1890-91.] Dr Haycraft on Uric Acid in the Urine. 
255 
On the Estimation of Uric Acid in the Urine. A Reply 
to Criticisms upon the Silver Method. By John 
Berry Haycraft, M.D., D.Sc. 
(. Physiological Laboratory , University of Edinburgh.) 
(Read February 16, 1891.) 
(Abstract.) 
I published in the Brit. Med . Jour., December 12, 1885, a 
method invented by me for the easy and yet accurate estimation 
of uric acid. The method consists in precipitating the uric acid 
as a silver salt, estimating the silver, and calculating the uric acid 
from the silver (168 uric acid to 108 silver). As no process was then 
invented which had itself been tested, except as Salkowski’s, by the 
side of others acknowledged to be inexact, I did all my work with 
weighed quantities of uric acid, and tested my process — the only 
straightforward way of working — by adding known quantities of 
uric acid to one of two samples of a urine, and finding as a result 
of my estimations of the uric acid in the two samples practically 
the same difference as the weight of acid added. Hermann con- 
firms my work (Zeitsch. f. physiol. Chemie , Bd. xii. s. 496), 
and Czapek, working with Professor Huppert, proposes a modifica- 
tion of my method, while Camerer’s results (Zeitsch. f. Biologie , 
Bd. xxvii. s. 113) run on parallel lines. My results have been 
adversely criticised by Salkowski, who still maintains that uric acid 
and silver do not combine in a definite ratio. This observer 
published in 1872 twelve analyses, which show, according to his 
belief, that there is no constancy in the proportion between the 
silver and uric acid, and in 1889 he again affirms the same 
thing, bringing forward in proof of his assertion some dozen 
analyses made by his colleague Professor Jolin and himself. I was 
for some time unwilling to take up the controversy where Professor 
Salkowski had left it, for, certain of the care with which my own 
work had been done, I was quite willing to let the matter be 
settled by other and less prejudiced persons, especially as such 
seemed willing enough to undertake the task. As, however, my 
method had been widely used, especially for clinical purposes, and 
