TESTS OF WOOD PRESERVATIVES. 7 
(2) The injection of the preservative into wood, with a subsequent 
exposure to pure cultures of wood-destroying fungi in sterilized jars. 
Specimens recut from stick 14, as indicated in B, Plate I, are being 
used for these tests. 7 
(3) The injection of the preservative into wood with subsequent 
exposure to various fungi in a fungus pit. Specimens recut from 
sticks 1 to 6, inclusive, as indicated in B, Plate I, are being used for 
these tests. ; 
At present tests by the petri-dish method are the only series that 
have advanced far enough to be reported upon. 
PETRI-DISH TESTS. 
In these tests the culture medium consisted of the extract of 1 
_ pound of lean beef in 1,000 c. c. distilled water, to which is added 25 
- grams Léfflunds malt extract and 20 grams agar-agar. 
The medium and preservatives were sterilized at 100° C. in separate 
sealed contamers, then thoroughly mixed together and poured into 
petri dishes 100 mm. in diameter and 10 mm. deep. (See Pl. VY.) 
After hardening, the agar-preservative mixture was inoculated at the 
center with the mycelium of a wood-destroying fungus (see Pl. 
VY), and the cultures then placed in an incubator held at approxi- 
mately 25° C. for from 4 to 6 weeks. The growth was observed 
usually at mtervals of about a week. Plate V shows the appearance 
of these cultures of fungi in various stages of development. This test 
- is considered by the Forest Service as merely tentative. While it 
it is open to certain objections, such as the possible chemical combi- 
2 nation of certain of the preservatives or their constituents with the 
- media, it nevertheless offers considerable advantage in giving quick 
indications of the toxicity of a substance, in that way indicating the 
_ most promising preservatives for further work. 
_ The results of tests to date on the fungi Fomes annosus (Fr.) Cke. 
and Fomes pinicola (Sw.) Fr. are summarized in Table 5.1 
CORROSION TESTS. 
| 
| 
| 
| 
| To determine the corrosive action of the preservative on steel, so 
ie that possible deterioration in a treating cylinder might be ascer- 
| tained, a strip of boiler flange steel of the quality specified by the 
| American Society for Testing Materials, August 16, 1909, was sub- 
ls merged in the preservative and heated to a constant temperature of 
| -about 98°C. The preservative was changed every week for 4 weeks 
in the case of oils; with aqueous solutions, it was changed every day 
- for1 week. The difference in the weight of the steel before and after 
rx 1 Concenirations in this table are based on the actual weight of preservative in 20 c. c. agar-preservative 
ay cf . b 
- mixture. 
