METHODS OF INJECTION. 667 



the bark is not material, as the sapwood dries down for a few- 

 centimeters and becomes impermeable for liquids. 



Another improved method based on that of Boucherie is that 

 carried out by Pfister.* Instead of pressure due to a fall of about 

 30 feet, Pfister used a portable forcing-pump producing a pres- 

 sure up to 20 atmospheres, he thus drove the injecting liquid 

 through tubes into the wood, the tubing being so arranged that 

 it can be lengthened at discretion or conducted at the same time 

 to several logs. The advantages of this method are, that the 

 injection is more rapidly effected than by Boucherie and in the 

 forest immediately after the felling of the trees or poles, without 

 any necessity for transporting them to the injecting works. 



Pfister's apparatus will thoroughly inject a beech-butt 10 feet 

 long in about half an hour, it being immaterial whether the bark 

 is damaged or not. He also devised an improved method of 

 enclosing the base of the logs. The apparatus, with several 

 different sized closing pieces, costs .i>200 to £300. 



(b) Pneumatic injection. — Antiseptic substances can be injected 

 into wood more effectually by means of a forcing-pump than by 

 the hydrostatic method, the process being then much more 

 rapidly conducted : at present pneumatic injection is exclusively 

 employed in Germany in the case of chloride of zinc, creosote, 

 acetic acid, &g. 



In this case the wood is first converted into beams, scant- 

 ling, railway-sleepers, &c., and is then placed in large iron 

 cylinders {A, A) containing the injecting liquid, which, at tem- 

 peratures of 112°— 194° F. (50'— 90" C.) is pressed into the 

 wood by powerful steam forcing-pumps. 



The pieces of wood to be injected are packed as tightly as 

 possible on the trucks (fig. 299), and the latter are then pushed 

 along a tramway {m, m, fig. 298) into the cylinders A, A. When 

 the cylinders are full, the rails leading to them are removed and 

 the head x adjusted and firmly fixed so as to close the cylinder. 

 The wood is then at first steamed at a temperature of 112i C. 

 (234i F.) for one hour ; the steam is conducted from the boiler 

 M through the steam-pipe a. When the steaming process is 



■■' Dimitz uud Bblimerle, Centralblatt des gesamniteu For.stwesens, Vienna, 1889. 



