234 



BULLETIN OF THE BUREAU OP FISHERIES 



aluminum sulphate, barium sulphate, sodium silicate, sodium chloride, hexamethy- 

 lenamiue, and copper sulphate. Many of them showed heavy fouling in less than 

 150 days, although a few, especially the mercury and copper oxides, showed less 

 than the other materials tested. In a tentative report regarding these results 

 Captain Williams (memorandum, July 25, 1923) stated that "of all the different 

 substances tried the most effective are mercuric and cuprous oxides." 



The American Society for Testing Materials has appointed a subcommittee 

 (No. 23) for investigating antifouling paints. Five annual reports have been sub- 

 mitted, which include the results of many experiments with submerged panels and 

 some tests on ships' bottoms. One definite result that they record is that "differences 

 in fouling and corrosion are as appreciable in underwater paints by varying the 

 vehicle as they are by varying the pigment." This fact would indicate the relatively 

 minor effect of the toxic agents and the major importance of the condition of the 

 paint film. Their final recommendations to date indicate a conclusion only in regard 

 to the toxic compounds to be employed. They recommend as follows: 



Antifouling paints shall contain, in each gallon of paint, copper and mercury in not less than 

 the following amounts for varying service of ship: 



Service 



General 



North Temperate waters. 

 South Temperate waters. 

 Tropical waters 



The compounds of the metals are not specified, excepting that they "shall be 

 present in the form of compounds which are not soluble in distilled water at 20° C. 

 to a greater extent than 1 part per 15,000 parts of water, by weight (0.067 per cent = 

 0.00067)." 



Effect of poison on larval barnacles. — Bray (1923) has studied the effect of various 

 poisons in differing concentrations on the first larval stages of one of the barnacles 

 that causes fouling (Balanus eburneus). He collected large numbers of the newly 

 hatched nauplii and tested their resistance to known dilutions of many supposedly 

 poisonous substances. The actions of the nauplii were carefully noted under a 

 microscope, and the time taken to bring about complete cessation of movement was 

 considered to be the amount of time necessary for the given solution to exhibit its 

 toxic effects. In Table 7 the results of some of his experiments are shown. The 

 author states that these data may be "interpreted very diversely, according to the 

 particular conception one has of the fouling process and the time and manner of the 

 action of the toxic agent or the anticorrosive film. " While virtually all were effective 

 at saturation, this was not the case for such compounds as cobaltous oxide and car- 

 bonate, both of which are fairly soluble in sea water, or for such compounds as anti- 

 mony trioxide and copper carbonate, which are almost insoluble. "Some are very 

 effective at high concentrations but rapidly lose their toxicity on dilution — e. g., 

 arsenious pentasulphide and calcium fluoride." Others, though but slightly soluble, 

 " seem effective at a great dilution — e. g., copper cyanide, mercury arsenate, phenyl 

 arsenious oxide; and especially worthy of note is clorvinyl-arsenious oxide." 



