32 TJ. S. BUREAU OF FISHERIES. 



ordinary soaps are produced. If, instead of the alkalis, any other 

 metal — such as copper, mercury, aluminum, etc. — is used, insoluble 

 soaps — such as copper soap, mercury soap, aluminum soap, etc. — are 

 produced. The simplest method of preparing these " heavy metal 

 soaps " is first to make ordinary soap, then treat it in solution with 

 a compound of the metal Avhose soap is desired. Thus, if to a solution 

 of ordinary soap aluminum chloride is added, an insoluble waxy 

 precipitate falls — aluminum soap; if copper sulphate is employed 

 instead of aluminum chloride, a bright green, insoluble copper soap 

 is formed. The insoluble calcium soap is a very familiar substance 

 formed when soap is dissolved in " hard " water — a tallowy stull 

 that gets on one's hands, the bathtub, etc. This is calcium or lime 

 soap. A similar soap is used for temporary calking of small leaks in 

 boats ; a soap of aluminum is used to waterproof clothing, for it makes 

 clothes difficult to wet, the water rolling off " like water from a duck's 

 back." 



Now, if the principal reason for using copper to preserve nets is 

 that it kills bacteria and other injurious living things, and if the 

 principal objection to its use as bluestone is that it washes out so 

 readily, there will be no difficulty in seeing that the object of using ii 

 in the form of a soap is to take advantage of its protective property 

 and at the same time to prevent it from escaping into the water. 

 Since copper soap is quite insoluble in water, there would be no way 

 to get it into the fibers if it were made before it is applied ; it is there- 

 fore necessary to cause the copper soap to be produced inside the fiber 

 by impregnating the threads first with soap solution and then with 

 copper sulphate. In the practice of preserving nets the following 

 process, according to Cunningham, is used : 



To treat a net by this process from one-half to three-fourths pound of ordi- 

 nary soap, such as mottled soap * * * is used for each gallon of water, 

 and the soap is dissolved by boiling in a copper or in a galvanized bath over a 

 fire. The net is then soaked in the soap solution, taken out, squeezed through 

 the hands, and allowed to drain. The copper sulphate, which is also known as 

 blue vitriol or bluestone, must not be dissolved in an iron vessel, as it will at- 

 tack and dissolve the iron. It must be put into a wooden or earthenware ves- 

 sel, and it is not necessary to use heat to dissolved it, as it will dissolve in cold 

 water if stirred up for a short time. The net while still hot from the soap 

 solution is then passed through or put into the solution of bluestone, and the 

 whole net becomes uniformly green.' The net is then rinsed in cold water. 

 About three-fourths pound of bluestone to a gallon of water is the proportion 

 required. 



This method preserves the net, according to Cunningham's fig- 

 ures, for about four weeks, but he says that after two months the 

 sample treated was quite rotten. The process can, of course, be re- 

 peated as often as necessary, and by repeated treatments a net should 

 be kept in condition for years. It causes strong shrinking of the net. 



A similar method is recommended for ropes and canvas by the 

 Norsk Fiskeritidende (1887). The procedure there given is as 

 follows : 



Ropes are laid first for four days in a solution of copper vitriol (20 grams 

 to a liter of water — two-thirds ounce to a quart) and then dried. They are then 

 tarred in the usual way or laid in a soap solution (100 grams to a liter of 

 water — 3J ounces to a quart) until they are saturated through. Canvas is 

 treated only with the vitriol and soap. 



