182 ELEMENTARY FORESTRY. 



this account more liable to wash out of the wood when in con- 

 tact with the soil. 



inc Tannin Process. In this process the chloride of zinc 

 is protected from being washed out of the ties by coagulated 

 albumen. The process is as follows: The ties are impregnated 

 with chloride of zinc mixed with a small percentage of dissolved 

 glue. They are then subjected to heavy pressure, after which the 

 solution is drawn off and a tannin solution added at a pressure 

 of 100 pounds. This material combines with the glue, and forms 

 a leathery, waterproof substance which permanently closes the 

 pores or outer cells of the wood, excluding moisture and retain- 

 ing the zinc. 



Burnettifcing. In this process the timber is impregnated 

 with chloride of zinc, the operation being similar to that of creo- 

 soting. It has a wonderful preservative effect upon the timber, 

 the only objection to it being that the solution is liable to be 

 washed out of the ties. This is overcome in the modern treat- 

 ment of the ties in Germany by using a certain per cent of dead 

 oil with it, as previously noted in describing the method of 

 impregnating railroad ties. 



Fire-Proof Wood. It has been known for many years that 

 wood could be made fire proof by filling it with certain chemicals 

 in much the same way that railway ties are impregnated. The 

 most common chemical used for this purpose was phosphate of 

 ammonia, and it is perhaps the best material for this purpose 

 that has ever been used, but it is so expensive that the use of it 

 is quite impracticable. The next best material that has been used 

 for this purpose is sulphate of ammonia, but like phosphate of 

 ammonia this somewhat injures the flexibility of the fiber and 

 corrodes metal, and in addition deadens the color and causes the 

 wood to be more hydroscopic. These chemicals, either alone or 

 combined, have given some very good results, but have not been 

 entirely satisfactory. They have been used in fire-proofing war- 

 ships, where great results have sometimes been realized, as, nota- 

 bly, in the war between China^and Japan, where this treatment is 

 said to have given Japan a great advantage in the greatest naval 

 battle of that war. If a fire-proofing process were discovered 

 that combined the merits of cheapness without injuriously affect- 

 ing the qualities of the wood, it would be much sought after, and 



