II. CHEMISTRY 



465 



Similar reactions occur with other acids. Nicotinic acid nitrate' melts 

 at 184 to 185°. The picrate of nicotinic acid separates from absolute alcohol 

 in modular aggregates of short rhombic prisms which melt at 221 to 222° 

 to a red oil which begins to decompose at 250°.' This compound contains 

 65.5 % picric acid.' 



OH 



-COOH OoN 



\N/ 



NO, 



—COOH 



H+ 



+ 



NO 2 



NO. 



Nicotinic acid (and nicotinamide) react with methyl iodide and similar 

 alkyl iodides to yield compounds which are readily soluble in water (see 

 p. 492). 



COOH 



+ CHjI 



-COOH 



\N/ 



CH, I 



(2) Properties associated with its acidic character ; 



Salt formation occurs when nicotinic acid is treated with alkali or an 

 alkaline earth hydroxide. The ammonium, sodium, potassium, calcium, 

 magnesium, etc., salts are readily formed as white crystalline solids by 

 titration of the acid with the hydroxides, viz.: 



-COOH 



+ NaOH 



\N/ 



-COONa 



+ H2O 



\n/ 



Heavy metal salts convert nicotinic acid to the metallic nicotinates. 

 This property has proved useful in recovering nicotinic acid from reaction 

 mixtures^^ and from dilute nicotinic acid solutions, since salts such as 

 copper nicotinate are quite insoluble at certain pH values. Nicotinic acid 

 (and nicotinamide) reacts with HgCl2 to form insoluble chloromercurates 

 which crystallize in characteristic forms. Gautier®^ has proposed the use of 

 this reaction as a means of microchemically characterizing nicotinic acid 

 and nicotinamide. Nicotinic acid will react with mercuric acetate as shown 

 in the following equation. 



=« F. C. Huber, U. S. Pat. 2,487,874 (November 15, 1949). 

 " J. A. Gautier, Ann. chim. anal. 26, 89 (1944). 



