Hj'drographical Observations from the Danmark Expedition. 305 



As Knudsen's hydrographical tables were used , the last-men- 

 tioned reading on the burette must be almost equal to the chlorine 

 contents of the normal water (19"39), and this was obtained by giv- 

 ing the solution of silver nitrate a suitable concentration. 



The investigations were carried out in my berth and the arran- 

 gement was as shown in fig. 7. 



The apparatus used for the titrations consisted of the following : 



6 kg. silver nitrate divided into portions of 250 gm. each. 



Two 8 litre bottles of coloured glass with glass-stopper. * 



4 carboys of distilled water. 



Measuring glasses of 1000 gm., 500 gm. and 200 gm. 



Measuring vessel. 



Bent glass-tube and rubber stopper. 



Glass-tube ca. Г/гШ- long, opening ca. 3mm. 



3 m. rubber tubing. 



3 clips. 



Tap lubricant (wax and grease). 



2 rubber pipettes. 



500 gm. glycerine (for pipettes). 



1 burette tripod (50 cm.). 



Water-glass and glass spatulas. 



1/2 kg. neutral potassium Chromate, with pipette. 



1 areometer (35 x 5 cm.). 



1 „ (25 X 9cm.). 

 Filter paper. 



2 glazed clay jars (waste water). 



1/2 kg. potassium hydrate (cleaning). 

 Pure concentrated sulphuric acid (cleaning). 

 1 areometric apparatus. 



25 tubes of normal water (from the Central Laboratory in Chri- 

 stiania). 



3 burettes (2 spherical, with 2 cc. divisions from 16 to 24, and 1 

 with 1 cm. divisions from — 20). 



The first titrations were made on 19. — 22. December 1906 (of 

 the Series I — X), and may be considered to be very reliable, as con- 

 trol determinations with normal water were made for each series. 



In January 1907, however, a snowstorm led to the freezing of 

 most of the normal water, which had been placed in the clock-case 

 in the mess at the place believed to be the warmest in the ship. 

 But even here the temperature became negative. Most fortunately, 

 I had placed a tube of normal water under the mattress in my cabin 

 and here it did not freeze. 



As normal water for the later investigations I used, in addition 

 to this tube, the samples from the deeper layers of the Atlantic, the 

 Х1Л. 20 



