170 U. S. BUREAU OF FISHERIES 



was prepared, but another test specimen was not substituted because 

 of lack of time. As the experiment progressed it became evident that 

 the "spottiness" played a much less important part than it did at first. 

 A visual examination of the lines treated with this preservative 

 showed that the inequality of the treatment had decreased very 

 remarkably after several weeks, and the lines at the end of the test 

 were as uniform in color as those w^hich had preservatives treated 

 with 2815 and 2818. The explanation of these phenomena appears 

 simple. It is that the excess preservative which was on the outside 

 of the twine dissolved or was removed by currents or friction far more 

 rapidly than was the material found wathin the body of the cord, 

 and that the heavier deposits constituting the "spots" were easily 

 removed and hence disappeared first of all. The material inclosed in 

 the body of the cord is obviously safe from friction and the influence 

 of strong currents and suffers loss only through the process of actual 

 solution. 



The process of solution is very slow in general, as is shown by the 

 very gradual downward slope of the curves 2825, 2815, and 2818 

 after the end of the fourth week. The presence of tar in treatment 

 2818 apparently hampered this process of solution but very little. 

 After the end of the fourth week treatment 2817 did not behave in the 

 same manner as those previously described. The concentration of 

 toxic material in the twine treated with this preservative does not 

 remain nearly constant after the end of the first period, as do the 

 other treatments but decreases with time more rapidly than do the 

 other toxic materials. This may be explained on the basis that 

 copper resinate is more soluble than the organic copper salts used in 

 the other treatments. This w^ould account for the superior degree 

 of protection offered by this treatment, for as long as there is any 

 copper resinate present it will dissolve slowly, but rapidly enough so 

 that there will exist a toxic atmosphere much more powerful than 

 that which would have been supplied by other materials. 



Copper resinate possesses an additional advantage due to the fact 

 that it is possibly more adhesive than copper oleate and not nearly 

 as soft. Hence, it covers the outside fibers of the twine more effec- 

 tively and resists abrasion longer. Some samples of copper resinate 

 have shown a tendency to become brittle and friable after being applied 

 to the twine, but this effect can be neutralized very effectively by the 

 addition of copper oleate to the treatment. 



It seems probable that a mixture of copper resinate and copper 

 oleate will give better satisfaction than either of these materials used 

 alone. The lines treated w4th copper resinate are "wiry" in feel if 

 the material is applied in large amounts. However a treatment 

 containing 1% pounds of copper resinate and 1% pounds of copper 

 oleate per gallon of kerosene, when applied to fine gill thread, leaves 

 it with a softness and flexibility which is apparently near enough 

 the feel of untreated twine to act in the same manner. Copper 

 resinate appears to possess properties which wall enable it largely to 

 replace copper oleate for net preservative treatments. First, it is a 

 low-priced copper salt which is sparingly soluble in water but soluble 

 enough to be poisonous to destructive forms of life; secondly, it has 

 the physical properties which enable it to stay on the fiber much 

 longer than copper oleate; and, finally, it is cheaper and more depend- 

 able than copper oleate purchased in the open market. Preliminary 



