overdrawn*, til Undersøgelser- over Saltgehalten udelukkende 
anvendt Egenvægtsbesteramelser, hvorimod jeg paa de to 
sidste Togter ved Siden af disse ogsaa har udført et større 
Antal Chlortitreringer for -gjennem denne Control at give . 
Resultaterne en større SikkcrlW- 
Til Undersøgelser over den i Søvandet indeholdte 
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 ind- 
saralede Vandprøver, bestemte til som Normaler at tjene 
til den nøjagtigere Fastsættelse af Sølvopløsningens Styike. 
Disse Normalers Chlormængde i Procenter blev ved om- 
hyggeligt udførte Veiningsanalyser hvert Aar bestemt saavel 
før Expeditionens Udreise som efter dens Hjemkomst be- 
standig med meget nær det samme Resultat, hvorhos tillige 
deres Egenvægter ved Hjælp al‘ Aræometret ombord af- 
læstes. Til Brug ved alle ombord udførte Chlortitreringer 
tjente kim 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 1875 paa en 
Reise til Grønland, de bleve af ham den Gang calibrerede 
ved Hjælp af Kviksølv og befundne særdeles tjenlige for. 
Øieraedet. 
Ved Biiretternes' Brug fyldtes den ene med Sølvop- 
losning 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 chrbmsurt Kali tjente som 
Index. Begge Biiretters Stand aflæstes nu, og nogle Draa- 
ber Søvand tilsattes atter til Aftarvning, hvorefter paany 
fulgte Tilsætning af Sølvopløsning og Aflæsning af Biiret- 
ternes Stand o. s. v. Gjennem en Række af 4 a 5 paa 
hina mlen 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 sammenlignedes paa den ene Side 
Søvandsprøverne 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 rensede med concentreret Svovlsyre. 
Af de gjennem disse Observationer erholdte Tal er 
senere Søvandets' Chlormængde beregnet efter følgende 
Formel 
KSP 
3)= u 
hvori p betegner den undersøgte Vandprøves Chlormængde 
i Procentei\ k det Antal CC. af samme, der svare til 1 
CC. Sølvopløsning ♦ og s dens Egenvægt ved 17. 5 C'.. P 
Middeltallet mellem de før Udreisen og efter Hjemkomsten 
i Normalen fundne Chlormængdef, K det Antal CC., som 
af denne svarer til 1 CC. Sølvopløsning og S dens Egen- 
work, made exclusive use of specific gravity determinations; 
but for a considerable number of my own observations, on 
the last two cruises, I also adopted titration for chlorine 
as a means of testing the general accuracy of the results. 
For estimating the amount of chlorine in sea-water, 
I took with me. on the two last cruises, besides a solution 
of silver of such strength that 1 ec of the fluid about corre- 
sponded to 1“ 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, both previous to the departure 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, having 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 of 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 few drops of sea-water added to the mix- 
ture. to discolour it, after which solution of silver was again 
added, and the height of the fluids read as before, &c. 
After the height had been thus 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' this 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 taken to keep the samples of water 
and the solution as near as possible at the same 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 
v - ~ i- ir 
in which p signifies the percentage of chlorine in the 
sample of water examined, k the proportion in cubic cen- 
timetres representing l ec of the solution of silver, and 
s the specific gravity of the water at 17° 5 C. ; P the mean 
between the amounts of chlorine found in the standard 
sample before the departure and after the return of the 
