REPORT ON THE COMPOSITION OF OCEAN-WATER. 
141 
proportions of nitrogen and oxygen in the samples of sea-water on board the ship, wisely 
contented himself there with merely extracting the gases from the recently drawn 
samples, and then sealing them up in glass tubes for subsequent analysis at his leisure 
on terra firma , in a properly appointed laboratory. 
Jacobsen's Method of Extracting Gases from Sea-Water. 
The method which Jacobsen used for the extraction of the gases, as will be seen by 
the following description, was a modification of the one 
invented long ago by Bunsen, and described in his 
Gasometrische Methoden. A round-bottomed flask of 
500 to 1000 c.c. capacity is provided with a well-fitting 
soft vulcanised india-rubber stopper, pierced with one 
perforation. This aperture serves for the attachment 
of the gas-collecting apparatus as shown by the 
adjoining figure. 
The tube which forms the lower end of this 
apparatus is closed at the bottom, but has a small 
aperture at the side. The upper (exit) end of the 
apparatus is provided with a well-fitting narrow india- 
rubber tube and a screw-clip, so that it can be closed 
hermetically when required. In the execution of the 
process the first step is to fill the flask to overflowing 
with the water to be examined by means of a wide and 
long-necked funnel,* which goes to the bottom of the 
flask, water being poured in in a continuous stream, 
unbroken by drawn-in air-bells, until some 100 or 200 
c.c. of water have run over the edge of the flask, so as 
to make sure of the contents being unaffected by 
absorptiometric exchange with the atmosphere. On 
the other hand, the lower pear-shaped bulb a of the 
gas-collector is charged with a small quantity of 
pure water, the india-rubber stopper inserted in the 
flask, and the lower (laterally perforated) end of the 
bulb a pushed down the hole about one-half or two- 
thirds of the way, so that the flask is hermetically 
Fig. 3. — Jacobsen’s Apparatus for the Extraction 
of Water-Gases. 
shut off from communication with the interior of the gas-bulbs. 
The air contained in the 
* In the case of a deep-sea water which has been hauled up by means of a pipette-shaped bottle like the one used 
in the Challenger Expedition, a wide india-rubber tube is attached to the lower end ol the “ bottle,’' and, by means of 
it, the water led to the bottom of the boiling-out flask. 
