306 morey: benzoic acid as standard 



CHEMISTRY.— Benzoic acid as an acidimetric standard. George 

 W. Morey. Communicated by W. F. Hillebrand. To 

 appear in the Bulletin of the Bureau of Standards. 



The study of the suitability of benzoic acid as a primary 

 standard in acidimetry and alkalimetry was suggested by experi- 

 ence gained in the purification of benzoic acid to be used as a 

 calorimetric standard. During that work it was found that 

 benzoic acid could be titrated with standard alkali to a high 

 degree of accuracy and that this titration afforded the most 

 rapid and accurate method of comparing the purity of various 

 samples. Since pure benzoic acid has been furnished for some 

 time by the Bureau of Standards as a calorimetric -standard, 

 it would of course be advantageous to use it also for a standard 

 in acidimetry if found suitable. 



Wagner, 1 in a report presented to the Fifth International 

 Congress of Applied Chemistry, in 1903, mentioned benzoic acid 

 among a number of other possibilities for the purpose named; 

 and Phelps and Weed 2 included it in a short study of the availa- 

 bility of several organic acids and acid anhydrides. 



The method used in studying this problem was that of stand- 

 ardizing a hydrochloric acid solution by several well known 

 and standard methods, and comparing the results so obtained 

 with those obtained by standardizing the same hydrochloric acid 

 against benzoic acid. The methods chosen for the work were 

 the distillation method of Hulett and Bonner, the gravimetric 

 silver chloride method, comparison with a sulfuric acid solution 

 standardized gravimetrically by the barium sulfate method, and 

 comparison with the same sulfuric acid standardized volumetri- 

 cally by the sodium oxalate method. All the materials used 

 were prepared with the greatest care, and were carefully pro- 

 tected from the carbon dioxide of the air by suitable guard- 

 tubes. Great care was taken to prepare and keep all solutions 

 free from carbon dioxide, and each solution was tested from time 

 to time for the presence of carbonate. All operations were con- 



1 Proc. Fifth Internat. Cong. Applied Chemistry, Berlin, 1 : 323. 1903. 



2 Am. Jour. Sci. 26: 141. 1908. 



