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43
velser Intet med Bestemtlied kan slutte 0111 Carbonaternes
Mængde i de store Verdenshave. Dét synes dog, som om
de af- Buchanan udførte Bestemmelser af Kulsyren i
Atlanterhavet, (hvorved han inddamper efter forudgaaende
Tilsætning af Chlorbarium og tilslut med stærk Saltsyre
forgjæves har bestræbt sig for at paavise Kulsyre i Residuet),
med Sikkerhed skulde fastsætte en øvre Grændse for den
tilstedeværende Carbonatmængde, men dette er i
Virkeligheden ikke Tilfælde.
Som bekjendt beskytter uopløselige Sulfater
Carbona-ter mod Decomposition endog, naar til Uddrivelse af
Kulsyren anvendes saa radicale Midler som concentreret
Svovlsyre. saaledes at man endog af den Grund har fundet det
fornødent at modificere den af Fresenius og Will angivne
Methode til Bestemmelse af Kulsyren i neutrale Carbonater.1
De af Buchanan foretagne Undersøgelser efter Kulsyre i
Residuet kan derfor ikke betragtes som Bevis for. at den
ikke skulde have været tilstede, og det fremgaar ogsaa
tydeligt af hans egne Udtalelser, at han selv .har været af
samme Mening.
Forat faa Rede paa, hvorvidt en ved Kogning
bevirket Decomposition af de i Søvandet indeholdte neutrale
Carbonater foregaar i større Udstrækning ogsaa, naar der
i Vædsken findes uopløselige Sulfater, har jeg udført nogle
Forsøg efter den af Buchanan foreslaaede Fremgangsmaade.
Af nogle Vandprøver, som. udersøgte efter den af mig
benyttede Methode, viste sig at indeholde en Sum af
surtog neutralbunden Kulsyre af 90 Mgr. pr. Litre og
derover, erholdtes ved Inddampning til Tørhed efter
Tilsætning af Chlorbarium uddrevet kun henimod 50 Mgr.,
ved en enkelt Undtagelse erholdtes engang over 50 Mgr.
pr. Litre. Det vil sige, den uddrevne Kulsyremængde var
ikke synderlig høiere end den af Buchanan for Vandet i
Æqtatoregnene angivne og beløb sig til kun faa Mgr. over.
hvad den surtbundne Kulsyre efter paalidelige
Observationer skulde beløbe sig til, de endnu i Residuet
tilbageværende Carbonater lykkedes det heller ikke mig at paavise.
Spørgsmaalet oiu Carbonaternes Mængde i de sydlige
Have maa derfor endnu betragtes som aabent.
Forhaabentlig resterer endnu en Del af de fra
Chal-lengerexpeditionens Togter hjembragte Vandprøver, og man
vil i saa Fald ved Undersøgelse af disse kunne give
Bidrag til Besvarelsen af disse Spørgsmaal.
Efterat Ovenstaaende var nedskrevet paa Norsk, men
førend det endnu var oversat paa Tysk, ankom hertil 2det
og 3die Hefte for 1879 af Fresenius’ Zeitschrift fiir anal.
Chem., hvori E. Bohlig offentliggjør en Afhandling,2 hvoraf
det sees, at han ved Arbeide med naturlige Mineralvande
har observeret Omsætninger mellem kulsur Kalk og svovl-
of lime. From what has been-already explained, it is
obvious that nothing definite can be inferred from earlier
statements respecting the proportion of carbonates in the
water of the great oceans. The carbonic acid
determinations performed by Buchanan with water from the Atlantic
Ocean (lie had recourse to evaporation, adding first chloride
of barium, and then attempting, unsuccessfully, to detect
carbonic acid in the residue by means of strong
hydrochloric acid) would appear to fix a limit for the maximum
amount of carbonates contained in sea-water; but such is
not really the case.
The presence of insoluble sulphates serving, as is
known, to protect carbonates against decomposition, even
when concentrated sulphuric acid is made use of to expel
the carbonic acid, it was necessary for this reason alone
to modify the process devised by Fresenius and AVill for
determining carbonic acid in neutral carbonates.1 Hence,
the experiments performed by Buchanan with a view to
detect carbonic acid in the residue, cannot be regarded as
affording conclusive proof of its absence; indeed, he himself,
as appears from his statements, is clearly of the same opinion.
In order to ascertain whether the decomposition by
boiling of the neutral carbonates in sea-water also took
place to a considerable extent when insoluble sulphates
were present in that fluid, I made a few experiments by
Buchanan’s process. From several samples of sea-water
which,- examined by the. method 1 adopted, were found to
contain 96""’’ of carbonic acid per litre. I succeeded, by
evaporation to dryness, after adding a solution of chloride
of barium, in liberating about 50 m,Jr only, with a solitary
exception, when the amount exceeded 50 m♂r per litre. The
proportion of carbonic acid expelled was accordingly not
much greater than that determined by Buchanan in water
from the Equatorial Seas, and but a few millegrammes in
excess of what the carbonic acid forming bicarbonates,
according to trustworthy observations, should have been; of
the carbonates said to be still present in the residue, I
failed to detect any trace.
The amount of the carbonates contained in the water
of the Southern Seas must, therefore, be still regarded as
an open question.
It is to be hoped, that some of the samples of water
collected on the ’Challenger Expedition still remain, in
which case their examination will serve to throw further
light on the subject.
After this Memoir had been written in Norwegian,
but previous to its translation into German, the 2nd and
3rd Parts of Fresenius’ Zeitschrift fiir anal. Chemie for
1879 came to hand, in which ’E. Bohlig has published a
paper2 on transformations, observed by him in mineral
waters, resulting from the reciprocal action of carbonate of
1 Fresenius, Qvant. Analyse, nte Aufl. 364 bb.
2 Fresenius’ Zeitschrift, 18 — 195.
1 Fresenius, Qvant. Analyse, .">te Aufl. 304. bb.
2 Fresenius’ Zeitschrift, is, p. 19.’».
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