30 BULLETIN 333, L T . S. DEPARTMENT OF AGRICULTURE. 



the Southern States 1 (PL XIV, fig. 1). After many years' service 

 there may be a deterioration in the treated wood. Other chemical pre- 

 servatives are in use, but coal-tar creosote is usually the most effective 

 preventive since it is also a fungicide and will not leach out in wet 

 situations. For permanent timbers to be used in coal mines a pres- 

 sure process with zinc chlorid has been found more suitable, accord- 

 ing to tests conducted by the Forest Service. 



CABINET WOODS. 



Impregnation of cabinet woods, furniture, etc., with chlorinated 

 naphthalene 2 is effective in rendering wood more resistant to termite 

 attack; treated, perishable, northern cabinet hardwoods comparing 

 favorably with untreated teak and mahogany after two and one- 

 half years' test. 



WOOD-PULP PRODUCTS. 



Treatments have been tested for wood-pulp products, such as 

 the various wood-fiber, " processed," or " composition " boards used 

 for interior finish and as substitutes for lath, etc., when they are to 

 be used in the Tropics and portions of the southern United States to 

 prevent attack by white ants. It has been found that the practical 

 method is to add various poisons during the manufacture of these 

 boards. 



Experiments with such poisons and insecticides as white arsenic, 

 bichlorid of mercury, zinc chlorid, copper sulphate, sodium fluorid, 

 phenol, and dihydrogen potassium arsenate (KH 2 As0 4 ) have been 

 conducted by manufacturers upon the recommendation of the Bureau 

 of Entomology. It has been determined that Avhere insoluble chem- 

 icals were added in the process of manufacture of the board there 

 was so low a retention that the cost rendered the treatment commer- 

 cially impossible. Also in the manufacture of the board a large 

 amount of water is employed which it is not practicable to save, and 

 consequently a large amount of chemical, whether soluble or insoluble, 

 is carried away. As yet the results of these tests do not warrant the 

 drawing of definite conclusions. 



Dihydrogen potassium arsenate is a powerful insecticide, 3 is soluble 

 in cold water, and should prove as effective as the insoluble white 

 arsenic. Sodium fluorid has been been proved, by experiments of 

 A. L. Quaintance, an effective insecticide and is also being tested as 



1 In the Tropics and along the Gulf coast of the United States, where seasonal checking 

 of timber is liable to occur after treatment and setting, a penetration sufficient to 

 prevent white ants from infesting the timber through these checks should be secured. 

 A more uniform penetration with a practical minimum to allow for checking, and 

 a heavier impregnation (at least 15 pounds per cubic foot) are necessary. The depth 

 of penetration can be determined roughly by the thickness of the sapwood. 



2 Process devised by the Western Electric Co., of New York. 



3 Information on this insecticide was obtained from the Branch of Southern Field Crop 

 Insect Investigations from the experiments of B. R. Coad. 



