54 IT. S. BUREAU OF I^ISHEKIES. 



The results obtained in all four of the above experiments would 

 seem to indicate that there need be no fear of spontaneous heating 

 of nets treated with copper oleate, either oxidized or unoxidized. 



OTHER PRESERVATIVES. 



Creosote oil: The substance as previously described as being used 

 for a lubricant in the manufacture of copper oleate. 



Heavy coal tar: A road tar diluted with an equal volume of benzol 

 in order to thin it sufficiently for application. 



Pine tar: Ordinary wood tar, thinned with an equal volume of 

 benzol. 



Light coal tar: A thin crude coal tar, containing all the substances 

 found in crude coal tar with the exception of water and benzol. 



Copper paint No. 1 : A copper paint used as a net preservative. 



All of the above products were tested by saturating cotton waste 

 with each and placing it in the tester. In no case was there any 

 evidence of spontaneous heating. The maximum temperature noted 

 at any time m the air smrounding the sample was 203° F. (95° C). 

 Observed fluctuations in the temperature were in all probability due 

 to air currents. At no time was the temperature of the waste over 

 200° F. (93° C). The major portion of the time it was between 190 

 and 197° F. (88 and 92° C). The water in the outer jacket was kept 

 at boiling. 



EFFECT OF HEAT ON COTTON LINES. 



The question may here be raised as to how much heating is neces- 

 sary to cause noticeable deterioration of the line. In order to answer 

 this question, the following experunents were carried out: 



Samples of No. 24 cotton line were heated in an electric oven in 

 dry heat. One sample- was heated for a period of two hours at a 

 temperature of 212° F. (100° C), another for two hours at 257° F. 

 (125° C), and a third for two hours at 302° F. (150° C). These 

 samples were subjected to tests for tensile strength and showed no 

 appreciable weakening due to the heating. The sample that had 

 been heated to 302° F. (150° C.) was slightly browned or scorched 

 in appearance but was fully as strong as any of the other samples. 



Other samples of the same kind of twine were heated in steam. 

 One sample was heated with steam at 212° F. (100° C), another at 

 239° F. (115° C.) under 10 pounds steam pressure, and a third at 

 257° F. (125° C.) under 20 pounds steam pressure. All samples were 

 heated for two hours. Tests of tensile strength were also made on 

 these lines, and again there was no noticeable difference between the 

 lines that had been heated and those that had not. 



The results of these experiments seem to indicate that a tempera- 

 ture much higher than any to which fish nets or lines are ordinarily 

 subjected would have to be reached before any noticeable weakening 

 of the threads would take place from the heat alone. 



DISCUSSION OF RESULTS. 



That some kind of heating occm's in nets in use seems certain. 

 Since it is shown here that even linseed oil must be artificially heated 

 to a comparatively high temperature before it continues to heat 



