BENZENE SERIES. AROMATIC COMPOUNDS. 375 



camphor has the composition C 10 H 18 O, while the camphor found 

 in the camphor-trees of China and Japan has the composition 

 C 10 H 16 0. 



Camphor, Camphora, C 10 H 16 O (Laurinol), forms white, translucent 

 masses of a tough consistence and a crystalline structure ; it has a 

 characteristic, penetrating odor and poisonous properties; in the 

 presence of a little alcohol or ether it may be pulverized ; it is nearly 

 insoluble in water, but soluble in alcohol, ether, chloroform, etc. ; 

 boiled with bromine it forms the monobromated camphor, C 10 H 15 BrO, 

 of the U. S. P., a white crystalline substance having a mild cam- 

 phoraceous odor and taste. Heating with nitric acid converts cam- 

 phor into camphoric acid, C 8 H 14 (CO 2 H) 2 , a colorless, crystalline, 

 fusible substance, having an acid taste ; it is slightly soluble in water, 

 readily in alcohol and ether. 



Menthol, C 10 H 19 OH (Mint-camphor}. Found together with a 

 terpene in oil of peppermint, and separates in crystals on cooling the 

 oil. Menthol is nearly insoluble in water, fuses at 43 C. (109 F.) 

 and boils at 212 C. (414 F.). It has the characteristic odor of 

 peppermint. 



Thymol, C 10 H 14 O or C 6 H 3 .CH 3 .C 3 H 7 .OH (Methyl-propylphenol). 

 Thymol is found in small quantities as a constituent of the volatile 

 oils of wild thyme, horse-mint, and a few other plants. 



Thymol crystallizes in large translucent plates, has a mild odor, a warm, 

 pungent taste, melts at 50 C. (122 F.) and boils at 230 C. (446 F.) It is now 

 largely used as an excellent and very valuable antiseptic, preference being 

 given to it on account of its comparative harmlessness when compared with 

 the strongly poisonous carbolic acid. 



Thymol dissolved in moderately concentrated warm solution of potassium 

 hydroxide, gives on the addition of a few drops of chloroform a violet color, 

 which on heating soon changes into a beautiful violet-red. 



Eucalyptol, C 10 H 18 0, is found in the volatile oils of different species of 

 eucalyptus, as also in the oils of some other plants. It is liquid at the ordinary 

 temperature, but solidifies when cooled to a little below the freezing-point. It 

 has an aromatic, distinctly camphoraceous odor. 



Benzole acid, Acidum benzoicum, HC 7 H 5 O 2 or C 6 H 5 CO 2 H = 

 122. Found in benzoin and some other resins ; also in combination 

 with other substances in the urine of herbivorous animals; it is 

 obtained from benzoin by heating it carefully, when the volatile 

 benzoic acid sublimes. It is now also manufactured from toluene, 



