10 
BULLETIN 259, IT. S. DEPARTMENT OF AGRICULTURE. 
Experiment 6. — On the efficacy of formaldehyde solution, TJ.S.P., 
as a preservative against oxidation. Carried out in open 300 c. c. 
Erlenmeyer flasks, earlier experiments having shown that working 
in open beakers led to misleading results owing to loss of formalde- 
hyde by evaporation. Mixtures made and managed in usual way. 
Table 6. — Effect of formaldehyde solution as preservative against oxidation. 
No. of test. 
Per cent actual As 2 3 by 
analysis. . 
Original, j 28 days. 
71 days. 
a (no formaldehyde solution) 
0.205 ! 0.005 
b (0.04 per cent formaldehyde solution) 
c (0.06 per cent formaldehyde solution) 
d (0.08 per cent formaldehyde solution) 
e (0.10 per cent formaldehyde solution) 
.205 j .197 
.205 i .197 
.205 . 
0.005 
.191 
.193 
.205 ! 
.192 
1 
Experiment 7. — On the efficacy of formaldehyde solution, U.S. P., 
as a preservative against reduction. Mixtures made in usual way 
and kept in entirety filled and tightly closed bottles. The content 
of the mixture in total arsenious oxid was approximately 0.21 per 
cent, and no actual arsenious oxid was added except that introduced 
through the bath used to inoculate the mixture. 
Table 
-Effect of formaldehyde solution as preservative against reduction. 
No. of test. 
Per cent actual As 2 3 by analysis. 
! ! ' 
Original, j 5 days, i 12 days. 18 days 
a (no formaldehyde solution) 
b (0.02 per cent formaldehyde solution ) 
c (0.03 per cent formaldehyde solution) . 
d (0.04 per cent formaldehyde solution) 
0.015 0.208 
.015 I .013 
.015 L- 
.015 
0.013 
.013 
0.219 
.210 
.013 
From these series of laboratory experiments it may be concluded: 
(1) Flotation of a millimeter or so of paraffin oil upon the surface 
of dipping baths during periods of disuse may measurably retard 
oxidation. This it possibly does, not by forming a coating imper- 
meable to the oxygen of the air, for oxygen is notably absorbed by 
petroleum oils, 1 but by retarding the rapidity of diffusion of oxygen 
into the bath underneath. Therefore oil might very possibly show 
to much better advantage in field experiments than in the above 
laboratory experiments, and doubtless deserves further study. Con- 
sideration must be given to the possibility of interference with thor- 
ough wetting of animals by a dip so treated and consequent failure 
to kill ticks, therefore the process should certainly not be used until 
1 Compare Comey's "Dictionary of Chemical Solubilities" and Seidell's ''Solubilities of Inorganic and 
Organic Substances." 
