BENZENE SERIES. AROMATIC COMPOUNDS. 589 



duce no color, but if alplia-naphthol is present, an intensely violet 

 color is produced. 



Naphthol occurs in coal-tar, but it is prepared synthetically from 

 naphthalene in the same manner in which phenol is prepared from 

 benzene. When concentrated sulphuric acid is heated with naphthalene 

 for several hours at 200 C., the beta-sulphonic acid is formed, C 10 H 7 - 

 SO 3 H ; during the early stage of the process, and particularly at 80- 

 90 C., much alpha-sulphonic acid is formed, but at a higher temper- 

 ature this is converted into the beta variety. The sodium salt of the 

 beta acid is fused with sodium hydroxide, forming sodium naphthol 

 and sodium sulphite. By treating the former with an acid, beta-naph- 

 thol is liberated, which must be further purified. 



Microeidine, C 10 H 7 .ONa, is the name given to sodium naphthol. 

 ItS aqueous solution is used as a disinfectant for cleansing dental 

 instruments. 



Alpha-naphthol is obtained in the same manner as the beta product, from 

 the sodium salt of alpha-naphthalene sulphonic acid. It forms lustrous needles, 

 melting at 95 C. and boiling at 278-280 C. It is more readily soluble in water 

 than beta-naphthol, and is said by one author to be three times more powerful 

 as an antiseptic and only one-third as poisonous as the beta compound. It is 

 official in the French Pharmacopoaia. Most authorities state, however, that it is 

 more poisonous than beta-naphthol. It has been used as a test for sugar in urine 

 and is employed in the preparation of certain azo dyes, as is also beta-naphthol. 



The naphthols act in general like the phenols, but the (OH) group reacts 

 more readily than in the phenols. Thus, it can easily be replaced by the amido 

 (NH 2 ) group. Naphthols readily form sulphonic acids, of which many are 

 known and are used in the manufacture of azo dyes. The 1, 4, naphthol-sul- 

 phonic acid is used most. 



Beta-naphthol benzoate, C 6 H 5 COOC 10 H 7 (Benzoyl-naphthol},\& obtained by the 

 action of benzoyl chloride on beta-naphthol at 170 C. It is a white crystalline 

 powder, melting at 107 C., tasteless, odorless, and insoluble in water, but solu- 

 ble in alcohol, chloroform, and hot ether. It splits into beta-naphthol and 

 benzoic acid in the intestines. 



Beta-naphthol-bismuth (Orphol] has approximately the composition, C 10 H 7 O.- 

 Bi 2 O 2 (OH), and is said to be formed by the action of an alkaline solution of 

 naphthol on a solution of bismuth nitrate in dilute glycerin. It is a light- 

 brown, odorless, almost tasteless powder, insoluble in alcohol as well as water. 

 In the intestines it splits into naphthol and bismuth hydroxide. 



Alpha-amino-naphthalene, C 10 H 7 .NH 2 (Alpha-nap hthy famine], is obtained by 

 the reduction of the corresponding nitro-naphthalene, the chief product of the 

 action of nitric acid on naphthalene in the cold. It is also formed by heating 

 alpha-naphthol with the ammonia compound of zinc chloride. It melts at 

 50 C., has a pungent odor, and turns red in contact with air. It is easily 

 soluble in alcohol, and forms crystalline salts with acids, the solutions of which 

 with oxidizing agents give a blue precipitate, which soon turns red. 



