670 REPORT — 1887. 



ali-eady iDeen described by II. Schwarz (Ber. XV. ii201), but it will be well to preface 

 our account of the more recent results by a summary of the facts already known, 

 along with such additional points and details as have been found out lately during 

 our investigation. 



a-pyrocrenol, C,-HijO, resembles pure anthracene in appearance, and can be 

 readily obtained in large, shining plates, having a beautiful blue fluorescence or in 

 smaller needles. It is readilj' soluble in benzene, chloroform, carbon tetrachloride, 

 carbon disulphide, less so in acetic acid, alcohol, and ether, and quite insoluble in 

 water and alkalis ; the latter do not act upon it even under pressure. It is like- 

 wise not acted upon by acetyl chloride, phosphorus trichloride, and COCl, solution 

 in benzene — from all of which it can be crystallised without decomposition. It 

 melts at about 196°, solidifying again within 4-6° below that temperature. "\Mien 

 heated more strongly it readily sublimes in beautiful white flakes. It can be 

 volatilised without decomposition, and its vapour density agrees with the formula 

 given above. 



y-liyrocyesol differs from the a-product by its much greater solubility in all 

 solvents, the crystals are less well defined and always needle-shaped. It does not 

 sublime, but can be volatilised without undergoing any change ; the vapour density 

 has also been obtained. Its properties are altogether less marked than those of the 

 a-compound. Melting point 104 to 105°. 



^-pi/rocresol, melting at 124°, stands intermediate between the a- and y- com- 

 pounds in all its properties. 



Oxides of 2>l/rocresol, Cj-IIj.^0.,. 



a-pyrocresol o.vide melts at 168° and forms long, light, yellow needles tui-ning 

 darker" on exposure to the light. It can be distilled, but does not sublime readily. 

 It is much more soluble in acetic acid and alcohol than a-pyrocresol. 



y-pyrocresol oxide melts at 77°, and forms small rhombic plates turning red on 

 exposure to light. 



(3-pijrofresol oxide is less well defined ; its solidifying point lies at 95°. 



The above oxides are obtained by oxidation in acetic acid solution by means of 

 chromic acid. They are indifferent bodies, insoluble in water and alkalis. By 

 gentle reduction with zinc dust, or by III at a moderate heat, they yield the 

 pyrocresols again. "When passed over a loiiir layer of red-hot zinc dust, or 

 heated with a large excess of the strongest III to a high temperature, they are 

 completely decomposed, yielding the same products as the pyrocresols, which will 

 be described below. 



Nitro-compoiuids, Oi-IIg(XO.,)^Oo. 



Kitric acid alone fails to nitrate pyrocresol completely; the product chiefly 

 consists of the oxide. The pure nitro-compounds are therefore obtained by the 

 action of nitrating mixture upon the oxides and recrystallisation from hot acetic 

 acid or nitrobenzene, 



a-tet ranitro-pyrocresol oxide forms small light yellow plates, which on heating 

 burn with a flash. It is sparingly soluble in alcohol and insoluble in caustic 

 potash. 



^-tetraiiitro-pyroa-esol resembles the a-compoimd, but is more soluble in 

 alcohol. 



y-fefra)iifro-pyroc7-esol forms a yellow and granular mass, and is also more 

 soluble in alcohol than the a-derivative. 



By reduction with Xa- amalgam or zinc dust amido compounds have been 

 obtained, but have not yet been prepared in the pure state. 



JIa loffc n-dei ■iva fives. 



When a-pyrocresol is dissolved in cai-Loa tetrachloride, and a stream of chlorine 

 passed through for a long time, the liquid assumes a very pungent smell, different 

 from that of chlorine and strongly reminding of phosgene gas. On standing, this 

 odour disappears, and white granular crystals are gradually deposited. These 

 were recrvstallised from hot benzene and analysed. The numbers obtained showed 



