Full resolution (JPEG) - On this page / på denna sida - Sidor ...
<< prev. page << föreg. sida << >> nästa sida >> next page >>
Below is the raw OCR text
from the above scanned image.
Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan.
Ser du något fel? Korrekturläs sidan nu!
This page has never been proofread. / Denna sida har aldrig korrekturlästs.
28
Dette syntes ogsaa meget vanskeligt at forklare,
saafremt det virkelig skulde forholde sig som af Enkelte
paastaaet. at der i Søvandet skulde lindes et meget stort
Overskud af fri Kulsyre ved Siden af en meget liden
Qvantitet af sure Carbonater. Det maatte aabenbart synes
meget rimeligere at forklare de af Dr. Jacobsen gjorte
Observationer derved, at Søvandet under den langvarige
Kogning ved en eller anden chemisk Reaction gav Slip paa
noget af sin neutralt bundne Kulsyre.
For at komme paa det Rene med, 0111 dette virkelig
forholdt sig saa, gik jeg frem paa følgende Maade:
200 CC. Søvand (af sp. Vægt 1.0267 ved 17.°5 C. i
Forhold til destilleret Vand af samme Temperatur)
afdestilleredes næsten til Torhed i en kulsyrefri Luftstrøm, og
opfangedes den undvigende Kulsyre i 25 CC. af en
Baryt-opløsning, hvoraf 1* CC. svarede til 4.0204 Mgr. Kulsyre.
Ved Retitration med Oxalsyre viste det sig, at 19.97 CC.
af det anvendte Barytvand var uneutraliseret, hvoraf den
undvegne Kulsyre beregnedes til 20.2 Mgr. Residuet
paa-helcltes nu friskt udkogt Vand, som atter afdestilleredes,
hvorved endnu et ubetydeligt Spor af Kulsyre erholdtes.
Sluttelig tilsattes circa 0.5 Gr. fuldkommen ren friskt
udglødet Soda, hvorpaa det Hele atter fortyndedes med
kulsyrefrit Vand til Søvandets oprindelige Volum og saa
af-destilleredes i en kulsyrefri Luftstrøm.
Allerede fra det Øieblik af, da Vædsken var kommen
i Kog, begyndte strax en saa voldsom Kulsyreudvikling, at
det i Forlaget anbragte Barytvand slåp store Mængder
uabsorberede igjennem, og det viste sig efter endt
Operation. at kun 1.3 CC. Barytvand var forblevet
uneutraliseret. Heraf beregnes den absorberede Del af den undvegne
Kulsyre til 95.3 Mgr., medens desforuden meget betydelige
Mængder gik igjennem, idet nemlig Barytvandet i et
ufor-migt Rør, som var anbragt foran Forlaget, fuldstændigt
var forbrugt.
Efter Forslag af. Professor Waage gjentoges Forsøget
med varmt fældt, ved 100° tørret kulsur Kalk. hvoraf det
ogsaa lykkedes at uddrive ikke ubetydelige om end meget
mindre Mængder Kulsyre, hvorimod der ved et Forsøg
med fint pulveriseret Marmor ikke erholdtes noget sikkert
Resultat.
Betydningen af disse Observationer kunde ikke være
tvivlsom, da det hermed paa det Tydeligste var godtgjort, at
den i Søvandet forhaandenværende Saltblanding ved
Koghede decomponerede neutrale Carbonater, og dermed ogsaa,
at alle de hidindtil gjorte KiUsyrebestemmelser med
Hensyn paa sin Hensigt at bestemme den i Søvandet
indeholdte frie og surt bundne Kulsyre vare forfeilede. Hvad
angaar de før Publicationen af Dr. Jacobsens Afhandling
om Luften i Søvandet udførte Kulsyrebestemmelser, da
eidet en Selvfølge, at de alle uden Undtagelse maatte være
i enhver Henseende fuldstændig værdiløse, idet der ved
dém intetsteds er kommen til Anvendelse en Afdestillation
til Tørhed eller en saa vidtdreven Concentration, at man
This fact would obviously be most difficult of
explanation if, as some have affirmed, sea-water does actually
contain a very large surplus of free carbonic acid along
with an exceedingly small proportion of bicarbonates. A
more plausible hypothesis by which to explain Dr. Jacobsens
observations were surely the assumption, that during the
protracted process of boiling some of the neutral
carbonates present in sea-water had been decomposed.
With the object of ascertaining whether such was
really the case, I went to work as follows.
Two hundred c.centim. of sea-water (sp. grav. 1.0267 f
temp. 17."5 C., as compared with distilled water of the
same temperature) were distilled almost to dryness in a
current of air free from carbonic acid, and the carbonic
acid collected in 25cc of baryta water, lcc of which
represented 4.0204m9-r carbonic acid. On being retitrated
with oxalic acid 19.97cc of the baryta water were found not
to be saturated, and 20.2 carbonic acid had
accordingly been driven off. Water freshly boiled was now poured
on the residue, and then evaporated, the result yielding a
slight trace of carbonic acid; finally, about Ö.5m,jr purified
and freshly heated soda was added, and the whole
compound again diluted with water, from which all carbonic
acid had been expelled, to the original volume of the
sample, and then distilled in a current of air free from
carbonic acid.
From the very moment at which the fluid began to
boil, so rapid was the liberation of carbonic acid that
large quantities passed unabsorbecl through the baryta
water; and, on the operation being terminated, 1.3cc
only of the baryta water had not been neutralised. Hence
the absorbed portion of the carbonic acid was calculated
at 95.3 m♂r, exclusive of which a very considerable quantity,
as before stated, passed off into the atmosphere, the baryta
water, placed in a glass tube (resembling in form the
. letter U) connected with the receiver, being surcharged
with the gas.
At Professor Waage’s suggestion I repeated the
experiment with carbonate of lime, precipitated warm and
dried at a temperature of 100° C., and succeeded in
expelling carbonic acid in considerable, though not so large,
quantities as before, whereas an experiment with finely
pulverised marble gave no positive result.
The importance of these observations was not to be
questioned, affording as they did conclusive proof that the
saline mixture in sea-water, on the temperature being raised
to the boiling point, decomposed neutral carbonates, and
likewise that all carbonic acid determinations hitherto
attempted with the object of . measuring the carbonic acicl
present in sea-water were faulty. As regards the
carbonic acid determinations performed previous to the
publication of Dr. Jacobsens Memoir on the presence of air
in sea-water, such must as a matter of course be wholly
worthless, the method of distillation to dryness having in
no case been adopted, or that of concentrating the fluid
till further evaporation ceased to expel carbonic acid. The
<< prev. page << föreg. sida << >> nästa sida >> next page >>
