42. RBSOBGIN, PHLOROGLUCIN, ETC. 35 



titles of not much more than 10 grams at one operation, is mixed 

 with 6 to 8 parts of caustic alkali, and introduced in successive 

 portions into a previously heated silver crucible, and the heat 

 continued, stirring occasionally with a silver spatula until the 

 mass is in a uniform state of fusion. After cooling the contents 

 of the crucible are dissolved in water, and a slight excess of 

 sulphuric or hydrochloric acid added. The decomposition pro- 

 ducts, which are specially to be looked for, are butyric and 

 valerianic acid (cf. 25, 34, 139), pyrogallol, phloroglucin, 

 and resorcin, benzoic ( 26), paraoxybenzoic, and protocatechuic 

 acid. The majority of these substances may be removed by 

 ether after acidifying. Volatile fatty acids might be previously 

 extracted by shaking with petroleum spirit. 



Resordn. After the fatty acids have been removed by petroleum 

 spirit, resorcin may be extracted from the aqueous liquid by 

 shaking with ether and distilling the ethereal solution after sepa- 

 ration. It forms crystals melting at 99, has a sweetish taste, and 

 strikes a dark violet colour with solution of ferric chloride, violet 

 with chloride of lime, and rose-red with ammonia. It reduces 

 ammoniacal solution of nitrate of silver. 



Phloroglucin is also very sweektasted, and resembles resorcin in 

 many of its reactions, but is coloured reddish-violet with ferric 

 chloride, and transient reddish-yellow with solution of chlorinated 

 lime. The anhydrous crystals melt at 220. 



'Pyrogallol tastes bitter, is soluble in water, alcohol, and ether, 

 melts at 115, reduces ferric to ferrous salts, colours the latter 

 blue-black, and separates gold, silver, platinum and mercury from 

 solutions of their salts. An alkaline solution exposed to the air 

 rapidly assumes first a red, then a brown colour ; with lime-water 

 it passes through a transient violet and purplish-red tint. 



Protocatechuic Acid has an acid reaction, is sparingly soluble in 

 water, strikes no colour with pure ferrous, but yields a dark-green 

 solution with pure ferric salts. With mixtures of both ferric and 

 ferrous salts a violet tint is produced. The green liquid obtained 

 by the action of ferric chloride is turned red by potash, and then 

 assumes a violet tint on addition of hydrochloric acid. It reduces 

 the metal from an ammoniacal silver solution, but is distinguished 

 from the three foregoing substances by not reducing alkaline tar- 

 trate of copper. With acetate of lead it yields a precipitate 

 soluble in acetic acid. 



32 



