COPPER-PHOSPHATE MIXTURES AS SUGAR REAGENTS. 
A QUALITATIVE TEST AND A QUANTITATIVE TITRATION METHOD. 
FOR SUGAR IN URINE. 
By OTTO FOLIN anp W. S8.:McELLROY. 
(From the Biochemical Laboratory of Harvard Medical School, Boston. 1 
(Received for publication, January 25, 1918.) 
In connection with a previous investigation! it was observed 
that alkaline phosphates can hold copper hydroxide in solution. 
So far as we know phosphates have never been used as a solvent 
for copper hydroxide in the preparation of reagents for sugar, 
yet it was thought that phosphates might possess distinct advan- 
tages for these purposes. They are less expensive than tartrates, _ 
citrates, or glycerol, they do not reduce sugar, and they tend to 
regulate the degree of alkalinity at a lower level of hydroxy] ion 
concentration than is obtained by carbonates alone; a given 
amount of sugar should consequently reduce more copper in such 
solutions. 7 
The serviceability of phosphates in the preparation of copper 
reagents for sugar was soon demonstrated, but they can be used 
in so many different ways that it has been rather difficult to de- 
cide which combination to adopt. (Potassium salts have been 
excluded on account of their cost.) 7 
Qualitative Test for Sugar in Urine.—One good copper-phosphate 
reagent is made as follows: Dissolve 100 gm. of sodium pyrophos- 
phate (vu. s. P.), 30 gm. of crystallized disodium phosphate, and 
50 gm. of anhydrous sodium carbonate, in about 1 liter of water. 
To this solution add 13 gm. of copper sulfate previously dissolved 
in about 200 ce. of water. The solution seems to keep indefinitely, 
except that in cold weather some phosphate may crystallize 
out. The reagent should therefore not be left in very cool places, 
although 19 makes little or no difference whether a small part of 
1 Folin, O., and Denis, W., J. Biol. Chem., 1916, Xxvl, 477. 
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