TESTS OF WOOD PEESEEVATIVES. 



(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. 



(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 Lofflunds malt extract and 20 grams agar-agar. 



The medium and preservatives were sterilized at 100° C. in separate 

 sealed containers, then thoroughly mixed together and poured into 

 petri dishes 100 mm. in diameter and 10 mm. deep. (See PI. V.) 

 After hardening, the agar-preservative mixture was inoculated at the 

 center with the mycelium of a wood-destroying fungus (see PI. 

 V), 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 intervals 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 

 is open to certain objections, such as the possible chemical combi- 

 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 

 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- 

 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 

 for 1 week. The difference in the weight of the steel before and after 



1 Concentrations in this table are based on the actual weight of preservative in 20 c. c. agar-preservative 

 mixture. 



