25 
derfor Temperaturen steg over 100°. undveg altsaa altid 
vel maalelige og ofte endog temmelig betydelige Mængder 
Kulsyre. 
Ved de påa Pomeraniaexpeditionen i 1871 udførte 
Lufthestemmelser *, hvor den tidligere beskrevne Methode 
med Gasarternes Udkogning under et, ved Vanddamp frem- 
bragt \ acuum anvendtes. sænkedes imidlertid Temperaturen 
ikke ubetydeligt, og det viste sig da. at man ved denne 
Temperatur temmelig ofte kun fik næsten umaalelig smau 
Qvantiteter Kulsyre uddrevet sammen med den øvrige Luft. 
medens de tidligere Uoverensstemmelser mellem flere med 
samme Vandprøve. gjentagne Udkogninger ogsaa lier gik igjen. 
Jacobsen fandt sig derfor ved dette mærkelige Phæ- 
nomen foranlediget til nærmere at andersøgé Kulsyrens 
Absorbtionsforhold ligeoverfor Søvand. 
Gjennem de Forsøg, som han i denne Anledning an- 
stillede, wiste det sig da. at man ad andre Veie kunde 
paavise aldeles uventet store Qvantiteter Kulsyre i det 
samme Vand. hvoraf man ved en i flere Timer fortsat Ud- 
kogning efter Bunsens Methode kun kunde erholde meget 
smaa Mængder. Åfdestilleredes nemlig Søyandet i en kul- 
eyrefri Luftstrøm uden Luftfortynding i en Retorte, undveg 
der den hele Tid Kulsyre. lige indtil den hele Mængde 
Vædske var afdestilleret. saaledes at man først ved rigelig 
Udskillelse af Salte kunde være fuldstændig sikker paa at 
have erholdt det samlede Udbytte af Kulsyre uddrevet. 
Der lod sig under Udkogningen ikke paavise noget 
Punct. hvor man kunde tale om en Grændse mellem fri 
og surt hunden Kulsyre. 
Paa denne Maade uddrev nu Jacobsen ved fuldstæn- 
dig Afdestillation af 1 j 4i Litre Søvand i en kulsyrefri Luft- 
strøm den hele Mængde Kulsyre og opsamlede den efter 
Pettenkoffers Princip i en afmaalt Mængde titreret Baryt- 
vand, som efter endt Operation retitreredes med Oxalsyre, 
og beregnedes efter disse den samlede Kulsyremængde, som 
for ufortyndet Nordsøvand opgives til omkring 100 Mgr. 
per Litre. 
Samtidig bestemtes ogsaa i Residuet fra Inddampning 
a/ circa ID Litre af det samme Vand den i de neutrale 
Carbonater indelioldte Kulsyre til i Middel kun omkring 
10 Mgr. per Litre. 
Ifølge disse Observationer kunde altsaa kun en meget 
liden Brøkdel af den ved Destillationen uddrevne Kulsyre 
betragtes som surt hunden, og Jacobsen imødegaar derfor i 
sin Afhandling bestemt den af Vierthaler 2 gjorte Antagelse, 
at al den ved Kogning afSøvandet uddrevne Kulsyre skulde 
være surt hunden. Han anser sig endvidere aldeles sikker 
for under Inddampningen ikke at have erholdt decomponeret 
nogen Del af de i Søvandét iudeholdte neutrale Carbonater, 
idet hau udtrykkelig siger: ‘*Die ganze Menge der nicht 
1 Ann. Chem. Pharm. 167 — 1. 
8 Wien. Acad. Ber. [2] — 56 — 479. 
Den norske Nordhavsexpedition. Tornoe: Cheim. 
ing-process was conducted with lull atmospheric pressure, 
or at a temperature of more than 100° C., invariably proved 
appreciable, nay sometimes rather large. 
When performing the air-determinations 1 on the ‘Pom- 
erania’ Expedition in 1871 (by the method, previously 
described, of boiling out the gaseous elements in a vacuum 
created by steam), the temperature kept considerably lower, 
and the quantity of carbonic acid expelled with the other 
atmospheric element» at a comparatively low temperature 
was often immeasurably small : moreover, the variable char- 
acter of the results, alluded to above, on repeating the 
boiling-process with the same sample of water again as- 
serted itself. 
Struck by this remarkable phenomenon, Jacobsen 
determined to investigate anew the absorptive capacity of 
sea-water in relation to carbonic acid. 
The experiments of that chemist undertaken with the 
above ebject in view afforded conclusive proof of the fact, 
that large quantities ol carbonic acid were still present in 
water from which a very small amount only could be ex- 
pelled after several hours’ protracted boiling by Bunsen’s 
method. On distilling in a retort sorb-water exposed to a 
current of air free from carbonic acid, but not varified. 
carbonic acid is found to escape so long as any portion 
ol the fluid remains undistilled, an abundance of solid 
deposit however being the only indication that all or nearly 
all the carbonic acid present in the water has been driven off. 
During the process of boiling no particular moment 
could be determined marking the escape of the carbonic 
acid present as gas and of that which has combined with 
carbonates to form bicarbonates. 
In this manner, by distillation in a current of air 
free from carbonic acid, .Jacobsen succeeded in expelling 
the whole amount of carbonic acid contained in ‘/i litre 
of sea-water, and collected it, by Pettenkoffer's method, in 
a given quantity of titrated baryta water of known strength, 
which, on the operation being terminated, he retitrated 
with oxalic acid, computing accordingly the total amount of 
carbonic acid driven off in the process. Undiluted North 
Sea water contains according to Jacobsen’s results about 
100^ r per litre. 
The amount of carbonic acid contained by the neutral * 
carbonates in the residuary deposit from the evaporation 
of 10 litres of the [same water, was also calculated, and 
found to average only about 10 m < ?r per litre. 
According to these observations, a very small propor- 
tion only of the carbonic acid driven off by distillation 
could have been present in bicarbonates ; and hence Ja- 
cobsen emphatically opposes Vierthaler’s assumption, 2 that 
the carbonic acid boiled out of sea-water occurs in that 
form. Moreover, he feels quite sure that no portion of 
the neutral carbonates in the water examined was de- 
composed during the process of boiling. "Die ganze Menge." 
he says, i( der nicht mit Basen zu neutralen Salzen verbun- 
1 Ann. Chem. Pharm. 167, p. 1. 
8 Wien. Acad. Bcr. [2] 50, p. 479. 
4 
