Biological Chemistry. 



derivatives of the former can be obtained only by the direct 

 action of the metal itself, with evolution of hydrogen 



and the products thus obtained are decomposable by water 



the metallic derivatives of the acids can be obtained by the 

 action of the caustic alkalis and other bases, and are stable 

 in the presence of water (or undergo decomposition only to 

 a minor extent, especially when an excess of alkali is 

 absent). 



The salts derived from formic acid are known as 

 formates, and those of acetic acid are known as acetates. 

 The free acids themselves can be designated as hydrogen 

 formate or hydrogen acetate respectively, and the termina- 

 tion ate is used generally in connection with salts of these 

 acids. 



If they contain a hydroxyl group it might also be 

 surmised that this should be replaceable by a halogen. As 

 a matter of fact, when these acids are treated with phos- 

 phorus halogen compounds the expected reaction takes 

 place, and a series of well-defined products of the general 

 formula R-COC1, R-COBr are obtained when the acids are 

 treated with phosphorus pentachloride or bromide. 



These reactions should indicate, therefore, the existence 

 of a hydroxyl group, and the formulae of the acids can 

 therefore be expanded from R-C0 2 H into R-CO-OH. 

 The formulas of the salts of the monad metals would be 

 R-CO-Oif. 



In addition to the method of preparation of the acids 

 by the oxidation of aldehydes, there is also another very 

 important one which indicates their genetic relationship to 

 other substances. Cyanides (or nitriles, as they are some- 



