(Contribution from the Basic Sciences Research Department, U. S. Naval 

 Civil Snr-ineering Research and Z;valuation Laboratory) 



FURTHER IMVESTIGi^TIO^' OF BHIBITION OP i"iARINE BORERS BY TREATING ";00D 

 TTH INSOLUBLE COIIPOUITDS OF TKi: HEAVY IiETALS 



ty E. R. Holden and Herbert LIcKennis, Jr. 



In the field of inorganic treatments for the preservation of rrood ag;ainst 

 the destructive activities of niarine organisms, two groups of cornpounds, 

 the various forms of iron oxides and the sulfides of certain heavy metals, 

 are of special interest. The potential us3fulne3s of the iron compounds 

 is based primarily on the kna\'n fact that rusting iron nails afford effec- 

 tive protection to wood (1,2). The second group of compounds, the heavy 

 metal siilfides, have bsen selected as a subject of investigation because 

 of the knovm toxicity of the compounds of the particular metals, the ex- 

 tremely lavi solubilities of the sulfides, and their probable resistance 

 toward losses through oxidation processes. 



In general, the wood is imnregiiated with a solution of a soluble salt and 

 then treated with a second material to precipitate an insoluble heavy 

 metal compound. The natural resins have been observed to exert an influ- 

 ence on, and sometimes apcear to prohibit, these reactions. In an effort 

 to circumvent such difficulties, as arise from participation of wood, 

 c'-'emically or physically in these reactions, different methods and reactants 

 which normally produce the same desired compound have been used. Pertinent 

 basic studies relative to compound formation are being conducted also, so 

 as to provide essential information for the performance tests. 



The standard test block for panels which are placed in harbor ■.rater is 

 2" X I;" X 12" in size. In some cases splints approxim.ately 2|-" x 2" x t" 

 are treated simultejieously for use in a co perative program wherein 

 accelerated tests (3) are being conducted at the liarine Laboratory, Univer- 

 sity ox ]iiami, under the direction of Dr. F. C-. alton Smith. For a given 

 treatment, nine blocks (2" x U" x 12") are nlaced in the v/ater in order 

 that blocks may be removed after intervals of tivne for internal inspection 

 without terminating the test. 



IRON OXIDES 



There are seven important allotropic forms of ferric oxide i^c-j '^- > snd 

 ■?^-monohydrates, the corresponding anhydrous 'X- and -y- forms, the hydrous 

 oxide^, and magnetite (considering magnetite to be a double oxide of ferric 

 and ferrous oxides in a'-roxinately equimolar ratio). In the normal "rusting" 

 or slow oxidation of iron gradual step changes are believed to occur v/ith 



^The "hydrous oxide" may be, actually, a hydrozide (6). 



K - 1 



