December, '21] snyder: white-ant- proof wood 497 



moisture-proof. The cost of this treatment is justified by this double 

 effect and the fact that cabinet woods impregnated with this chemical 

 can be advertised as white-ant-proof. 



Wood-pulp products also can be rendered white-ant-proof by adding 

 poisons in the process of manufacture. 



Naturally Resistant Woods 



In 1912 the Branch of Forest Entomolog}^ of the Bureau of Ento- 

 mology, U. S. Department of Agriculture, began a series of tests of the 

 relative effectiveness of treatments with chemical wood preservatives 

 against attack by white ants at a field station at Falls Church, Va. 

 In connection with these experiments, other service tests of the relative 

 resistance of various native and tropical untreated woods to attack by 

 white ants were begun in 1913. 



The preliminary^ results of these tests, which are as yet incomplete 

 and not conclusive, give some data of value. Certain species of wood 

 appear to be naturally highly resistant to attack by white ants. This 

 is not due to the element of hardness, since these insects will attack the 

 hardest known wood, Lignum-vitae, but due to the presence in the wood 

 of substances such as oils, alkaloids, etc., which are repellent or dis- 

 tasteful to white ants. 



Normally the wood of pines is most susceptible to attack by white 

 ants, but in case of certain pines with an extremely resinous heartwood, 

 such as the "fatwood" of longleaf pine {Pimis palustris) of the southern 

 United States, this is immune to attack by white ants; the excess of 

 resin is a preventative. There is also some inherent principle in the 

 heartwood of the red cedars (species of Juniperus) which renders it 

 distasteful to white ants. 



Species of native woods which might be used as veneers over chemically 

 treated woods, or as ply or laminated woods, are listed in Table I, with 

 their distribution in the United States, and their relative resistance to 

 attack by white ants. 



A few species valuable or which miglit prove useful for other purposes 

 are also listed in this table. 



Chemical Treatments for Finished Forest Products 



The treatment for cabinet woods is impregnation with chlorinated 

 naphthalene — a crystalline wax — by placing it in open vats of the wax, 

 at a temperature of from 220 to 240° F., without previous dr>nng of the 

 wood'. The wood remains in the vats for periods varying with the 

 dimensions of the wood; wood of >^ inch thickness requires but 15 

 minutes. 



'Process devised by the Western Electric Company of New York, N. Y. 



