18 THE SMOKE INVESTIGATION 



was distributed uniformly over the plant. To determine 

 the amount applied, weighings of the soot collected in the 

 crystalizing dishes were made and these computed to 

 unit area. The soot was applied at daily intervals usually 

 extending over about one week. In each experiment four 

 cases were used, one as a control and three for the applica- 

 tion of soot. In order to keep down the temperature in 

 the cases they were protected by shades of cheese cloth. 



ANALYSES OF SOOT 1. 



The samples of soot used had the following analyses 8 : 



Tar Ash Fixed Carbon 



'Sample A. 6.12% 28.1% 65.78% 



Sample B. 6.70% 5.5% 87.75% 



Sample C. 1.12% 26.0% 72.88% 



EXPERIMENTS IN NURSERY AND GREENHOUSE. 



The following experiments will indicate the general 

 results obtained. Care was taken in selecting plants which 

 were similar and in good condition in the beginning of 

 each experiment. 



EXPERIMENT I. 



Begun July 2, 1912. Selected Jack Pine seedlings in 

 the College nursery. Applied small quantities of soot July 

 2, 3, 4, 11, 12. Continued experiment until July 23. Quan- 

 tities of soot of sample A used as follows : In case No. 1, 

 2.412 gm. per square meter. No. 2, .438 gm. per square 

 meter. No. 3, .438 gm. per square meter. No. 4, Control 8 . 



(1) Volatile matter refers to that portion of the dried sample 

 which was driven off by heating in a tightly closed platinum crucible 

 in the full flame of a Bunsen burner for seven minutes. The residue 

 remaining in the crucible is coke. This is burned by heating in the 

 air, and the percentage of ash is determined. The percentage of coke 

 minus the percentage of ash gives the percentage of fixed carbon. 



(2) All of the analyses were furnished by the Industrial Re- 

 search Laboratory of the University of Pittsburgh and were made 

 under the supervision of Dr. R. C. Benner. 



(3) Applications of .438 gm. per square meter is sufficient to 

 make a continuous black coating over the entire plant. 



