4 BULLETIN 145,.U. S. DEPARTMENT OF AGRICULTURE. 
PENETRANCE OF THRE PRESERVATIVE INTO WOOD. 
The distribution of a preservative in the wood, a most important | 
feature in any treatment, was studied as follows: 
The central portions of sticks 4, 5, and 6, after the strength data | 
had been obtained on them, were split, and the depth and character _ 
of the penetration recorded. This could usually be done -visually, _— 
but with those preservatives which in aqueous solution were color- 
less, an anilme dye was used or the specimens were | 
eiyaed: ; 
The results from these tests were used to supplement those secured 
from pieces 8, 9, and 10, which were tested in a specially-constructed 
penetrance apparatus (see Pl. II) operated in the following man- 
ner: A hole 1 inch in diameter was bored in the center of each stick 
(A) to a depth of three-fourths inch. The stick was then placed on 
the shelf (8) inside the apparatus for several hours, and after being 
weighed was clamped between two iron disks (Cand D) so that the 
preservative could be forced into the hole from the tank (#) under 
a constant pressure and temperature. The stick was raised to a 
temperature of about 180° F. by the steam coils ( #’) before the pre- 
servative was admitted. The pressure was controlled by compressed 
air on the top of the preservative in tank (#). For oils, the length 
of the pressure period was 30 minutes, and for water-soluble salts 3 
minutes, with the exception of sodium silicate, for which the time 
was prolonged to 30 minutes. The time it took to penetrate the 
wood longitudinally was noted.? At the end of these periods the 
specimen was sawed longitudinally and transversely through the 
center lines and the penetration radially, tangentially, and longitudi- 
nally was studied. (See Pl. III.) 
VOLATILITY TESTS. 
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The volatility tests on oils were made to determine only the 
relative rates at which they left the treated wood. The plan of 
using matched pieces, as outlined in Plate I, was abandoned because 
the data obtained were inaccurate, the specimens reabsorbing 
moisture through the untreated end surfaces of the specimens cut 
after treatment. A new set of specimens was prepared from noble 
fir (each 114 by 2 by 6 inches) and treated for the volatility experi- 
ments. These were weighed separately and placed in the volatility _ 
apparatus (fig. 1), consisting of an air-tight metal box, 15 by 24 by ~ 
30 inches, through which a constant current of air, partially dehy- 
drated by passing through calcium chloride towers, was drawn. 
1It was found by repeated tests that water and the dye had a tendency to penetrate in some cases 
slightly farther than the preservative, although the difference was of no practical significance. . 
2 A mirror placed in the back of the apparatus enabled the penetration in the rear end of the stick to ‘be 
determined. 
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