Section III, 1918 [149] Trans. R.S.C. 



An AgricuUural Source of Benzoic Acid 

 By p. J. Moloney, M.A., and Frank T. Shutt, D.Sc, F.R.S.C. 



Summary 



(Read May Meeting, 1918) 



The two chief sources of the benzoic acid of commerce are (1) 

 toluene and (2) gum benzoin: from the first is manufactured, by 

 oxidation, practically all the benzoic acid used in the coal-tar industry 

 and from the second is obtained, by sublimation, that employed in 

 pharmacy and as a food preservative. 



The price of benzoic acid is five or six times higher than it was 

 previous to the war and the thought occurred to one of the writers 

 that it might be possible to find a cheaper source in the urine of the 

 herbivorae, provided one or other of the methods that have been 

 proposed, and to some extent used, could be so simplified that the first 

 stages could be conducted on the farm, without any special apparatus. 



Scheele obtained benzoic acid from cow's urine in 1785, 

 Liebig, in 1829, demonstrating that it was not present as such in the 

 urine, but was formed by the decomposition of hippuric acid. The 

 fact therefore that benzoic acid could be obtained from the urine of 

 the herbivorae has been known for more than a century, but the fact 

 has been one of scientific interest rather than commercial import- 

 ance.^ 



Benzoic acid has been prepared from urine by three methods: 



(l)The urine is allowed to putrefy in order to induce the hydro- 

 lytic decomposition of the hippuric acid into benzoic acid and glyco- 

 coll according to the equation: 



NHC7H5O NHo 



CHs^' + H2O = CH,(^ -f C6H5COOH 



^ COOH \COOH 



Milk of Lime in then added, the solution filtered and the benzoic acid, 

 after concentration of the filtrate by evaporation, precipitated with 

 strong hydrochloric acid. 



(2). The putrefied urine after addition of milk of lime is treated 

 with CO2. This removes the excess of lime. Ferric chloride is now 



^Benzoic acid from this source has been characterized by a slight odour of urine, 

 "removed or concealed by mixing the acid with a small quantity of gum benzoin 

 and subliming it." 



