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.
Kulsyrebestemmelser pleiede han derfor altid for
Operationens Begyndelse at udfælde Svovlsyren med concentreret
Chlorhariumopløsning, forat Kulsyren lettere skulde
undvige, men anvendte forresten den af Dr. Jacobsen angivne
Methode, hvorved lian har bestemt Kulsyren i Søvandet i
de sydlige Have til i Middel 43.26 Mgr. per Litre1.
Da jeg Taaren 1877 opfordredes til at gaa ud som
Chemiker paa den norske Nordhavsexpeditions 2det Togt,
var der kun levnet mig nogle faa Dage til Forberedelser. .
og det følger derfor af sig selv, at jeg ikke paa nogen
Maade dengang kunde have befattet mig med vidtløftigere
Forundersøgelser, og jeg maatte saaledes uden selv at
kunne prøve optage de tidligere Methoder uforandrede.
Paa Togtet i 1877 anvendtes •derfor den af Dr. Jacobsen
angivne Methode, og bestemtes efter denne gjennem en
Række omhyggelig udførte Observationer Kulsyregehalten
i det da undersøgte Hav til omkring 100- Mgr. per Litre.
Der viste sig imidlertid ved Gjentagelse af samme
Observation bestandig Uoverensstemmelser, som ofte vare ikke
ubetydelige og engang endog løb op til hele 12 Mgr. per Litre.
Dels herved dels ved andre Omstændigheder vaktes
min Mistanke om Tilforladeligheden af den af Dr.
Jacobsen i Forslag bragte Methode.
Det syntes mig paa Forhaand overmaade urimeligt,
at der hos Søvandet skulde tindes en-saadan mærkelig Evne
til rent mekanisk at tilbageholde den ene Gasart, medens
den ingensomhelst Virkning skulde udøve paa de Andre.
Heller ikke var der nogensinde gjort noget Forsøg paa at
sætte dette Phænomen i Forbindelse’ med bekjendte
chemiske Egenskaber hos nogen af de i Søvandet indeholdte Stoffe.
Ved et Tilfælde kom jeg en Dag til at forsøge
Søvandets Reaktion paa Lakmus og Rosolsyre og fandt til
min store Forundring,. at det reagerede bestemt og
tydeligt alkalisk, hvad jeg siden har bragt i Erfaring, at
allerede v. Bibra2 og senere E. Guignet og A. Telles3 har
observeret.
Efter mine Forsøg viser to ligestore Prøver af en
efter Gottliebs4 Fremgangmaade frisk tilberedt
Lakmus-opløSning, hvoraf den Ene tilsættes en tilstrækkelig Mængde
Søvand og den Anden et ligestort Volum rent destilleret
.Vand, ikke ubetydelige Farvedifferentser. Ligeledes
antager en med meget fortyndet Oxalsyre svagt udsyret
passende Portion rent Vand. hvori paa Forhaand er opløst
en Draabe Rosolsyre. ved Tilsætning af Søvand strax d’en
bekjendte rødlig-violette Farve.
Paa denne Maade undersøgtes paa Expeditionens sidste
Togt, hvor der var fuld Anledning til at erholde
Vandprøverne ganske friske, et meget stort Antal af disse og
uden Undtagelse med det samme ovenbeskrevne Resultat.
acid, before - commencing the operation, by adding to the
water a saturated solution of chloride of barium, in order
to facilitate the liberation of the carbonic acid, but, with
this exception, adopted the method devised by Dr. Jacobsen,
and determined the mean amount of carbonic acid present
in the water of the Southern Seas to be 43.26mar per
litre.1
When invited, in the spring of 1877, to go out as
chemist to the Norwegian North-Atlantic Expedition, on the
second cruise. I had but a few days’ in which to make the
necessary preparations, and consequently no time being left
me for preliminary experiments. I was compelled to adopt
unchanged the earlier methods, without testing the accuracy
of their results. On the cruise in 1877, I therefore
applied Dr. Jacobsen s method, and determined by a series of
careful observations the amount of carbonic acid present
in the water of the tract then investigated to be about
100"’fr per litre. But, on repeating the operation with the
same sample of water, the results were always found to
vary, and frequently indeed considerably; nay, on one
occasion the difference amounted to as much as 12m♂r per litre.
Partly for this reason, and partly from other
circumstances. I was led to question the trustworthiness of
Jacobsen’s method.
• Now it struck me at once as highly improbable that
sea-water should possess so remarkable a power of
retaining mechanically one gas, and yet,, in this respect, exert no
influence whatever on others. Nor had any attempt been
made to connect this phenomenon with known chemical
properties distinguishing the substances contained in
sea-water.
Quite accidentally, I was one day led to investigate
the effect of sea-water as a reagent on litmus and rosolic
acid, and found its reaction, to my great surprise,
distinctly alkaline, which, indeed, as I subsequently learnt,
had been already observed, first by von Bibra2 and later
by E. Guignet and A. Telles.3
According to my experiments, two equal measures of
a solution of litmus, freshly prepared by Gottlieb’s method.4
one of which has added to it a sufficient quantity of
sea-water and the other an equal volume of pure distilled
water, exhibit considerable difference in colour. Moreover,
a proportionate mixture of highly dilute oxalic acid and
pure water, -the latter having been previously treated with
a drop of rosolic acid, will, on the addition of sea-water,
immediately assume the well known reddish-violet hue.
In this manner were examined on the last cruise of
the Expedition, which afforded excellent opportunities of
obtaining the water quite fresh, a very large number of
samples, and invariably with the results described above.
1 Ber. Berl. chem. Ges. 11 — 410.
2 Ann Chem. Pharm. 77 — 90.
3 Compt. rend. 83 — 919.
4 Journ. fur pract. Chem. 107 — 488.
1 Ber. Berl. chem. Ges. 11, p. 410.
2 Arfn. Chem. Pharm. 77, p. 90.
3 Compt. rend. 83, p. -919.
4 Journ. fiir pract, Chem. 107, p. 488.
<< prev. page << föreg. sida << >> nästa sida >> next page >>
