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PROTECTING WOODS AGAINST TERMITES. 13 
Timber impregnated with sodium fluorid is apparently as resistant 
to attack by termites as timber impregnated with zine chlorid (stand- 
ard specification one-half pound of dry salt per cubic foot). Sodium 
fluorid, however, is much more expensive than zine chlorid. 
Another method is the “ Kyanizing ” process, consisting of a steep- 
ing treatment with a 1 per cent solution of bichlorid of mercury; 
this chemical, however, is extremely poisonous (see p. 15), which 
may greatly restrict its use. All of the above treatments are effective 
for flooring, interior woodwork, other fixtures, or furniture. 
Impregnation with chlorinated naphthalene is an effective treat- 
ment for valuable cabinet woods or expensive furniture; it is also 
a moisture-retarding treatment. 
Chlorinated naphthalene is a crystalline wax with a melting point 
of about 196° F. It is made in several grades varying in specific 
gravity, melting point, and other characteristics, according to the 
-extent to which the chlorination process is carried. 
The chlorinated naphthalene used in these tests is a mixture of 
various chlorinations as well as free naphthalene, with a large pre- 
ponderance, however, of tri chlor naphthalene. 
This material is usually referred to as tri chlor naphthalene and, 
as compared with other chemicals, it is really comparable to a 
technical product having naphthalene, mono chloro naphthalene, 
di chlor naphthalene, and probably some of the higher chlorinations 
as impurities. Its melting point ranges between 190° and 210° F. 
This is the specification under which it is sold. 
The grade used in these tests, as identified by the melting point 
stated, sells at 836 cents per pound in carload lots; a less refined grade 
can be purchased for 20 cents per pound in the same quantity. 
The samples of wood for test were treated as follows: Blocks of 
the wood 6 by 6 inches by 4 inch were placed, without previous dry- 
ing, in an open pot of the chlorinated naphthalene at a temperature of 
from 220° to 240° F. and allowed to remain fully covered by the 
molten wax for 15 minutes. The blocks of wood were then removed 
and wiped off with a cloth. The treated wood can be stained, shel- 
jacked, and varnished. ‘The resultant color will be somewhat darker 
than the color of untreated wood, and care must be exercised in 
cleaning the surface thoroughly to insure proper adherence of shellac 
or varnish. 
The different woods varied greatly in the amount of wax taken 
up in the above treatment. Furthermore, the amount of wax taken 
up will vary according to the size and condition of the wood treated. 
The blocks carried approximately 5 per cent of wax, or at the rate of 
from 2 to 8 ounces of wax per board foot. At the above price for 
the impregnating material, the treatment would be rather expensive 
and possibly prohibitive for ordinary use, such as flooring. 
The treatment also renders the wood moisture-retarding to a 
marked degree, and its cost is sometimes justified by this double 
effect. 
In the tests of untreated woods and woods that were treated with 
preservatives for use in finished forest products, such as furniture, 
cabinets, etc., experimental blocks of wood from various species of 
both coniferous and broad-leaved trees were buried in the ground 
with logs heavily infested with termites (Reticulitermes spp.) at 
Falls Church, Va. These blocks were 6 inches square by one-half 
