80 OTTO GLASER. 



in three closely concordant experiments that 36.9 per cent, of the 

 copper had been precipitated in the sea-water — in all probability — 

 as insoluble basic carbonates. The sea-water, therefore, retained 

 in solution a trifle over .174 mg. Cu per c.c. — the equivalent of 



Cu = m/2,6$ or w/730. 



III. The Removal of Copper from Solution by Normal 



Eggs. 



The precipitated fraction of the copper sulphate interferes seri- 

 ously with attempts to measure colorimetrically the quantities actu- 

 ally removed by the eggs. Not only is the turbidity of the solution 

 objectionable, but the precipitate adheres mechanically to the cho- 

 rion, which in turn goes slowly into solution. It is absolutely 

 essential to eliminate the copper carbonates. 



However, a concentration of w/730, even after the carbonates 



are removed, often destroys the eggs in all except brief exposures. 



This difficulty can be overcome by dilution to n/ 1,460. At this 



concentration .2 c.c. of dry ripe eggs in 75 minutes reduced the 



copper content of 14.8 c.c. of solution as follows: 



Lot A from w/ 1,460 to m/i, 810.4. 



Lot B from n/ 1,460 to n/i, 766.6. 



Lot C from w/1,460 to n/i ,785.5. ' 



Very definitely, then, Arbacia eggs are able to remove copper 

 from solution, yet, despite their close agreement, the figures in 

 reality have no quantitative standing. They completely mask an 

 important source of error. 



IV. The Role of the Chorion. 

 If the chorion takes part in lowering the concentration of copper 

 solutions, eggs without jelly should lose at least part of their 

 effectiveness. But to demonstrate this is not easy. The very re- 

 moval of the chorion, of itself, introduces variables which, in the 

 present case at least, might be increased in number or aggravated 

 by the use of dilute hydrochloric acid as a solvent of the jelly. 

 This restricts us to the mechanical methods with their relative 

 violence and uncertainty. One can never feel confident that every 

 egg has lost its chorion, nor that the shaking, flipping— or whatever 

 one does — leaves every egg intact. Some control of these errors 



