30 



BULLETIN 227, U. S. DEPARTMENT OF AGRICULTURE. 



normal growth is also relatively slow as compared with that of the 

 other organism. Sometimes on high concentrations of toxic media 

 the fungus would remain dormant from four to seven weeks and then 

 begin a slow development. For this reason it has been difficult in 

 many cases to find the exact inhibition point of a preservative with- 

 out carrying out a large number of long-continued tests. 



On the other hand, Forties pinicola seems rather sensitive to slight 

 changes in concentration, and one can usually judge within a month 

 whether the fungus will develop. 



The difference in behavior between these two organisms shows 

 how very necessary it is to make only qualified statements when dis- 

 cussing the relative toxicity of preservatives toward fungi. We have 

 at present no satisfactory way of predicting, except by trial, how a 

 given preservative will react on different organisms. 



A direct comparison of toxicities, as given in Table II, shows that 

 in many cases essentially the same order holds, but there are several 

 exceptions. Fractions I and IV of coal-tar creosote and zinc chlorid 

 being the most conspicuous. 



In Table III the oils used are grouped according to their nature, in 

 order to show a direct comparison between wood tar, coal tar, water- 

 gas tar, and petroleum products. 



Table III. — List of wood-preserving oils tested, showing relation between their specific 

 gravities, boiling points, and toxic properties. 



[Results marked with an asterisk (*) are approximately correct.] 



Preservative. 



Specific 

 gravity. 1 



Percentage distilling below — 



Killing point (per 

 cent). 



180° 



c. 



215° 



c. 



245° 

 C. 



275° 

 C. 



305° 

 C. 



320° 



c. 



360° 



c. 



Fomes 

 annosus. 



Fomes 

 pinicola. 



Wood tar (hardwood) 



1. 195 *27 



*31 

 *31 



*10 



12.8 



17.8 

 78.3 

 30 

 .9 



51 

 54.7 



37.7 

 44.4 











*1.25 

 *65 



40+ 



*65 



.55 

 .30 



0.75 



1.052 



1.058 



.995 



1.018 

 .934 

 1. 003 

 1.015 

 1. 088 

 1.150 



1. 126 



1.127 



.937 



*16 



*7 



3.3 



4.8 

 35. 1 

 *2_3 











*.20 



United Gas Improvement 

 Co. 1.07 oil, No. 1101 



Water-gas tar distillate No. 

 2235 



16.3 

 61.7 

 54.1 



*22 

 75.3 

 67.2 



*27 

 80.3 

 74.1 



56.4 



40+ 



Coal-tar creosote: 



.225 





.225 





16.2 

 .9 



*92 

 49.2 



4.7 













77.7 

 38.5 



4.1 



16.4 



85 



54.3 



10.1 



*29 



*30 



30.2 



48.7 

 *S0 



*.325 

 *3.30 

 *33 



5.25 



4.5 



40 



.125 





*.125 





*7.S 



Avenarius carbolineum (sp. 

 gr. at 16.5° C.) ■ 



S. P. F. carbolineum (sp. 

 gr. at 16° C.)... 





1. 1 



2. 6 

 *9 

 *3 



6.1 



.30 



Copperized oil (sp. gr. at 



L'5° C.) 





*2 



*10 



*22 



40+ 







1 At 60° C. except as stated for the last three preservatives. 



It is interesting to note that the wood-tar and low-boiling water- 

 gas tar and coal-tar distillates tested show very similar toxic prop- 

 erties, while the carbolineums, which consist in the main of the 

 high-boiling constituents of coal-tar creosote, in all cases proved 

 much less toxic to the fungi used. 



