200 ODOROGRAPHIA. 
from dilute alcohol. According to the reactions which take place 
in this operation, cinnamic anhydride is formed and is then 
decomposed by the boiling with water. When acetic anhydride 
and benzaldehyde are heated together no cimnamic acid is formed, 
benzidene diacetate being in this case the product. The sodium 
acetate therefore acts as a dehydrating agent, or to bring about a 
decomposition of the benzidene diacetate which is first formed. 
Perkin found that the sodium acetate can be replaced by butyrate 
or valerate without affecting the production of cmnamic acid *. 
When benzaldehyde is heated with acetic anhydride, benzidene 
diacetate is formed, as above menticned. If this be heated with 
sodium acetate, cinnamic acid is formed, and can be even more 
readily obtained by Caro’s process of heating benzidene chloride 
with sodium acetate +, the diacetate bemg, however, the first 
product. 
Cinnamic acid is also formed when benzaldehyde is heated to 
140° with malonic acid. Cinnamic acid was formerly prepared 
from liquid styrax, but is now manufactured by the method 
discovered by Caro, which can also be used for the preparation 
of substituted cinnamic acids by the employment of substitution 
products of benzidene chloride f. 
Cinnamic acid dissolves in 3500 parts of water at 17°; it is 
much more readily soluble in boiling water and crystallizes from it 
in lustrous plates, while it separates from alcohol in monosymme- 
tric prisms, melting at 133°. It sublimes in a similar manner to 
benzoic acid, but somewhat less readily, is volatile in steam and 
boils at 300°-304°, but partially decomposes on continued boiling 
into styrolene and carbon dioxide. It yields benzene in consider- 
able quantity on fusion with caustic soda§, while it is resolved 
into benzoic acid and acetic acid when caustic potash is em- 
ployed ||. Oxidizing agents convert it first into benzaldehyde, so 
that it can in this way be readily distinguished from benzoic 
acid §. It is converted into hydrocinnamic acid by sodium 
amalgam and water. 
* Journ. Chem. Soe. 1877, i. p. 838. 
+ Roscoe & Schorlemmer, Org. Chem. iii. pt. v. p. 214. 
{ Ber. Deutsch. chem. Ges. xy. p. 969. 
§ Ibid. xiii. p. 1257. 
|| Ann. Chem, Pharm. lxxxvi. p. 264, and exlvii. p. 112. 
q Ibid. lv. p. 1. 
