576 CONSIDERATION OF CARBON COMPOUNDS. 



iodine in potassium iodide upon an alkaline solution of thymol. Condensation 

 of two molecules of thymol takes place with the introduction of two atoms of 

 iodine into its phenolic group. It is a bright, chocolate-colored, or reddish- 

 yellow, bulky powder, with a very slight aromatic odor; it contains 46.14 per 

 cent, of iodine and is used as a substitute for iodoform. 



Resorcinol, C G H 4 (OH) 2 . 1:3 = 1O9.22 (Resorcin 9 Meta-dihydroxy- 

 benzene). It is formed by fusing different resins, such as galbanum, 

 asafoetida, etc., with caustic alkalies, but it is now made almost alto- 

 gether from benzene by heating the latter with fuming sulphuric acid 

 to 257 C., whereby benzene-meta-disulphonic acid, C 6 H 4 (SO 3 H) 2 , 

 is produced. The sodium salt of this acid is fused with sodium 

 hydroxide for several hours, forming sodium resorcin, C 6 H 4 (ONa) 2 . 

 The mass is dissolved in water, acidified, and extracted with ether, 

 which dissolves out the resorcin. This is further purified by sub- 

 limation and recrystallization. 



Resorcinol is a white, or faintly-reddish, crystalline powder, having a some- 

 what sweetish taste and a slightly aromatic odor; it fuses at 119 C. (246 F.), 

 boils at 276 C. (529 F.), and is soluble in less than its own weight of water. 

 A dilute solution gives with ferrric chloride a bluish-violet color. Resorcinol, 

 when heated for a few minutes with phthalic acid in a test-tube, forms a yel- 

 lowish-red mass, which, when added to a dilute solution of caustic soda, forms 

 a highly fluorescent solution. Other fluorescent compounds are obtained by 

 heating resorcinol with very little sulphuric and either citric, oxalic, or tar- 

 taric acid, dissolving in a mixture of water and alcohol and supersaturating 

 the solution with ammonia. Resorcinol is largely used in the manufacture of 

 certain dyes. It must not be confused with the proprietary preparation of the 

 same name, composed of equal parts of resorcin and iodoform fused together. 



Quinol, C 6 H 4 (OH) 2 .1 : 4 (Hydroquinone, Para-dihydrozy-benzene), is formed 

 by dry distillation of quinic acid (from Peruvian bark), by reduction of 

 quinone, and by fusing para-iodophenol with sodium hydroxide. It occurs 

 combined with sugar as the glucoside arbutin, in uva ursi (Bear-berry) leaves. 

 It forms small plates or hexagonal prisms, melting at 169 C., easily soluble in 

 hot water, alcohol, and ether. Oxidizing agents, such as ferric chloride, chlo- 

 rine, etc., convert it into quinone, C 6 H 4 O 2 . It is used as a developer in pho- 

 tography. 



Solution of lead acetate gives a white precipitate with pyrocatechol, none 

 with resorcinol, and a precipitate only in the presence of ammonia with 

 hydroquinol. 



Pyrogallol, Pyrogallic acid, C 6 H 3 .(OH) 3 . When gallic acid is 

 heated to 200 C. (392 F.) it is decomposed into carbon dioxide and 

 pyrogallol, a substance which is not a true acid, but a tri-hydroxy- 

 benzene i. e., a phenol. Pyrogallol crystallizes in colorless needles, 

 melts at 131 C. (268 F.), is easy soluble in water, ether, and alco- 

 hol. In alkaline solution it absorbs oxygen rapidly, assuming a red, 



