BENZENE SERIES. AROMATIC COMPOUNDS. 381 



which differ in their physical properties and in their physiological 

 action. The uaphtol which is used medicinally is chiefly beta-naphtol, 

 a solid compound crystallizing in thin, shining plates, having an odor 

 similar to phenol and a burning, acrid taste. It fuses at 122 C. 

 (252 F.), boils at 286 C. (547 F.), is insoluble in about 1000 parts 

 of cold or 75 parts of boiling water ; and readily soluble in alcohol, 

 ether, chloroform, and fatty oils. The aqueous solution is colored 

 green by ferric chloride. Naphtol is found in coal-tar, but is usually 

 prepared from naphtalin. 



Santonin, C 15 H 18 O 3 . Although many efforts have been made to 

 disclose the constitution of santonin, and though many derivatives of 

 it have been formed, we know as yet but little of its structure, but 

 it may be the anhydride of santonic acid, C 15 H 20 O 4 . As several re- 

 actions point to a relationship between santonin and naphtalin, it is 

 mentioned in this place. 



Santonin is the active principle of wormseed, the unexpanded 

 flowerheads of Artemisia, from which it is obtained by extraction 

 with alcohol and lime-water, and decomposition of the soluble com- 

 pound of lime and santonin by an acid. Santonin crystallizes in 

 colorless prisms, which turn yellow on exposure to light ; it is but 

 sparingly soluble in water, more soluble in alcohol and ether. 



Santonin taken internally confers upon the urine a dark color re- 

 sembling the color of urine containing bile ; upon heating such urine 

 it turns cherry-red or crimson, the color disappearing on the addition 

 of an acid, and reappearing on neutralization. 



Analytical reactions : 



1. Santonin added to alcoholic solution of potassium hydroxide 

 produces a bright-red liquid which gradually becomes colorless. 

 (Plate VI., 5.) 



2. To 1 c.c. of sulphuric acid add a few drops of ferric chloride 

 solution and a crystal of santonin : on heating, a dark-red color is 

 produced, changing into violet-brown. 



QUESTIONS. 471. What is the difference between fatty and aromatic com- 

 pounds, and from which two hydrocarbons are they derived ? 472. From what 

 source is benzene obtained, how can it be made from benzoic acid, and what 

 are its properties? 473. Give the graphic formulas of benzene, nitro-benzene, 

 cymene, phenol, thymol, benzoic acid, and salicylic acid. Mention methane 

 derivatives which have a constitution analogous to that of the substances 

 mentioned. 474. Give composition, properties, and mode of manufacture of, 



