14 



FORMALDEHYDE. 



Formaldehyde solution was used in six cage experiments, but on no 

 open piles. Three concentrations were tried, by mixing 1 part of 

 the commercial 10 per cent formalin with 3, 6, and 12 parts of water, 

 respectively. The results of three of these tests are given in Table 

 IT. Series E. together with the corresponding controls. In three 

 experiments not given in the table the infestation of the manure 

 was so slight that it was not possible to form any judgment as to 

 the larvicidal action of this chemical. Even in the experiments 

 which are given in the table, the manure was lightly infested. How- 

 ever, all the concentrations show considerable larvicidal action. Tak- 

 ing the average total number of flies of the controls it is evident that 

 from 75 to S5 per cent were killed. It is probable that if this treat- 

 ment had been made in clo>ed boxe> or receptacles to retard the 

 Loss of formaldehyde by evaporation, the larvicidal action would 

 have been still higher. 



As might be expected, the formaldehyde in these dilutions caused 

 a great reduction in the number of bacteria. The highest dilution 

 I 1-1:2) killed 99. G per cent of the bacteria that would grow on beef 

 agar. The chemical results show a decreased alkalinity of the water 

 extract. The ammonia results average slightly higher than those 

 obtained on the control samples, but in Xo. 2. where the dilution 

 of formaldehyde used was 1-G. the bacterial count, the water-soluble 

 nitrogen, the ammonia, and the alkalinity are higher than in either 

 of the other two treated samples. The fact that formaldehyde pro- 

 duces an acid reaction, either by conversion to formic acid or by 

 combining with amino acids, a reaction used by Sorensen (1907) 

 for the quantitative estimation of the amino acids, may explain the 

 reduced alkalinity of these extracts. Nitrites and nitrates were de- 

 tected in all three cases of the manure treated with formaldehyde. 

 It is interesting in this connection to note that Eussell and Buddin 

 ( H>13) carried out some experiments on the action of various volatile 

 antiseptics in the soil, and found that formaldehyde increased the 

 production of nitrates and ammonia. While formaldehyde is ex- 

 tremely disagreeable to work with on account of the irritating action 

 which it has on the mucous membrane, nevertheless further work with 

 this chemical will be undertaken. 



