310 PYROGALLOL. 



c. Veratrol is produced by heating veratric acid 

 with an excess of baryta. Colorless oil, of an aromatic 

 odor; boils at 202-205, and congeals in crystalline 

 format +15. 



^.^Thymohydroquinone, C 10 H 14 2 = C 10 H 12 (OH) 2 . Is 

 obtained from thymoquinone by treating with sul- 

 phurous acid. Clear, four-sided prisms, of a vitreous 

 lustre. Fusing point, 139.5 Sublimes without de- 

 composition. Difficultly soluble in cold water, easily 

 in boiling water. Oxidizing substances convert it 

 easily into thymoquinone. 



d. Triatomic Phenols. 



Pyrogallol (Pyrogallic Acid). 

 C 6 H 6 3 = C 6 H 3 (OH) 3 . 



Formation. By heating gallic acid alone, most ad- 

 vantageously in an atmosphere of carbonic anhydride, 

 at 210-220, or with two to three times its weight of 

 water, in a closed vessel, at 200-210. In smaller 

 quantity by heating gallotannic acid. 



Properties. Shiny, colorless laminae or needles of a 

 bitter taste. Poisonous. Sublimable without decom- 

 position when the air is not allowed to have access. 

 Easily soluble in water. In the presence of alkalies it 

 takes up oxygen rapidly from the air, and decomposes, 

 yielding carbonic anhydride, acetic acid, and brown, 

 amorphous substances. It gives a blackish-blue color 

 with iron sulphate, a red color with iron chloride. It 

 reduces the metals rapidly from gold, silver, and mer- 

 cury salts. 



Triacetylpyrogallol, C 6 H 3 (O.C 2 H 3 0) 3 , is produced 

 by dissolving pyrogallol in an excess of acetyl chloride, 

 and remains behind on evaporation in small, sublimable 

 crystals, insoluble in water. 



Tribrompyrogallol, C 6 Br 3 (OH) 3 , is produced "by 

 mixing pyrogallol with bromine. Shiny, flat, rhombic 



