1918.] The N.Z. Journal of Science and Technology. 245 
Creosote. —Beech, with full-cell treatment with the creosote available— 
namely, grade 2 — gave best results compatible with cost, but empty-cell 
treatment with higher-grade oil would prove more economical. Apart 
from comparison with the following there is nothing of importance. 
Zinc Chloride. — This salt gave fairly good results, the maximum weight 
of dry salt for F. Menziesii being J lb. per cubic foot. The results agree well 
with United States tests, and would seem to offer a cheap means of treatment 
in localities where the rainfall is not too great, this latter precaution being 
necessary owing to the solubility of this salt. So far as one can judge, how¬ 
ever, F. Menziesii is a poor structural timber from other points of view, 
and, since cost is the chief consideration, straight zinc treatment would 
prove more economical than creosote, owing to lower initial cost. I would 
suggest the following as a method of treating fencing-posts. It corresponds 
to a full-cell treatment with zinc chloride, and for the purpose would be just 
as efficient and much cheaper than creosoting. 
The butts of the posts are to receive a preliminary two-hours boiling in 
any cheap crude oil, which expands the air in the cells and thoroughly heats 
the timber to the centre. The posts are then to be withdrawn and imme¬ 
diately immersed in the zinc-chloride (3 per cent.) solution, at ordinary 
temperature. 
Another way, though less efficacious, would be to soak the posts in a 
6-per-cent, solution for at least one week. According to my tests this would 
give about J lb. per cubic foot of dry salt; the other method would give as 
much as \ lb. per cubic foot. 
Of course, the foregoing only applies to the poorer grades of fencing- 
timber. 
For railway-sleepers full-cell zinc has been suggested, but this may be 
modified by injecting an emulsion of 3 parts zinc salt and 1 part creosote for 
wet localities. 
A comparison of costs of different methods adopted in the United States 
of America is here given, culled from different sources :— 
Cost of treating sleepers, 7 in. by 9 in. by 8 ft., exclusive of season¬ 
ing : zinc chloride, 5d. to 7d. per sleeper; zinc and creosote emulsion, 
6d. to 8d. per sleeper ; empty-cell (final vacuum) creosote, Is. OJd. to 
Is. 2Jd. per sleeper; full-cell creosote, Is. 7Jd. to Is. l(>Jd. per sleeper. 
For purposes of comparison these figures apply equally to treatment of 
our own timbers. 
Zinc Chloride and Aluminium Sulphate. —From the results obtained, this 
mixture does not seem to be indicated as possessing any special value. It 
is supposed to give greater penetration than zinc alone, but does not in 
these experiments show any advantage. 
Sodium Fluoride.— This salt gave surprising results, as will be seen from 
the tables. This preservative had just been suggested, and tests inaugurated 
before the war, by the German Government railways. It was hinted then 
that good results were anticipated owing to the high toxicity of the salt, 
which exceeds that of zinc chloride and phenol. It does not have such 
corrosive properties, nor does it attract moisture, and an even more important 
feature is its sparing solubility in water. About J lb. per cubic foot gives 
results which, while not comparable with full-cell creosote, are greatly superior 
to zinc. 
Powellizing Solution. — The results obtained seemed little better than 
the controls, as even rimu with full-cell treatment rotted completely. 
Evidently the arsenic which was added to the sample from the Railway 
