12 BULLETIN 145, U. S. DEPARTMENT OF AGRICULTURE. 
times as much so as coal-tar creosote. Sapwood antiseptic was 
almost nontoxic. 
Preservatives designated as copperized oil, fuel oil, Tmbereaphele | 
kerosene, and N.S. Special had very low toxic properties. 
CORROSIVE ACTION OF THE PRESERVATIVE ON FLANGE STEEL. 
Of the various preservatives tested, coal-tar creosote, copperized 
oil, the fractions of coal-tar creosote, the various carbolineums, the 
water-gas-tar products, fuel oil, Timberasphalt, and kerosene had- 
very slight corrosive action on steel. In practical operations such 
action can very probably be neglected. 
The metallic salts, except cresol calcium and sodium fluoride, were’ | 
much more pronounced in their action than coal-tar creosote, so that 
the depreciation in plants using them would seem to be much greater. 
The corrosive action of eresol caleium is much less than the other | 
salts tested. Zinc suiphate was much less corrosive than zine chloride. 
The very marked corrosion of hardwood tar, Preservol, and tar 
from Douglas fir is probably due to the comparatively large amount 
of acetic and other organic acids which they contain, while the some- 
what less corrosive action of Spirittine and beechwood creosote are 
probably due to smaller quantities of these acids. 
In general, wood-tar products were much more corrosive than coal- 
tar or petroleum products. This property may, however, be largely 
eliminated in the future development in methods of refining these oils. 
DISCOLORATION OF PAINTED WOOD. 
All of the oils tested rendered the wood unfit for subsequent paint- 
ing. Copperized oil was least objectionable in this respect. If 
thoroughly dried after treatment, so that excess 011 would not appear 
on the surface, it is possible that wood treated with some of these 
_ preservatives foal be satisfactorily painted with dark pigments. 
The water-soluble salts were all satisfactory (except sodium silicate - 
and cresol calcium) in that they caused no discoloration and appar- 
ently no deterioration of the painted surface. From the results of 
tests thus far made it is likely that woods treated with zime chloride 
and many water-soluble salts can be successfully painted. ; 
Cresol calcium caused discoloration of the paint; sodium silicate 
reacted with the oil of the paint film, causimg it to lose its adhering 
properties. 
Additional tests on the effect of zine chloride and sodium fluoride 
on white-lead paint were made. Specimens exposed to the weather 
were in good condition after 24 months, when they were accidentally 
destroyed. Specimens placed in moist air were in good condition 
after 1 year and 4 months. No difference was noticeable between 
1 This applies, of course, only to the method of painting herein described. 
