The Hydrogen-ion Concentration, etc., of Sea-Water. 59 



The following description applies to the 50 c.c. apparatus without the 

 absorption pipette. We would recommend the substitution of a simple 

 2-way stopcock for the one at the top. 



The apparatus was clamped upright to a vertical iron rod rising 6 

 feet from the floor, and a horizontal rod was placed under the lower 

 stopcock to prevent it slipping out of the clamp. The ordinary clamps 

 used in chemistry were used, and the vertical rod supported in the 

 middle by attaching it to the edge of a table with a staple, and at the 

 bottom by inserting it into a hole in a board nailed to the floor. A 

 leveling bulb with cylindrical sides was attached by means of soft- 

 rubber suction tubing (1 mm. bore and 800 mm. long) to the lower 

 end of the apparatus. The leveling bulb was attached by means of a 

 swivel to a screw (of about 6 mm. pitch) and passing through a nut 

 held in a burette clamp on the rod. Another burette clamp was 

 attached to the rod about 800 mm. lower down, and the nut could be 

 changed from one clamp to the other in a few seconds. The stopcocks 

 were greased with a mixture made by dissolving pure gum-rubber 

 (containing no sulphur) in boiling paraffin, and thinning with vaseline. 

 This preparation was satisfactory at 10 and at 20, but a more satis- 

 factory preparation at 30 may be prepared from sapota-tree sap. 



The apparatus was completely filled with mercury and exhausted 

 once by closing the upper stopcock and lowering the leveling bulb, in 

 order to practically free it from air. The bulb was raised again and the 

 air-bubble forced out of the top. The mercury in the cup C was 

 allowed to run down until it filled only the capillary neck. The leveling 

 bulb was lowered below B and 10 c.c. of sea-water were allowed to run 

 quickly from the tonometer electrode into the cup C, and then quickly 

 into the burette B, care being taken that the capillary neck of C 

 remained full of sea-water. 1 c.c. of 2 n HC1 (i. e., acid with about the 

 same absorption coefficient for the elementary gases as the average 

 sea-water) was introduced into C and allowed to run down into B. 

 A little mercury was placed in C and some of it was allowed to run 

 down into B, so that the hole in the stopcock was filled with it and 

 closed. If the stopcock had two holes, as in the figure, the other hole 

 and connecting tube had already been filled with mercury in filling the 

 apparatus with mercury. This mercury effectively sealed the middle of 

 the stopcock, and it seldom leaked, especially if more grease was 

 smeared over the two ends of the stopcock. The stopcocks were 

 usually greased again for each determination. Air getting in at first 

 makes no theoretical difference, but leakage may ruin the determina- 

 tion by occurring at the last. 



By lowering the leveling bulb, the mercury meniscus was brought to 

 the 50 c.c. mark (100 c.c. in fig. 21). The lower cock was closed and 

 the apparatus removed from the clamp and held with the left hand at 

 the attachment of the rubber tube and the right hand at the upper tip 



