140 FRIDTJOF NANSEN. 



The amount of halogen in all the small water-samples of 100 

 ccm. has been determined by Mr. Helland-Hansen by titration. 

 He has attained a high degree of accuracy in his determinations 

 by constantly checking his results, for every tenth observation, 

 by comparisons with tests on standard water recieved from Mr. 

 Knudsen in Copenhagen. By repeating his determinations on 

 series of the same samples Mr. Helland-Hansen found that the 

 average difference in his results did not exceed 0.018 ^/o in sali- 

 nity of the water. When the water-samples have stood for 

 some time in these small bottles with cork-stoppers, however it 

 seems as if they more or less change their salinity (see later). 



The larger water-samples of 500 ccm. have all been exa- 

 mined by my assistant Mr. Jacob Schetelig with my hydrome- 

 ters of total immersion^ and their specific gravity (S j^tt) has 



been determined with an accuracy of the unit in the fifth deci- 

 mal place. By repeating the determinations of the same water- 

 samples at intervals of several months we have as a rule found 

 no difference in the results, if no mistakes had been made. For 

 the sake of convenience, the determinations have been referred 



17'5*^ G 

 to S . „^p^Q ' by Makaroff's tables. For the final report Knud- 



1 I'D Vj. 



sens new Tables will be used, when they appear. As the changes 

 of the volume of sea-water by various temperatures have not 

 hitherto been known with sufficient accuracy, and as the correct 

 factors for reducing specific gravity and permillage of halogen 



See, Nansen, The Norwegian North Polar Expedition, etc., vol. III. 

 No. X. An hydrometer of Jena Glass No. 16 III with a volume of 

 118 ccm. made hy Küchler of Ilmenau, vpas used for daily work. This 

 instrument had a specific gravity of 1.0215 at 17.5° C. Its constants 

 had been determined by myself in May, 1900. For control tests four 

 hydrometers of Jena Glass No. 59 III made by Richter (Berlin) have 

 been used. These excellent instruments have volumes about 66 ccm. 

 and their specific gravities are about 1.0000 at 17.5° C. Their absolute 

 weight and volume have been determined with a high degree of accu- 

 racy at the Reichsanstalt, at Charlottenburg. 



