718 GIBBS. 
apply, for the solution must be heated almost to boiling before 
the color characteristic of formaldehyde appears. 
Since the article was written a milk preservative called “Sol- 
dona,’’* and consisting of formaldehyde, hydrogen peroxide, and 
water, has appeared upon the market. It looks as if the manu- 
facturers are prepared to take advantage of the difficulties at- 
tending the detection of such a preservative in milk when only 
the Hehner or Leach tests are employed. 
EXPERIMENTAL, 
Solutions of formaldehyde of varying strengths, 3 to 10,000, 
1 to 10,000, and 1 to 100,000, were mixed with equal quantities 
of milk. The concentration of the formaldehyde in the milk 
was then 3 to 20,000, 1 to 20,000, and 1 to 200,000 respectively. 
I have observed that the Hehner test is more delicate when the 
milk is diluted in this way than when more concentrated. Vary- 
ing quantities of hydrogen peroxide were added to these solutions 
in the cold and, after shaking, the Hehner test was immediately 
applied. Some of the results are tabulated as follows: 
TABLE I.—The Hehner test for formaldehyde in presence of varying 
quantities of formaldehyde and hydrogen peroxide. 
‘ion Hommel eee Character of test. 
1} 1 to 20,000 1 to 360 | Yellow. | 
2 1 to 20, 000 1 to 700 | Brown. 
3 1 to 20, 000 1 to 3,000 | Characteristic formaldehyde. | 
4 1 to 20, 000 2 to 3,000 | Reddish purple. Not quite characteristic. 
5 1 to 20, 000 3 to 3,000 | Red brown. Not characteristic. 
6 1 to 20, 000 none | Characteristic. 
7 1 to 200, 000 none | Characteristic. 
8 1 to 200, 000 1 to 3,000 | Red brown. Not characteristic. 
9| 1 to 200, 000 2 to 8,000 | Brown. | 
10} 1 to 200,000 3 to 8,000 | Yellow brown. | 
11 | 1 to 200, 000 4 to 3,000 | Yellow. 
12| 1+to 200,000 5 to 3,000 | Light yellow. | 
en 
In order to show that the failure of the test is not entirely 
due to the reaction between hydrogen peroxide and formaldehyde 
before the test is applied, some of the above mixtures, which 
produced the brown and yellow shades which are not charac- 
teristic, were treated with sodium hydrogen sulphite and sulphur 
dioxide and then immediately tested, with positive results. 
Other mixtures containing larger excesses of hydrogen peroxide, 
treated in the same way, gave positive results. 
“Oskar V. Sobbe, Chem. Ztg. (1911), 35, 1344. 
