6 BULLETIX 101, U. S. DEPARTMENT OF AGRICULTURE. 



glass windows in the front and back. Steam coils J in the bottom of 

 the oven heated the specimens and preservatives to a uniform tem- 

 perature, which duplicated as nearly as possible the temperature 

 conditions of the treating cylinder. The pressure was determined 

 from the gauge G and the temperature from thermometer H. A 

 safety valve K aided in maintaining a uniform pressure. Shelves 

 were provided and specimens were placed in the apparatus previous 

 to testing in order to heat them uniformly to the required tempera- 

 ture. By the aid of mirror D, placed at the back of the oven, both 

 ends of the specimens were made visible. 



The impregnation tests were made in a cylinder 1$ feet in diameter 

 and 4 feet long. Temperature and pressure conditions within the 

 cylinder were accurately regulated by means of steam coils and a 

 pressure pump. A cage was used that held the specimens in a ver- 

 tical position and separated from each other during treatment. 



MATERIALS USED. 



CREOSOTE. 



Coal-tar creosote of a good grade was used, having a specific grav- 

 ity of 1.0483 at 60° C. The viscosity at 60° C. was 1.3, determined 

 by the Engler orifice-type viscosimeter. The distillation range was 

 as follows: 



Per cent. 



0°-205° C 11.0 



205°-255° C 34.9 



255°-295° C 15.8 



295°-320° C 11.4 



Residue 25.8 



Loss 1.1 



The residue was solid with a lustrous fracture, indicating an 

 admixture of undistilled tar. 



WOOD. 



The wood used was obtained from 20 species of conifers. All of 

 the material of each species was taken from the same log, and the 

 specimens were so cut that individual pieces were as similar as pos- 

 sible ; but in most cases both heartwood and sapwood sets were pre- 

 pared. The results obtained on each piece are, therefore, compara- 

 ble with those obtained on other like specimens of the same species. 

 The following species were tested : 



Common name. Botanical name. 



Yew Taxus breuifolia. 



Alpine fir Abies lasiocarpa. 



Eastern hemlock Tsuga canadensis. 



Bis tree Sequoia icashingtonia. 



