494 Missoioi AgylcuUuiul Report. 



a contraction of the air and water left in the wood. A partial 

 vacuum is thus formed and atmospheric pressure forces the liquid 

 into the cellular and intercellular spaces. A small portion is also 

 absorbed by the cell walls. The hot bath merely prepares the 

 wood for absorbing the creosote and the actual impregnation fol- 

 lows as the preservative cools. The ease and effectiveness with 

 which the timber is impregnated by this process depends on the 

 kind of wood and its degree of dryness. A porous wood which has 

 been seasoned not less than six weeks is most easily treated. 



If a single tank is used the cooling bath may be given by allow- 

 ing the temperature to fall after it has been maintained for an 

 hour or two at about 220° Fahrenheit. It is better to employ two 

 tanks, one for giving the hot bath and the other for the cold one. 

 The tanks for the hot bath may be two barrels connected by a 

 short pipe, the heat being applied to the pipe, the heating of creosote 

 being brought about by convection currents. Or it may be a heavy 

 iron tank heated by a direct fire. 



Creosote may be purchased from the Barret Manufacturing 

 Company of St. Louis. Their quotations in January, 1913, were 

 as follows, f. 0. b., St. Louis: 



10 gallon cans, 20 cents per gallon. 



Barrels, $8.00 per barrel. 



5 barrel lots, $7.50 per barrel. 



Most species will absorb too much creosote if very long treat- 

 ment is given. To make the treatments economical, the absorption 

 must be limited to 0.4 gallons per post if only the butt is treated 

 and 0.6 gallons if the top is impregnated also. The best treatment 

 is that which will give, with a reasonable absorption, the deepest 

 possible penetration of the oil into the wood in the shortest time. 



The following statements taken from forest service investiga- 

 tions show the saving in money due to treatment with creosote : 



An untreated loblolly pine post costing 8 cents or 14 cents 

 when set in the ground, will average a life of two years. At 5 

 per cent compound interest the annual charge against this post is 

 7.53 cents. The same post if given a treatment costing 10 cents, 

 and this is rather high, will cost, when set, 24 cents. Its life will 

 be 18 years. At 5 per cent compound interest the annual charge 

 will be but 2.04 cents. This shows a saving of 5.49 cents per year 

 on each post. With 200 posts per mile, there is a saving of about 

 $11 on each mile of fence per year. 



