copper sulfide formed by the reaction di.d not appear to be very great. 

 Since the influence of the i/ood and its natui-c'il i^esins is not readily 

 amenable" to control , the sulfides have been precipitated in the wood by 

 several procedures using both hydrogen sulfide and ammonium sulfide in an 

 effort to fully test thQir relative, merits. 



Solubilities of Metal Sulfides 



Thr: solubilities of the sulfides in pure v/ater as calculated by Kolthoff 

 (llO and Ravitz (l^) are given in Table 3. IVie most important factor 

 affecting the solubility of a sulfide is the hydrogen ion concentration, 

 the solubility being proportional to the square- of this value. Since the 

 pH of sea v;ater is usually greater than 7 this would favor even lower 

 solubilities than in pure water. The solubilities should be of the same 

 order of ma^r^'nitude , though they may be actually somewhat greater than in 

 pure fater because of the solvent action of the salts in sea virater. 



Performance Test's 



'.•^ihile large numbers of treated blocks are now in the water it is too early 

 to make any appraisal of their durability vrith the exception of copper 

 sulfide. The blocks v;ith a surface treatment having a maximum penetra- 

 tion of about 1/8 of an inch ^vere unattacked in the first year at Port 

 Hueneme but are being infected no^T near the end of the secod year. Uni- 

 formly treated blocks are now in the water along with the various other 

 metal sulfide treatments for better evaluation of the protective value. 



sun iiHY AND CONCLUSIONS 



Studies have been made of the chemical and physical properties of the 

 various forms of iron oxide and the metal sulfides relative to their use- 

 fulness as wood presei'vatives. 



It has been possible to impregnate wood with certain forms of iron oxide 

 that are believed to be intermediates in the normal oxidation of metallic 

 iron under sea water conditionc. The experimental findings as to the con- 

 ditions affecting the formation of these oxides have been as follows.* 



(1) The y'-f erric oxide raonohydrate can be obtained by oxidation of the 

 precipitate resulting from the addition of either ammonium or sodium 

 h^J-droxide to ferrous sulfate when the rate at which the hydroxide is 

 added is regulated by means of the pH value for the heterogeneous 

 mixiture. 



(2) The precipitation of a ferrous salt by a base produces- particles which 

 have a higher pH reaction than the solution in which they are suspended. 



K - 8 



