DER[VATIVKS OF DIPHENOOUINONE. 259 



The nearl}- black crystalline product is filtered ofif at once and 

 ^vashed with acetic acid and a little alcohol. It forms black 

 needles or flat hexagons with a lustre like that of graphite, melt- 

 ing with decomposition at 165-170° according to the rate of 

 heating. 



0.222^ gave 0.2281 Aglh- — Hr = 43.6%. 



N 

 0.0905 used 0.9OCC y SnClg against a blank — H for reduction 



= 0.20%. 



C28H2204Br4 requires Br =: 43.1, H = 0.27%. 



As prepared by the action of ferric salts on the dilute 

 alcoholic solution of dibromodicresol, it is obtained in fine divi- 

 sion, showing a chocolate-brown transmission colour and an 

 intense blue-green lustre. 



It is also obtainable by adding a little bromine to an acetic 

 acid solution of dil^romodicresol at 60° : black tabular crystals 

 with green lustre ; the mother liquor contains the quinone and 

 ]iossibly the perbromide described by the author.* For analysis 

 it was ground in an agate mortar and boiled with standard 

 stannous chloride and an excess of acetone till colourless : 0.1447 

 used 0.0267 tin : H for reduction = 0.31% : on diluting, the 

 \vhole of the reduction-product was obtained in crystalline form,, 

 melting at 182-4°, therefore practically pure dibromodicresol. 



On boiling the qiiinhydrone with alcohol or acetone, it is 

 gradually completely dissociated and the quinone crystallises 

 out : on diluting the orange mother-liquor, the quinhydrone is,, 

 however, partly re-formed. 



Tetrabromo-dicresoquinhydrone gives a fine blue coloration 

 wuth sulphuric acid, which developes a red edging on standing. 

 Its alkali salts can be obtained by rubbing it up with a trace of 

 verv strong alkali, but is decomposed by water : bright blue 

 gelatinous substance, with brilliant coppery lustre : it was not 

 obtained on treating disodium-dibromodicresol with io'dine or 

 ferricyanide — onlv mixtures of the quinone and the unoxidised 

 substance resulted. 



On oxidising an acetic solution of a mixture of monobromo- 

 and dibromodicresol (the product of a bromination of dicresot 

 where, owing to too low temperature and " protection," the action 

 was incomplete ; /;/./'. 161-3°), tribroiiioificrcsoquiiihydroiic was 

 obtained: black graphitic needles : found 34.6 and 35.7% Br,, 

 and H for reduction = 0.25%. 



C28 H23 O4 Brg requires Br = 36.2, H = 0.30. 



On boiling with acetone, the corresponding quinone or mix- 

 ture of quinones was left : red microscopic needles, apparently 

 uniform; Found Br = 35-i%- 



Trans. 1907, 1311. 



