318 BENZYLIC ALDEHYDE. 



remains partially dissolved in the water (aqua amygda- 

 larum amararum, aqua laurocerasi) ; the greater part 

 collects below the water. In order to separate it from 

 hydrocyanic acid, it is shaken with a concentrated so- 

 lution of sodium bisulphite, with which it (like the 

 other aldehydes) combines, forming a difficultly soluble, 

 crystalline compound, C 7 H 5 .S0 3 ^"a -f IJIPO. This is 

 purified by pressing, and washing with alcohol, and 

 then decomposed with sodium carbonate. 



Properties. Colorless, highly refracting, thin oil, of 

 a peculiar pleasant odor. Specific gravity, 1.063. Boil- 

 ing point, 180. Soluble in 30 parts of water. The 

 pure oil, free of hydrocyanic acid, is not poisonous. It 

 combines, like acetic aldehyde, with acetic anhydride, 

 forming a crystalline compound, C 6 H 5 .CH(O.C 2 IPO) 2 , 

 fusing at 45-46 ; the same compound is also formed 

 by the action of silver acetate on benzal chloride. It 

 combines with ammonia and amides with elimination 

 of water. Oxidizing agents convert it into benzoic 

 acid. When distilled with phosphorus chloride or 

 phosphorus bromide, it yields benzal chloride or benzal 

 bromide (p. 274 and 276). Nascent hydrogen (from 

 sodium-amalgam and water) converts it into benzyl 

 alcohol, hydrobenzoin and isohydrobenzoi'n (p. 320). 

 When boiled with an alcoholic solution of potassa, it 

 yields benzyl alcohol and benzoic acid. 



Orthochlorbenzylic aldehyde, C 6 H 4 C1.CHO. Is 



produced by heating orthochlorbenzal chloride (see 

 Salicylic aldehyde, p. 322) with water at 170. Liquid, 

 boiling at 210. 



Parachlorbenzylic aldehyde, C 6 H 4 C1.CIIO. Is 

 produced by conducting chlorine into oil of bitter al- 

 monds, containing iodine ; by boiling chlorbenzyl chlo- 

 ride (p. 275) with a solution of lead nitrate, and by 

 heating chlorbenzal chloride (p. 275) with water. - 

 Colorless liquid, distillable without decomposition. 



Dichlorbenzylic aldehyde, C 6 H 3 C1 2 .CHO, and tri- 

 chlorbenzylic aldehyde, C 6 II 2 C1 3 .CHO, are obtained by 



