1918.] The N.Z. Journal of Science and Technology. 239 
precipitation of zinc borate within the pores of the wood, and if excess of 
chloride over the amount required for complete precipitation as borate is 
taken a considerable degree of fireproofing is obtained, in addition to anti¬ 
septic treatment against decay ; and since zinc borate is insoluble in water 
the method is especially applicable to timber for use in bridges, particularly 
road-bridges common in county-engineering work, where first cost might 
argue against creosote, and fire-resistance is desirable owing to the danger 
from grass-fires. 
ANTISEPTIC TREATMENT OF NEW ZEALAND TIMBERS. 
An investigation of the efficiency of various antiseptic methods was 
undertaken, the scheme adopted being a modification of that proposed by 
Chapman (American Society for Testing Materials). The data to be gathered 
were—(1) The class of wood-preservative most efficacious in preventing 
decay in native woods exposed to the action of damp soil and the air ; 
(2) the most efficient method of application of the preservative ; (3) relation 
of nature of timber to efficiency of different methods of treatment. 
Methods of Application. 
A metal cylindrical container for the preservative was made in this 
case from stout galvanized iron, measuring in. in diameter and 13 in. 
high. Specimens were cut with a \ in. saw-cut in the top, and were 
suspended in the preservative by being threaded on to a metal holder by 
means of the slit. Four specimens were treated at a time. 
Three methods of treatment were used—namely, cold dip, hot dip, and 
saturation. Cold dip is considered equivalent to a brush coat with cold 
materials. The specimens are immersed for fifteen seconds in the cold 
liquid and then hung up to allow the surplus to drain off. The temperature 
of the preservative for this treatment is about 21° C. 
The hot-dip treatment is deemed equivalent to the hot open-tank treat¬ 
ment as commonly used in practice. The specimens are immersed for one 
minute in the hot liquid and then hung up to drain. The temperature of 
the preservative for this treatment is about 100° C., except in those cases 
in which the preservative boils or gives off vapour at this temperature. In 
such cases the temperature is reduced only enough to prevent boiling. These 
are solutions of inorganic compounds and one or two low-boiling distillates. 
Saturation treatment is intended to produce the same degree of penetra¬ 
tion in these small specimens as would be produced by the closed-tank 
pressure treatment of full-sized timbers. The specimens are kept immersed 
in the hot liquid for one hour, allowed to cool in the liquid, and then hung 
up to drain. The temperature for this treatment is maintained at 105° C., 
except where the preservative boils at a lower temperature, in which case 
the temperature is kept just below the boiling-point of the liquid. Because 
of the comparatively small size and thickness of the specimen it is probable 
that something approaching the full-cell treatment results from this method. 
Tests and Descriptions of Preservatives used. 
In order that the results of the fungus-bed tests should carry a standard 
value, it was deemed necessary that the preservatives used in this connection 
should be accurately defined by chemical analysis, and the necessary data 
are therefore given in case it should be necessary at any time to correct 
any erroneous impression regarding the efficacy of any of the preservatives 
