The firsto a relatively simple series designed to determine 

 whether the charcoal-purifiedp "fat-free" attractant was adsorbed on 

 ion exchamge resm columns^ is illustrated in figure 9o An alcohol e3E= 

 tract of skipjack flesh was passed through a column of activated 

 charcoal; the filtrate was evaporated to dryness -ind extracted with 

 petroleum ether and the residue was dissolved m alcohol and divided 

 into two portiox.So One portion was passed through ol Duolite C = 3 

 cation exchange resin column and the filtrate collected and tested 

 (Noo 178|; the column was then eluted with 5<=percent sulphuric acid 

 and the eluate was collected and tested |Noo ISljo The other portion 

 was passed through a Duolite A<=3 anion exchange resin column, and 

 the filtrate wa.s collected and tested »NOo 179); the column was then 

 eluted with 5«percent soditon hydroxide and the eluate was collected 

 and tested (Noo 182'jo In this particular aeries all tests were positives 

 but the eluate from the anion column {Noe, 182j) appeared to give the 

 strongest responsca 



The above results indicated that a further investigation of 

 the adsorption on an anion colunnn would be profitable^ particularly to 

 see (a) if complete adsorption of the attra^ctant could be attained, (b) 

 to see if the adsorbed material waa completely removed by a water 

 eludte, or if additional adsorbed material could be recovered with 

 either a weak base or a weak acid and Ic) to examine the solubility of 

 the attractant in absolute alcoholo The series is illustrated in figure 

 lOo A clear alcohol extract of tuna flesh was treated with lead 

 acetate to remove proteinSp filteredj and the filtrate was extracted 

 with petroleum ether; it was then treated with hydrogen sulphide gas to 

 precipitate the lead and excess gas was removed in vacuunio The fil- 

 trate was passed twice through a Duolite A->3 anion exchange resin 

 column and the filtrate collected and tested (No,, 200)o The column was 

 then eluteds first with water, next with a weak acid, and finally with 

 a weak bases The water eluate was evaporated to dryness and dissolved 

 in absolute alcohol {No», 201); the residue w^s dissolved in water (NOb 

 20Z)a The base eluate was similarly treated, giving an alcohol soluble 

 portion (Noc 204; and an alcohol-insoluble!, water-soluble portion 

 (NOo 205)o A positive response was obtained only with the alcohol 

 soluble por'ion of the water eluatCo In this series it appears that com- 

 plete separation of the attractant was achieved by use of the anion ex=. 

 change column and that the adsorbed attractant was completely removed 

 by the water eluate a 



In these and other expetiments conducted during the autumn, 

 it appeared that the attractant, purified to a varying extent, was not 

 adsorbed on a cation exchange column^ for positive responses were 

 obtained with the filtrate (No&o 142^ 178, 216;, 225 > rather than the 

 eluateo Only two tests were performed with the latter, however, one 



43 



