the effective life of such paints. Briefly, most of these paints ov^e 

 their antifouling properties to the slov; solution of a copper compound 

 in seawater. In order to screen the numerous paint formulations an 

 accelerated test method v.-as devised, whereby the copper dissolves at approx- 

 imately 100 times the average rate in seaviater. This test thus provides 

 a roughly quantitative measure of the period over ^vhich a paint may be ex- 

 pected to release copper in concentrations sufficient to maintain its anti- 

 fouling qualities. 



In the case of antifovling paints it has been fo-und that increasing the pH 

 of seawater will bring; aboiit accelerated leaching of the^cepper. A 'similar 

 test for vrood preservc,.tives designed to repel marine borers xfRS sought, 

 with its principal objective the testing of preservation by creosote and 

 its chemical and physical fractions. In the initial tests creosote was 

 used to impregnate slips of clear sourthern pine, l/8 inch in thiclmess. 

 The impregnation viras made by Dr. Sweert!^ of the Naval Research Laboratory, 

 as part of a cooperative project. A large supply of creosote was purchased 

 in order that a permanent standard could be used for this and all subse- 

 quent experiments. This is novj- referred to, at least informally, as U. S. 

 Experimental Creosote Standard Number i. 



The vrooden slips vfere e".posed to various treatments for the purpose of 

 leaching out the preservative in order to simulate the natural loss of 

 preservative under service conditions. By using thin slips of wood it 

 was hoped that learning would be more -rapid. An attempt was made to further 

 accelerate by varying the chemical and physical conditions of the leaching 

 bath. 



The initial experiments were carried out in leaching baths at room tempera- 

 ture. Hydrochloric acid and sodium hydroxide w.:re both used to bring about 

 considerable changes in pH of the seawater bath. Other treatments consisted 

 of boiling in seawater and agitation in oxidizing solutions. Controls 

 leached in standing seawater, running seawater and controls with no leach- 

 ing at all were provided for comparison. 



Following the period of leaching, all of the thin wooden slips were immersed 

 in the sea for exposure to marine borers. The results of a typical experi- 

 ment are shown in Table 1. Boiling in seawater alone was successful in 

 leaching out the active toxicant of the creosote treatment to the point 

 where borer resistance was reduced. Acid, alkali, or oxidizing baths were 

 surprisingly less effective. 



These experiments were confirmed by washing leached panels free of the 

 leaching water and placing them in dishes of seawater to which shipworm 

 larvae were added. The results , Table 2, substantially agree with those 

 of the field exposure tests. 



Although boiling in seawater r/as the most effective method of accelerating 

 leaching, it also had the obvious disadvantage that the rates of leaching 

 of the various creosote components might be quite different in the presence 

 of steam than in vrater below boiling point. Later experiments were there- 



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