40 
Indian Forest Records. 
[Vol. III. 
As to the relative value of the various antiseptic solutions which can 
be used in the Open Tank method, they will be dealt with in detail here¬ 
after. 
Intensity oe Treatment. 
By the intensity of treatment is meant the duration of the period of 
immersion of the timber, the temperature to which it is heated and the 
strength of the solution. As stated above, soft woods require a shorter 
period of immersion than hard woods. 
The various companies in advertising their patent solutions state 
the time necessary for immersion and the temperature to which the 
solution should be raised, they having based their recommendations on 
experiments carried out with such soft species as beech and European 
conifers. From experiments carried out in the laboratory on Indian 
hard woods with some eight or ten patent solutions, after examination of 
the inside of the treated specimens, the conclusion arrived at was that 
in many instances the treatment to be of value, must be of considerably 
longer duration, a solution of greater strength being required, and that 
each different antiseptic calls for treatment according to its own merits 
and limitations. 
Details of experiments will be given hereafter, it being sufficient to 
sav in proof of the above assertion that such soft woods as Boswellia 
serrata and the Indian conifers can be effectively treated by immersion 
in a hot solution for 20 minutes to half an hour, harder timber such as 
“ In ” ( Dijoterocarpus tuberculatus) requires two hours, while immersion 
for a period of four to eight hours is probably excessive in their case; again 
a twenty-four hour immersion of very hard woods such as Fterocarpus 
Macrocarpus (Burman Padauk) appears insufficient. 
The period of immersion must also be regulated by the depth of 
penetration necessary to preserve the timber. This can only be ascer¬ 
tained by experiments carried out in the field and extending over a 
considerable period of time. Probably the penetration into soft timber 
will have to be greater than in the case of hard woods. Provisionally 
it may be stated that in the case of soft woods a penetration of three 
inches on the sides and six inches at the ends will be sufficient to protect 
large pieces of timber, while in the case of hard woods effective protection 
will be obtained bv an absorption to half that depth. 
( H3 ) 
