6s8 



Journal of Agricultural Research 



Vol. VI, No. 17 



TREATMENT OF THE VIRUS WITH FORMALDEHYDE 



Although formaldehyde destroys the infective principle of the virus 

 in certain concentrations, peroxidase is not appreciably injured for a 

 considerable time at much greater concentrations. Loew (15, p. 20) 

 has shown that the peroxidase of tobacco is unaltered in a 5 per cent 

 solution after 48 hours. It appears that some oxidases also are very 

 resistant to formaldehyde. Kastle (13) found that the oxidase of the 

 mushroom Lepiota americana is not destroyed by a 40 per cent formic- 

 aldehyde solution which is allowed to act for several days. In the 

 writer's test (Table VI), the peroxidase of tobacco was not appreciably 

 changed in 1 per cent solutions of formaldehyde after standing 30 days. 

 In these tests a 37 per cent U. S. P. solution of formaldehyde was used. 

 All concentrations were made on the assumption that 2.5 c. c. of this 

 solution contained about 1 gm. of formaldehyde. The virus was filtered 

 through paper to remove all suspended material. To subject the virus 

 to a certain strength of formaldehyde, a water solution of formaldehyde 

 just twice as strong as desired for the virus was made up. Equal parts 

 of this solution and the virus were then mixed, thus bringing the formal- 

 dehyde strength down to that required for the virus. In this way the 

 virus was uniformly diluted to one-half its original strength in all con- 

 centrations of formaldehyde. 



Table VI. — Infectivity of the mosaic vims after 31 days' treatment with formaldehyde 

 in 191 5, 10 plants having been used in each test 



Experiments carried out in 1914 with unfiltered virus treated with 

 the same strengths of formaldehyde and tested 32 days later gave prac- 

 tically the same results. In these tests the virus still retained its infec- 

 tious properties in that solution which contained 1 part of formaldehyde 

 in 1,000 parts of virus solution. All stronger solutions had lost the 

 power to produce infection. 



