182 ELEMENTARY FORESTRY. 
this account more liable to wash out of the wood when in con- 
tact with the soil. 
Zinc 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. 
Burnettizing. 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 Chinayand 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 
