ELECTRICAL BATHS FOR USE WITH BENEDICT'S 

 METHOD FOR THE DETERMINATION OF UREA 



WILLIAM H. WELKER 



(Laboraiory of Biological Chemistry of Columbia University, at the College of 

 Physicians and Surgeons, New York) 



(With plates 8 and 9) 



INTRODUCTION 



Benedict's well-known and excellent method for the determina- 

 tion of Urea was first published in a preliminary report in 1909.^ 

 Early in the year of Dr. Benedict's associateship in this laboratory 

 (1909-10), the technic of his method was improved by Dr. Gies's 

 suggested use of a porcelain beaker instead of a glass beaker as the 

 Container of the sulfuric acid which Dr. Benedict preferred for the 

 bath.2 At Dr. Gies's request, Dr. Benedict taught the method to 

 advanced students in this laboratory prior to the füll publication of 

 the details of the method,^ and Miss Olive G. Patterson used it 

 regularly about the same time in a research under Dr. Gies's direc- 

 tion on the partition of urinary nitrogen after external hemorrhage.* 

 Other advanced workers here also had occasion to use the method 

 now and then, before its detailed publication. 



During the progress of Miss Patterson's research (during April, 

 May and June, 1910), Dr. Gies found it expedient to devise a num- 

 ber of further improvements in the technic of the method. A lead 

 cap, with perforations large enough to admit the test tubes, was 

 placed over the porcelain bath. This cap obviated the unsatisfac- 

 tory use of clamps attached to the side of the beaker and inserted 

 into the mouths of the tubes. Jena test tubes, 6 X M in. in diam- 

 eter and bulbous (i^ in.) an inch below the mouth,^ were used 



^Benedict: Proceedings of the American Society of Biological Chemists, 

 1909, i, p. 225; also Journal of Biological Chemistry, 1909-10, vii, p. xii. 



^Benedict: Journal of Biological Chemistry, 1910, viii, p. 418. 



'Benedict: Ibid., p. 405. 



*The results of this research will be published at an early date. 



'Bulb tubes, such as those numbered 4,877 in the latest Eimer and Amend 

 general apparatus catalog, were selected. 



439 



