustre. The mother liquor contains 

 tetrabromo-diphenol and what appears to be tribromo- 

 trihydroxy-diphenyl, and, in addition, about 8% of the original 

 bromine as bromide. The blue compound gives a violet coloration 

 to sulphuric acid. In the case of caustic soda, the yield of the 

 blue substance is about 82% of the quinone used. Found Na= 

 4.2 in a specimen dried at no . 



Further work was done with the same substance made 

 directly from tetrabromo-diphenol dissolved in cold caustic soda, 

 by addition of ammonium persulphate and thorough washing out 

 on the Buchner-funnel until the substance began to dissolve. 

 Dried at 120 , (when it lost its lustre, probably from conversion 

 into the free quinhydrone and sodium carbonate by the CO2 of the 

 bath), it gave Na=4.oo, C=2/.io. H=o.97, Br=59.io, which 

 agrees with ( C.H.Br.O.Na, + H L ,0 -f- CO,) or (C^H^B^O, 

 -j- Na,CO.,'. The true formula for the undried substance is, 

 therefore, C vl H K Br H 4 Na, (-j-Aq), being a combination of the 

 quinone with the disodium-derivative of tetrabromo-diphenol in 



