10 



BULLETIN" 259, U. S. DEPARTMENT OP AGRICULTURE. 



Experiment 6. — On the efficacy of formaldehyde solution, U.S.P., 

 as a preservative against oxidation. Carried out in open 300 c. e. 

 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 AS2O3 by 

 analysis. 



Original. : 28 days. 



71 days. 



a (no formaldehyde solution) 0. 205 



b (0.04 per cent formaldehyde solution) . 205 



c (0.06 per cent formaldehyde solution) i . 205 



d (0.08 per cent formaldehyde solution) j . 205 



e (0.10 per cent formaldehyde solution) i . 205 



0.005 

 .197 

 .197 



0.005 

 .191 

 .193 

 .192 



Experiment 7 . — On the efficacy of formaldehyde solution, U.S. P., 

 as a preservative against reduction. Mixtures made in usual way 

 and kept in entirely 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 7. — Effect of formaldehyde solution as 'preservative against reduction. 



• 



No. of test. 



Per cent actual AS2O3 by analysis. 



Original. 



5 days. 



12 days. 



IS days. 



a (no formaldehyde solution) 



0.015 

 .015 

 .015 



.015 



0.208 

 .013 









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." 



