OF ARTS AND SCIENCES. 67 



techuic acid, alizarine ; with hydrochinone (see Grimm), chinic acid, 

 thiochronic acid, or the a and [3 sulphoacids of hydrochinone, chini- 

 zarine. Still later, in 1875,* they added chlorphenol, boiling-point 

 218°, to the list of substances which form chinizarine, and converted 

 chinizarine into purjrnrine by oxidation. 



In his last paper f on j)htaleines and their derivatives, published in 

 1880, Baeyer shows their close relation to the anthracene group, ordi- 

 nary phtalidiiie deing dioxyphenylaiithranol, while a corresponding 

 compound can be obtained from triphenylmethancarbonic acid. 



8. The syntheses of anthrachinone from benzoylbenzoic acid also 

 begin in 1873, when Phis;cuda and Zincke X obtained a little in oxi- 

 dizing crude bcnzyltoluol. In the following year Behr and Van 

 Dorp § made it by oxidizing tolylphenylketone, and somewhat later in 

 the same year converted (3 benzoylbenzoic acid into anthrachinone || 

 by heating it with phosphoric pentoxide, a process which ran smoothly 

 and yielded 20^ of the theoretical amount, whereas the para-acid, 

 under the same conditions, gave no anthrachinone whatever. The 

 formation of traces of anthrachinone from the distillation of calcic 

 benzoate alone, and of benzoic acid with phosphoric pentoxide, they 

 ascribe to the previous formation of /? benzoylbenzoic acid. Lieber- 

 mann T[ next showed that fuming sulphuric acid produced essentially 

 the same effect as phosphoric pentoxide, converting the (3 benzoyl- 

 benzoic acid into anthracliinone sulphoacid, and suggested that this 

 method misht be of technical value in the future. Rotering and 

 Zincke ** obtained a similar result by using phosphoric pentacliloride, 

 while Thiirner and Zincke ft worked out the process further, and 

 showed that chlorine acting on orthotolylphenylketone produced the 

 same effect. Under this head might also be classed the action of hot 

 plumbic oxide on tolyl[)henylketone already described in Group 2. 



9. Clos'ely related to the preceding group is the synthesis depend- 

 ing on the action of zinc-dust on tolylphenylketone, which was studied 

 by Behr and Van Dorp in 1873 ; $$ also in 1874,§§ when they proved 

 that the para-compound gives no anthracene, and more recently by 

 Ador and Rilliet |||| 



Finally, the occurrence of (10) anthracene among the products of 



* Ber. (1. ch. G., '75, p. 152. ** Ber. d. cli. G., '70, p. 631. 



t Ann. Chem. Pliarm., ccii. 36. tt Ibi<l., '77, p. 1477. 



t Ber. d. ch. G., '73, p. 906. « Ibid., '73, p. 753. 



§ Ibid., '74, p. 16. §§ Ibid., '74, p 16. 



II Ibid., p. 578. nil Ibid., '79, p. 2298. 



TI Ibid., p. 805 



