HYDROGRAFI. 2 - 



with the areometer that had been used. The glass in which the determination took place, was hung 

 up after the Cardano system in the laboratory. The temperature appertaining to the areometer-readings 

 was determined by two thermometers divided into tenths of degrees. Like the areometer, the same two 

 thermometers were used during all the measurings. The bulb of one of them was placed right under 

 the surface of the water, and that of the other near the bottom to enable me to be on the safe side 

 against too great inequalities in the temperature of the water. During the first voyage, determination 

 of the specific gravity was made with all the samples of which the amount of chlorine likewise had 

 been determined, while, on the other hand, it was not made in 1896 with those samples from the 

 depth that were brought home. The measurings with the areometer were attended with a great deal 

 of difficulty, on account of the vibration caused by the engines and the propeller of the vessel, so 

 that these measurings have only been effected to serve as a guard against great titrational errors, as 

 the salinity was determined by the specific gravity, by multiplying the cipher obtained by reduction 

 after KrilmmcVs table («Ueber den Gebrauch des Araometers an Bord» pag. 13) by 1310. The deter- 

 minations of the salinity obtained in this manner, cannot, in so far as correctness 

 is concerned, be compared to those obtained by the chlorine-titrations, and they 

 have not for this reason been put down in the tables. 



DETERMINATION OF THE CHLORINE. 



Owing to the great development of oceanographic investigations of late years, the determina- 

 tion of chlorine has become a matter of the greatest importance, and titration of the chlorine 

 has therefore been made with almost all the samples of water of which the tem- 

 perature was determined. 



Notwithstanding the fact that a titration of chlorine in itself is a very easy matter, we must, 

 in consequence of the many determinations, which are to be executed with the greatest exactness, 

 have a regular method of working. Concerning this latter and the fitting up of my laboratory, I 

 have obtained many valuable hints from Dr. H. Topsoe, who always assisted me by word and deed, 

 when I was at a loss how to act. 



To determine the quantity of chlorine, I used the system of volume titration: precipitation with 

 a solution of silver-nitrate, and the application of chromate of potash as index. As the vessel on the 

 voyages had on board weighed off quantities of silver-nitrate in crystals placed in hermetically sealed 

 glass-tubes, as well as distilled water in balloons, the solution of silver-nitrate could take place on 

 board ship. The contents of one glass-tube were dissolved in 1 litre of water, and solutions of this 

 kind would then be nearly of equal strength. This latter was determined exactly by titration of sea- 

 water, the quantity of halogens of which was ascertained exactly beforehand, and found to be 

 suitable when a solution of 35 c - cm - of silver-nitrate was required to neutralise the halogens in 25 c - cm - of 

 ocean-water. Frequently and at least three times during the use of 1 litre of the solution, the strength 

 was determined, and besides many samples of water were taken home for further testings after the 

 expedition had come to an end. 



The titration was then effected as follows: z$ c - cm - of sea-water were measured off by a pipette 



4* 



