6 BULLETIN 145, U. 8S. DEPARTMENT OF AGRICULTURE. 
The test pieces were then submerged in a glass jar containing 300 
ce. ¢. of distilled water at room temperature. This water was changed 
at stated intervals and analyzed for the presence of preservative. 
The total time of leaching was 4 weeks. To check the amount of pre- 
servative remaining in the wood after the total submersion period the 
specimens were shredded and chemically analyzed. Owing to the 
large amount of preservative which adhered to the surface of the wood, 
and the absorption of some of it, it was extremely difficult to secure 
satisfactory results on leaching. For this reason no values are given. 
Recent experiments indicate that not only do the different salts 
leach at different rates, but also various concentrations of the same 
salt. 
INFLAMMABILITY TESTS. 
The crib and shaving tests frequently used in testing the combusti- 
bility of wood proved unsatisfactory, and a new form of apparatus 
was finally developed with which more comparable results were 
obtained. This apparatus (see Pl. IV) consists of a silica tube, 
wrapped with nichrome ribbon. An iron tube fitted with a mica 
sight was cemented below the silica tube. 
The specimen of wood, after being lowered in the silica tube, was 
heated at a uniform rate by passing 24 amperes of electric current - 
at 110 volts through the nichrome ribbon. Temperature readings 
were obtained from a thermocouple placed beside the specimen and 
reading direct from a Hoskins pyrometer indicator. <A pilot light 
was used to ignite the gases distilled from the wood. Compressed 
air partially dehydrated by expansion was passed through the appa- 
ratus, its intensity being indicated by a sensitive iquid manometer. 
Three untreated test specimens cut from stick 11 (see Pl. I) were 
burned as a check against the three treated specimens cut- from 
stick 138. When the preservative was a water-soluble salt, the test 
specimens were first air-dried and then oven-dried before ignition. 
When the preservative was an oil, one inflammability test was made 
within 24 hours after impregnation and another after three months’ 
seasoning in the volatility apparatus, the latter being made on speci- 
mens cut from stick 12.1 
TOXICITY TESTS. 
Because of the importance of toxicity tests and the inherent 
objections to various established methods of testing, three independen 
methods were followed: 
(1) Petri-dish method, in which the preservative is mixed with a 
culture medium and inoculated with fungi. 
1 Stick 12 was used for leaching tests in the treatments with water-soluble salts, and for inflammability 
tests after 3 months’ seasoning in the volatility apparatus in the treatments with oils. 
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