14 BULLETIN 145, U. S. DEPABTMENT OF AGBICULTUEE. 



volatile constituents. It also appears that the factor of safety in 

 mic-chloride treatments is very low, and that to secure the best re- 

 sults more than 0.4 to 0.5 pound per cubic foot, the present practice, 

 should be injected. 



' In general, the flash or burning point of an oil affects the inflam- 

 mability of wood treated with it. Of greater importance, however, 

 is the length of time the treated wood has seasoned, as a prolonged 

 seasoning of such wood raises considerably its ignition temperature. 

 It would seem good practice first to season such treated timber before 

 placing it in positions subject to fire. While wood treated with the 

 water-soluble salts mentioned in these tests was in general less diffi- 

 cult to ignite than untreated wood, nevertheless the presence of such 

 preservatives usually renders the wood slow burning and easily ex- 

 tinguishable. 



In using the data submitted in this bulletin, the reader is cautioned 

 against drawing sweeping conclusions. It was possible to make only 

 a limited number of check determinations because of the many 

 variables which had to be considered. The most reliable information 

 on the efficiency of preservatives is, of course, obtained from service 

 tests, but until such data become available, it is thought that the 

 tests already described will be found valuable in studying the most 

 efficient use of wood preservatives. 



