TETRABR) IM0-DIP1 1 ENO-QU 1 NON E. 2> 2 7 



analysis K=i4«4, Br=44.i. The same substance is apparently 

 obtained by nitrating the crude tribromo-diphenol of page 323. 

 Found in K-salt, K=i5.o. Br=4i.o. It is probably impure 3' 

 nitro-3-5-5-' tribromo-diphenol. Owing to the low solubility of 

 the starting material — tetrabromodiphenol — nine of these sub- 

 stances can be conveniently prepared in quantity. 



II. Action of neutral sulphite on tetrabromodiphenoquinone. 

 — This is similar, except that nearly twice as much bromin : is 

 split off. From the mother-liquor, after removing tetrabromo- 

 diphenol, I isolated a quantity of potassium dibromo-diphenol- 

 disulphonate (already described in Trans. Chan. Soc, Louden, 

 igoj. 1308), giving- a brilliant blue colouration with FeC.13. Found 

 K=i2. 53. S=n. 50. Theory : K = 13 4, S—ll.l. On nitration 

 this gives t,~?>' dinitro-5-5' dibromo-diphenol of m.p. 237 . 

 Another salt is present, much more soluble, and giving an olive 

 colour with FeCl3. This is probably the result of replacing part 

 of the bromine in tetrabromo-diphenol by hydroxyl, so as to give 

 an adjacent dihydroxy-derivative, which explains the colour. 



Again, on using silver bisulphite for reduction, a -imilar 

 substance, but containing the sulphonic group, was obtained. Its 

 potassium -alt also formed white needle-, and gives the olive 

 coloration with FeCl3. Found K=8.6, Br=33.8 

 HO SO.,K 



HO~< >—■ >OH 



requires K=8.2, Br=33.5. 



I. The substance described by the author in 1906 as " true 

 tetrabromo-diphenoquinone " made by Willstaetter's method 

 (PbO a in dry benzene), has never been obtained in sufficient 



quantity to investigate. The only analysis made gave 60.1 % Br, 

 which is nearly 4% too low for tetrabromo-diphenoquinone. 

 The white product obtained by reducing it with SnCL melted 

 at 245-8 , and was mainly tetrabromo-diphenol. The 

 original substance is probably tetrabromo-diphenoquinone, accom- 

 panied or combined with dibromo-quinone ; and the name "true 

 tetrabromo-diphenoquinone " should be withdrawn. 



J. Preparation of 2-G dibr ino-quinoue. — 2-6 dibromo-sidph- 

 anilic aeid was first made by treating solution of potassium stil- 

 phanilate with a mixture of bromate and bromide, and acidifying 

 until some tribromaniline separates ; the filtered liquor was 

 neutralised with ammonia and concentrated. This gives a much 

 better yield than the methods in the literature. The potassium 

 salt forms rather sparingly soluble needles, and gives a blood-red 

 coloration with FeCl3. When dissolved in warm dilute sulphuric 

 acid and treated with CVO3 in excess, it is converted into the 

 dibromo-quinone, which separates as a brown oil, rapidly solidi- 

 fying: recrystallised from benzene with addition of alcohol, 



