DERI\AT1V1-:S OF DIPIIENOOUINONE. 255 



able, but when dissolved in carbon tetrachloride at 50" and 

 evaporated in a thin layer in the cold it gave a network of 

 sulphur-yellow needles with straight-extinction. When the 

 same experiment was tried in acetone, the product recovered was 

 unchanged. Conversion was also obtained by dissolving the red 

 variety (m.p. 148) in ethyl acetate at 40°, adding alcohol and 

 then water to turbidity : the very minute pale needles thus 

 obtained melted with decomposition at 161-162°. On the other 

 hand, hot acetone slowly converts the yellow variety into the 

 red, the melting-point changing from 163° to about 140% but 

 the deep-red crystals obtained probably contain some quinhy- 

 drone, as they have a bluish lustre. 



B. DicrcsoquinJiydronc {dicrcsoqniiioiic-dicrcsul ) . C._2^H.2g04, 

 is obtained by adding ferric chloride, not in excess, to a solution 

 of dicresol in much cold dilute alcohol. An interval of half-a- 

 minute elapses before the reaction commences, but in a few 

 minutes the whole of the organic substance is precipitated in 

 very fine microcystalline form, with a brilliant green reflex, so 

 that the suspension resembles alkaline fluorescein. Under the 

 microscope the transmitted colour is a sort of olive brown, and 

 the reflex grass-green. With concentrated sulphuric acid it gives 

 an intense blue coloration {cf. diphenoquinhydrone and coerulig- 

 none). It cannot be recrystallised, though comparatively soluble 

 in alcohol and acetone. Hot alcohol dissociates it completely, 

 dicresoquiinone being left insoluble in orange needles, although 

 dilution with water causes a partial recombination. 0.2815 



N 

 treated with 0.1937 tin in 5% solution used 11.33CC. — I,: H 



= 0.36% for reduction (sample washed out with dilute alcohol 

 and dried over sulphuric acid in vacuo) : C^gH.2f,04 + ^1 requires 

 H = 0.47%. The product is not perfectly white and melts 8° 

 too low for dicresol, but nothing else could be recognised under 

 the microscope. 



Only a poor yield of the quinhydrone is obtainable from 

 dicresol and dicresoquinone in benzene solutions, no reaction 

 occurring for some time, and other amorphous substances being 

 formed. On the other hand, a fairly satisfactory specimen of 

 the quinhydrone is obtained when dicresociuinone is digested 

 with warm bisulphite solution and a trace of alcohol : of this 



N 



0.1003 -\- 0.0935 tin used 5.8 cc. I.^ ; H = 0,41% for reduction. 

 It is still, however, possible that dicresoquinhydrone^ is not a 

 simple addition-product, but our present methods of analysis 

 cannot decide between such closely approximating formulae as 

 C,8 H26 O, and C,, H,o O, for example. 



When covered with a very little .strong caustic soda, a beauti- 

 ful blue-purple sodium salt is obtained, which decomposes on 

 adding water. It could not be obtained by the other methods 

 described by Willstaetter for sodium-diphenoquinhydrone— only 

 mixtures of dicresol and its quinone resulting. 



