40 



overdragne, til Undersøgelser over Saltgehalten udelukkende 

 anvendt Egerivægtsbéstemmelser, hvorimod jeg paa de to 

 sidste Togter ved Siden af disse ogsaa har udført et. større 

 A ntal Chlortitreringer for gjennem denne Control at sive 

 Resultaterne en større Sikkerhed. 



Til Undersøgelser over den i Søvandet indelioldte 

 Chlormængde medhavdes .paa de to sidste Togter foruden 

 Sølvopløsning af saadan Styrke, at 1 CC. af denne omtrent 

 svarede til 1 CC. Søvand, ogsaa 2 paa første Togt hul- 

 samlede Vandprøver, bestemte til som Normaler at tjene 

 til den nøjagtigere Fastsættelse af Sølvopløsningens Styrke. 

 Disse Normalers Chlormængde i Procenter blev ved om- 

 hyggeligt udførte Veiningsanalyser hvert Aar bestemt saavel 

 før Expeditionens Udreise som eiter dens Hjemkomst be- 

 standig med meget nær det samme Resultat, hvorhos tillige 

 deres Egenvægter ved Hjælp af Aræometret ombord af- 

 læstes. Til Brug ved alle ombord udførte Chlortitreringer 

 tjente kun to Biiretter af lignende Construction og Stør- 

 relse, de samme, som af Stipendiat A. Helland anvendtes 

 ved de Bestemmelser af Chlormængderne i Overfladevandet 

 i Atlanterhavet, som denne foretog i Aaret 1 875 paa en 

 Reise til Grønland, de bleve af ham den Gang calibrerede 

 ved Hjælp af Kviksølv og befundne særdeles tjenlige for 

 Øiemedet. 



Ved Biiretternes Brug fyldtes den ene med Sølvop- 

 løsning den anden med det til Undersøgelse bestemte Sø- 

 vand. hvoretter en passende Portion Søvand fra den ene 

 under Omrystning tilsattes Sølvopløsning fra den anden, 

 indtil al Chlor var udfældt, idet chromsurt Kali tjente som 

 Index.. Begge Bilretters Stand aflæstes nu, og nogle Draa- 

 ber Søvand tilsattes atter til Aflarvning. hvorefter paany 

 fulgte Tilsætning af Sølvopløsning og Aflæsning af Biiret- 

 ternes Stand o. s. v. GJ ennem en Række af 4 a 5 paa 

 hiiWiden følgende lignende Aflæsninger erholdtes paa denne 

 Maade de fornødne Data til Beregning af det Volum Sø- 

 vand. som i hvert enkelt Tilfælde svarede til 1 CC. Sølv- 

 opløsning. 



Paa denne Maade sammenliknedes paa den ene Side 

 Søvandsprøyerne og paa den anden Side ogsaa fra Tid til 

 anden de medbragte Normaler med Sølvopløsningen, idet 

 der altid sørgedes for, at Vandprøvernes og Opløsningernes 

 Temperatur ikke fjernede sig synderlig meget fra hinanden, 

 Biiretterne bleve for at tilveiebringe en bedst mulig Aflob- 

 ning hyppig lensede med eoncentreret Svovlsyre. 



Af de gjennem disse Observationer erholdte Tal er 

 senere Søvandets Chlormængde beregnet elter følgende 

 Formel 



1> - 



k s r 



I: $ 



hvori /i betegner den undersøgte Vandprøves Chlormængde 

 i Procenter, /,' det Anta] CC. af samme, der svare til 1 



('('. Solvoplosning og x' dens Kgenvægt ved 17.°5 C, P 

 Middeltallet niellem de for Vdreisen og efter Bjemkomsten 

 i Normalen firadne Chlormængder, K det Antal CC. som 

 af denne svarer til ICC. Solvoplosning og S dens Fgeu- 



work, made exclusive use of specihc gra v i ty determinations: 

 but for a considerable number of my own observations, on 

 the last two cruises. I also adopted titra tion for chlorine 

 as a means of testing the general accuracy of the results. 



For estimating the amount of chlorine in sea-water. 

 I took vvitli me. on the two last cruises, besides a solution 

 of silver of such strength that 1 cc of the fluid about corre- 

 sponded to 1 cc of sea-water, also 2 samples of water col- 

 lected on the first voyage. to serve as a normal standard 

 by which to determine the Strength of the solution of 

 silver. Each year. hoth previous to the depårture of the 

 Expedition and after its return. the chlorine in these 

 standard samples was carefully determined by weighing, and 

 the percentage calculated accordingly, their specific gravity 

 too. as shown by the areometer on board, ha ving been like- 

 wise noted down. For all chlorine-titrations performed at 

 sea. there were only two burettes in use. similar alike in size 

 and construction. --- those used by Mr. Helland for determ- 

 ining the amount of chlorine in the surface-water of the 

 Atlantic on a voyage to Greenland in 1875; he had cali- 

 brated them by means of mercury, and they proved excel- 

 lently adapted for the purpose. 



When using the burettes. one was filled with solution 

 of silver and the other with the sea-water selected for 

 examination, after which solution o"f silver was added to a 

 proper quantity of the sea-water. while shaking the flask 

 in' which the titration was performed till all chlorine had 

 been precipitated, chromate of potassium serving as the 

 index. The height of the fluid in both burettes was now 

 read. and a fe w drops of sea-water added to the mix- 

 ture, to discolour it. after which solution of silver was aga in 

 added. and the height of the fluids read as before, &c. 

 A iler the height had been tims read 4 or 5 times in 

 succession, the necessary data were obtained for computing 

 the volume of sea-water. which in each individual case cor- 

 responded to 1 " solution of silver. 



In tliis manner, were compared on the one hand the 

 freshly drawn samples of sea-water. and on the other. from 

 time to time, also the standard samples, with the solution. 

 of silver, care being tåken to keep the samples of water 

 and the solution as near as possible at the sann' tempera- 

 ture. In order to prevent any portion of the fluid from 

 adhering to the burettes, they were frequently rinsed with 

 concentrated sulphuric acid. 



With the figures obtained from these observations. the 

 amount of chlorine in sea-water was afterwards determined 

 by the following formula - 



KSP ' • 

 >'= /,, 

 in which )> signities the percentage of chlorine in the 

 sample of water examined, Je the proportion in cubic cen- 

 timetres representing 1 " of the solution of silver. and 

 x the speeilie gravity of the water at 17" 5 C; Pthemean 

 lielween tlie auioiints of chlorine found ill the standard 

 sample before the depårture and alter the return of the 



