18 



BULLETIN 607, U. S. DEPARTMENT OF AGRICULTURE. 



approximately a corresponding absorption with the tar mixtures, the 

 time of treatment was increased above that required for creosote by 

 about 17 * per cent for the mixture containing 25 per cent tar, about 

 60 per cent for the mixture with 50 per cent tar, and 200 per cent 

 for the mixture containing 75 per cent tar. 



After treatment the blocks were split to determine the penetration. 

 Those treated with creosote were completely penetrated, and those 

 treated with the mixture containing 25 per cent tar were fairly well 

 penetrated. A small area at the center of the blocks treated with 

 mixtures having 50 and 75 per cent tar was unpenetrated. Plate X 

 is a photograph of a set of these blocks when split. 



PENETRANCE TESTS. 

 (Data in Table 19.) 



ABSORPTION- LBS. ftVE .LOWGITUDIHAL PEMETR'W -INS, 



JLIMf_QF TRE ATMENT- MINUTES 



m 



i 



— 



— 



— 



- 



.... 



wm 



if 























-- 



wk 



Hi 









m, 



y mm 



75S CREOSOTE 

 25% TAR 



506 CREOSOTE 

 501 TAR 



25 c CREOSOTE 

 75% TAR; 



TAR AND CREOSOTE MIXTURES 



TREATING TEMP. 220° F. 

 PRES.200LBS.PER SQ.IM. 



CREOSOTE 



PRES.& TEMP. VARIED 



Fig. 10.— The relation between absorption, penetration, and time of treatment using mixtures of creosote 

 No. 4 and tar No. 5; also the comparative eSect of varying the pressure and time of treatment. 



PENETRANCE TESTS WITH CREOSOTE NO. 4 AND TAR NOS. 1 AND 5. 



Time of treatment and pressure constant and temperature varied. — 



(Tables 18 and 21 and figs. 11 and 12). 



Two series of tests on the effect of varying the temperature were 

 made, both on the penetrance apparatus. In the first series a mixture 

 of 50 per cent creosote No. 4 and 50 per cent tar No. 1 was used. In 

 the second, 75 per cent of tar No. 5 and 25 per cent of creosote No. 

 4 was used. Both the absorption and penetration were materially 

 increased as the treating temperature was increased. The tests 

 indicated that temperature is an important factor in absorption and 



1 Absorptions in these cases were about 9 per cent higher than with the creosote. 



