40 



IT. S. BUREAU OF FISHERIES. 



Here, as at Woods Hole, the copper paints, Q and R, run very 

 close to the copper oleate and tar combinations. The copper paint 

 No. 2, (R) , containing, as it does, much more copper than No. 1, (Q), 

 stands first; then come the copper and tar combinations, followed by 

 copper paint No. 1. Both the copper paints, however, contain much 

 more copper than either of the copper and tar mixtures. A striking 

 difference from the Woods Hole series (and the other salt-water 

 experiments) is found in the behavior of copper oleate alone and the 

 Dutch method. In all the salt-water tests, without exception, copper 

 oleate preserved better than the Dutch method. Here, however, the 

 Dutch method stands higher, comparing favorably with the copper 

 paints and the copper and tar mixtures, while copper oleate, doing 

 well the first 30 days, afterwards fails rapidly. 



It seems likely that the cause of this peculiar difference lies in the 

 comparative solubilities of the copper compounds present. The 

 Dutch method deposits copper tannate, which appears to remain in 

 the lines; but the copper oleate was not very plainly visible in the 

 lines returning from these fresh-water experiments as it was in the 

 salt-water series. It may be that the copper oleate is too soluble in 

 fresh water and gradually dissolves out, while the tannate is less 

 soluble. If this is so, why the reverse condition of results from salt 

 water ? Copper oleate appears to be less soluble in salt water than 

 in fresh. A certain degree of solubility of the active ingredient may 

 be necessary, for a totally insoluble material may be inert and 

 ineffectual as a preservative. Sea water, being an electrolyte, pre- 

 cipitates many colloids — as it will precipitate soap. Copper oleate 

 is a soap and is probably soluble to a small degree as such in fresh 

 water, although not soluble to the same extent in salt water. 



That a binder may hold the copper oleate in the lines and in that 

 way prolong its preservative effect is shown by the copper oleate and 

 tar combinations. The remedy indicated for the shortcoming of 

 copper oleate in fresh water may be found in the use of a binder that 

 will keep the copper oleate present and not greatly increase stiffness 

 and weight. Experiments in this field are planned for the near future. 



FLEXIBILITY. 



The flexibility of the cotton lines exposed at Put in Bay was 

 tested in the way previously described (p. 20), both Ijefore and after 

 exposure. The results are given in Table 18 and are shown 

 graphically in Figure 26. 



Table 18. — Flexibility of cotton lines exposed in fresh water at Put in Bay, Ohio.^ 



Symbol and treatment. 



Un ex- 



Number of months exposed. 



Number of oscillations. 



A — Wliite line, imtreated control 



L — Dutch method 



Q— Copper paint No. 1 



R— Copper paint No. 2 



X — Petroleum product No. 2 



Y — Copper oleate, 15 per cent; benzol, 35 per cent; coal tar, 



50 per cent 



Z — Coi)pcr oleate followed by coal tar 



AA — Copper oleate, 15 per cent, in benzol 



41.3 

 44.9 

 3L1 

 29.4 

 34.3 



27.0 

 35. 3 

 43.1 



62.7 

 52.5 

 34.1 

 16.3 

 24.2 



30.0 

 30.5 

 69.7 



69.1 

 51.4 

 38. 7 

 22.1 

 37.3 



31.1 

 34.1 

 74.0 



(2) 

 53.3 

 39.5 

 2L3 



(2) 



2S.4 

 49. 7 

 73.5 



(2) 



.58. 7 

 44.2 

 30.1 

 0) 



34.2 



49.2 



78. 3 



67.1 

 45. 

 37.4 



{') 



52. A 

 40.5 



59.2 

 4(5. 8 

 37.3 



54.2 

 58.0 



1 Every figure in this table is the average of 100 tests. 



2 Line was disintegrated and gone. 



