54 



Papers from the Department of Marine Biology. 



leveling bulb was lowered and the lower stopcock of the separatory 

 funnel was opened cautiously. When the required amount of CO2 was 

 admitted, the lower cock was closed, the 3-way cock reversed, and the H2 

 apparatus substituted. The CO2 was washed out of the connections and 

 the 3-way stopcock turned as in figure 17 and H2 admitted by opening 

 the lower stopcock. The operator kept his hand on this stopcock until 

 the filling was complete, because the H2 came faster at first than later, 

 and there was danger of the mercury leaving the separatory funnel 

 faster than the H2 was suppUed, in which case water would be sucked 

 in from the trap 0. It was necessary to allow a little H2 to escape 

 continuously through the trap 0, as a matter of safety. When the 



Fig. 18. — Hydrogen electrode for determining the Ph of water taken directly 

 from the sea. A drop of water is placed in the trap t, to seal it, and the 

 electrode is filled with pure hydrogen. The hole in the 3-way cock is filled 

 with sea-water by sucking on a rubber tube attached to b while a is 

 immersed in the water; then this cock is reversed and the suction applied 

 at t until the sea-water rises to the mark m, when all cocks are 

 closed. The 1.5 c.c. of hydrogen remaining in the electrode is shaken 

 with the 10 c.c. of sea-water in the large compartment until it has the 

 same CO2 tension as the sea-water, when it is passed into the small 

 compartment by opening the large cock c (which must be 4 mm. bore 

 and not greased) and tapping the electrode. D is opened a moment 

 before c is closed to reestablish atmospheric pressure and the electrode 

 is shaken again before taking the reading. Electrolytic connection is 

 made through the ungreased cock c. A wire is hooked in p to connect 

 with the potentiometer. 



mercury meniscus reached the lower mark, the cocks were closed and 

 the apparatus shaken, the remaining mercury stirring and mixing the 

 gas. The tonometer electrode was now attached, the leveling bulb 

 was raised, and the gas mixture was passed through the tall column of 

 sea-water in fine bubbles, which was accomplished only after a careful 

 adjustment of all the stopcocks. 



For the detemiination of the Pg of sea-water taken directly from the 

 sea, the electrode shown in figure 18 was used. It was first filled with 

 H2 and then sea-water was admitted through a to the mark m, after 

 washing out the air at h. The H2 was shaken with 10 c.c. of sea-water 

 in the large compartment; then by tapping the apparatus it was caused 

 to enter the smaller compartment and again shaken. In this way the 

 loss of CO2 by the second portion of sea-water was minimized. The 



