6oo 
Journal of Agricultural Research 
Vol. XXVII, No. 8 
Table I.—Effect of uric acid on the determination of lactose by the Munson-Walker- 
Bertrand and the Benedict methods 
PER CENT OF LACTOSE IN SEPARATED MILK 
Uric acid 
added. 
Munson-Walker- 
Bertrand 
method. 
Benedict 
method. 
Gm. 
4. 145 
4. 106 
4. 176 
4. 192 
4. 152 
4. 156 
O. Ol 
0. 10 
°. 90 
I. OO 
“4- 155 
°4- 154 
4. 200 
4. 400 
5- 475 
4- 157 
4. 150 
4. l6l 
4- 173 
® Average. 
It is readily seen from Table I that uric acid markedly affects the esti¬ 
mation of lactose by the combined Munson-Walker-Bertrand method. 
In fact, where i gm. of uric acid was added to a 25 cc. portion of sepa¬ 
rated milk it was impossible to carry out the test. That the Benedict 
method is unaffected by uric acid to any appreciable extent is also shown. 
In a second test about 1,200 gm. of combined excreta from four hens, 
fed on the standard cereal diet, were mixed thoroughly and four portions 
of 200 gm. each removed. To each of two portions, 25 gm. of lactose 
were added and the samples mixed. All four samples were then extracted 
in the same manner with four 300 cc. portions of hot water. Each 
extract was made up to 1,500 cc., mixed, and lactose determined in 
aliquot portions by both sugar methods in the manner in which they are 
used in urine analysis. The results have been averaged and summarized 
in Table II. Table II also contains the averaged results obtained when 
1 and 2 gm. of lactose were added to excreta in a manner similar 
to that when 25 gm. were added. The reducing substances were deter¬ 
mined by the Benedict method only in these cases, however. 
Table II .—Recovery of lactose added to excreta 
Sample of 
lactose. 
Total reducing substances calculated as lactose. 
Munson-Walker-Bertrand 
method. 
Benedict method. 
I. 
II, 
I. 
II. 
Gm . 
Gm. 
Gm. 
Gm. 
Gm. 
0 
0-34 
°- 35 
O.03 
O. 04 
25 
25.81 
26. 21 
24. 86 
25* 13 
1 
(•) 
(0) 
1. 08 
I. 11 
2 
(°) 
( «) 
2. 30 
2. 21 
! 
a Not determined. 
