ANTISEPTIC TREATMENT OF WOOD. 



517 



temperatures of 112 to 194 F. (50 to 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. 310), and the latter are pushed 

 along a tramway (in, in, Fig. 309) into the cylinders /I, .1. 

 When the cylinders are full, the rails leading to them are 

 removed, and the head x adjusted and fixed firmly so as to 

 close the cylinder. The wood is first steamod ;it a temperature 

 of 112 C. (234 F.) for one 

 hour ; the steam is con- 

 ducted from the boiler .17 

 through the steam-pipe a. 

 When the steaming process 

 is concluded, the air is 

 sucked out of the wood by 

 means of the air-pump /> 

 and the injecting liquid 

 (30 to 50 fold diluted chloride 

 of zinc, the latter contain- 

 ing 25% of zinc) is admitted 

 through the pipe 1> b into 

 the cylinders, the air-pump 

 still working for some time. 

 AYlien the cylinder is full, 

 the forcing-pump 7> presses 

 the liquid into the wood. 

 In order to effect this, a pressure of about 6 atmospheres is 

 applied for :, ! to 1 \ hours. The injecting liquid is then drawn 

 back into the reservoir, and the truck removed with its con- 

 tents. The two cylinders are used alternately. 



Quite recently it has become the practice to omit the steam- 

 ing entirely and to dry the wood, especially in creosoting with 

 tar-oil, etc. This method is employed in Berlin and also 

 by the Great Northern Eailway, Ireland. The drying is 

 effected in a drying-chamber, heated to 177 or 267 F. The 

 wood is then placed in the injecting cylinders, out of which 

 the air is drawn, and the tar-oil admitted at a temperature 

 of 113 to 140 F. (45 to 60 C.), and pressed into the wood 

 in the same way as when chloride of zinc is used. 



Fig. :U<>. Front of an injecting cylinder 

 with a truck laden with wood. 



