CINNAMIC ACID. 867 



is yellow, becoming brown in air, with the odour of cinnamon, 

 and a sweet and burning taste, its density 1.008 at 77? boiling 

 point 428 ; it becomes solid at 23. It is slightly soluble in 

 water, and the solution produces with iodine and iodide of 

 potassium, reddish brown crystals, of a metallic lustre, contain- 

 ing, according to Dr. Apjohn, KI + 6 (CiH, I). The oil 

 dissolves completely in potash, and affords on distillation an 

 oil, lighter than water C 18 H 10 O 2 , while the residue contains 

 cinnamate of potash, and a black matter (Mulder). The bleach- 

 ing chlorides convert essence of cinnamon into benzoic acid. 



Cinnamic acid, HO + C 18 H 7 O 3 =HO + CiO. This acid is 

 formed by the oxidation of the essence of cinnamon in air, or by 

 dissolving the oil of the balsam of Peru in an alcoholic solution 

 of potash, evaporating to dryness, dissolving the residue of 

 cinnamate of potash in boiling water, and liberating the cinna- 

 mic acid by an excess of hydrochloric acid. The cinnamic acid 

 crystallizes on cooling in tufts of crystals, which are colourless, 

 and have an aromatic and very acrid taste. The crystals fuse 

 at 264.2 (129 centig.) enter into ebullition at 554, and distil 

 over as a heavy oil, which fixes on cooling ; they sublime at a 

 lower temperature. Cinnamic acid is less soluble, both in cold 

 and hot water, than benzoic acid, which it considerably resem- 

 bles ; very soluble in alcohol and ether; from alcohol it crystal- 

 lizes in large rhomboidal prisms, which are hard and very 

 friable. It may be distinguished from benzoic acid by nitric 

 acid, which converts it into hydruret of benzoyl and nitro- 

 cinnamic acid ; cinnamic acid also does not combine with sul- 

 phuric acid as benzoic acid does. The salts of cinnamic acid 

 are monobasic, and have a great analogy to the benzoates. (Du- 

 mas and Peligot, Mulder). 



Nitro-cinnamic acid, HO + C 18 H 6 O 3 , NO 4 ; produced by the 

 abstraction of H O from the elements of cinnamic acid and nitric 

 acid. This acid is prepared by adding cinnamic acid in powder 

 to strong nitric acid, preventing the temperature from rising 

 above 140. The cinnamic acid is at first dissolved ; the 

 mixture soon becomes hot, and a crystalline substance sepa- 

 rates; the latter is washed with water, dissolved and crys- 

 tallized from alcohol. Nitrocinnamic acid is white with a shade 

 of yellow, fuses at 518; heated above that temperature, it 

 boils and is decomposed. This acid is almost insoluble in 



2 L L 2 



