THE INTERFERENCE OF HYDROGEN PEROXIDE WITH THE 
MILK TESTS FOR FORMALDEHYDE. 
By H. D. Grpss.* 
(From the Laboratory of Organic Chemistry, Bureau of Science, and the 
Department of Chemistry, University of the Philippines, Manila, P. I.) 
The Hehner and Leach tests both depend upon the color which 
formaldehyde produces with milk proteids in the presence of 
iron salts and strong acids, the former with sulphuric and the 
latter with hydrochloric.2 These reactions are both very deli- 
cate, the latter showing the presence of formaldehyde in the milk 
when in the proportion of 1 to 250,000. Hehner’s reaction is 
perhaps not so delicate, but with proper manipulation is 
extremely satisfactory. 
I have constantly employed these reactions by mixing the 
solution to be tested with an equal volume of fresh cow’s milk. 
In the climate of Manila I have observed that better results are 
obtained by cooling the solutions and the milk before mixing. 
While studying the reaction between methyl alcohol and 
hydrogen peroxide® it was observed that both of these reactions 
failed absolutely in many cases where there was every reason 
to believe that formaldehyde was present and the Rimini reac- 
tion was positive. Mixtures of formaldehyde with milk in vary- 
ing proportions from 1 to 3,300 to 1 to 200,000 were prepared 
and tested by both reactions. Small quantities of hydrogen per- 
oxide were then added and the tests immediately repeated, with 
negative results. Instead of the characteristic violet or purple, 
the only colors obtained were yellow and brown. 
In the dilutions employed, formaldehyde is not oxidized by the 
hydrogen peroxide before the test is made. The explanation of 
the phenomenon is to be looked for in the effect upon reactions 
with the proteids which produce the colored compound, or it is 
possible that the heat generated by the contact of the sulphuric 
acid in the Hehner test is responsible for the destruction of the 
formaldehyde by the hydrogen peroxide at the zone of contact 
where the characteristic color should appear. After the hydro- 
gen peroxide is removed by reducing agents, the positive test 
can be obtained. In the case of Leach’s test the same arguments 
* Associate professor of chemistry, University of the Philippines. 
*For an extensive study of this reaction, see Voisenet, Bull. Soc. chim, 
Paris (1905), 33, 1198. 
* See the preceding paper. 
77 
