632 



AMERICAN FORESTRY 



the large list of preservatives which 

 have been tried, long experience has re- 

 duced the number which are of accepted 

 value to two ; namely, coal tar creosote 

 and zinc chloride. In 1910 the con- 

 sumption of creosote in the United 

 States totalled 63,266,000 gallons, of 

 which 38,640,000 gallons, or 69 per cent, 

 were imported ; while zinc chloride was 

 used to the extent of 16,802,500 pounds. 

 The latter, which is a soluble mineral 

 salt, leaches out of the wood in wet 

 climates, and is of greatest value in 

 arid regions. Creosote is the preserva- 

 tive most generally used, present de- 

 velopments indicating the decreasing 

 rise of zinc chloride alone ; although in 

 mixture with creosote, or with some 

 heavy oil as a seal, it promises excellent 

 results. 



The methods or processes by which 

 preservatives are introduced into wood 

 involve many technical details which 

 are not of general interest. Preserva- 

 tives are applied by pressure, open tank, 

 and brush application. Of these the 

 first is of greatest value and most wide- 

 ly used, open tank and brush treatments 

 being superficial and of value mainly 



where low cost is essential and facilities 

 for thorough treatment are not avail- 

 able. 



The usual type of wood-preserving 

 plant is equipped with from one to five 

 heavy boiler plate cylinders, from six 

 to seven feet in diameter and about 

 130 feet long. The additional equip- 

 ment necessary to operate the plant in- 

 cludes steam boilers, pressure and 

 vacuum pumps, air compressor, storage 

 tanks, etc. The cylinder has a heavy 

 door which can be tightly closed by 

 heavy pivoted bolts, tight-fitting gaskets 

 preventing the escape of the preserva- 

 tive under pressure. The ties or timber 

 for treatment are loaded on narrow- 

 gauge steel cylinder cars, and a whole 

 train usually fifteen cars is run bod- 

 ily into the cylinder ; tracks being pro- 

 vided inside the cylinder and the cars 

 designed so that they just fit the avail- 

 able space. The heavy door is then 

 closed and the hot creosote introduced 

 from overhead tanks. Pressure is then 

 applied and increased up to 160 to 2<>o 

 pounds per square inch, or until the 

 desired amount of absorption is ob- 

 tained. The oil is then dropped into 



CROSS SECTIONS OF BEECH TIE TREATED BY THE REUPIXG PROCESS AT STEXDAL, 



GERMANY. 



