14 BULLETIN 145, U. S. DEPARTMENT OF AGRICULTURE. 
olatile constituents. It also appears that the factor of safety in 
zince-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. 
Tn 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 aalvelile in studying the most 
eficient use of wood preservatives. 
