1890-91.] Dr Hay craft on Uric Acid in the Urine . 
257 
proves, therefore, is that by his method about 14 mgrms. less uric 
acid are found than by the silver calculation. The mistake he fell 
into in interpreting his results will be obvious on referring to column 
5 of his table. He here calculates the ratio between the silver and 
uric acid found by his method and does not find it constant. The 
reason is very obvious, for in the weaker urines the loss of 14 
mgrms. will be comparatively a heavy loss, making the ratio of the 
uric acid to the silver low, while in the stronger urines the loss will 
be less felt. A glance at the table will show this, for the silver in 
the upper part of the table is say 4T to 3, while in the lower part 
it sinks to say 3*4 to 3. The loss of a pound is much to a poor 
man, but will not inconvenience a rich one, because it bears a small 
ratio to the sum that he possesses. 
In Jolin and Salkowski’ s recent paper the same error is repeated 
without discovery, the table of estimation they give showing still 
more forcibly a “constant difference” as a result of their estima- 
tions. In the last two pages of his article this is shown very 
forcibly in the case of two final experiments made by Salkowski, 
who estimates both the silver and the uric acid (by his method) in 
one and the same urine : — 
No. 
Uric Acid 
reckoned from 
the Silver. 
Uric Acid di- 
rectly estimated 
(Salkowski). 
Difference. 
Ratio between Silver 
and Uric Acid. 
1 
*0756 
•0556 
191 
3-99 : 
: 3 
2 
•0938 
•0757 
18-1 
3*66 : 
3 
He says “Das yEquivalentverhaltniss zwischen Harnsaure und 
silber berechnet sich. Aus Yersuch 1 == 3 : 3 *99 aus Yersuch ii. 
3 : 3 ‘66. Auch diese Bestimmungen bestatigen, also lediglich meine 
friiheren Angaben. It is obvious that the existence of a constant 
difference of about 19 mgrms. (more urine was used than in this case, 
hence the greater deficit) was all he really proves, and this con- 
stant deficit tells most in the case of the weaker urine. Salkowski 
would not have misinterpreted his results had he arranged theiii 
with sufficient care or put in a column of differences which I have 
taken the liberty of adding. His results are therefore valuable 
