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4
0 4- N pr. Litre 16.0 ’ 16.2
0 + N= 100 0 °/o 3>-4 33-2
iV°/o 8 68.5 . 66.8
I Aaret 1869 udgik fra Englaud
Porcupiueexpeditio-nen. hvor der for første Gang forudeu de øvrige
videnskabelige Arbeider ogsaa foresloges udført mere omfattende
chemiske Undersøgelser. Man besluttede her at benytte
den udmærkede Anledning til ved talrige Forsøg saavel
med Overfladevand som Vand fra større Dyb at skaffe sig
Oplysning om de Fluctuationer, soin optræde saavel i de
absolute som relative Mængder af ele i Søvandet opløste’
Gasarter. . Forat undgaa de Feil. som nødvendigvis maatte
indsnige sig, naar de til Gasanalyser bestemte Vandprøver
opbevaredes i længere Tid før Undersøgelsen, bestemte man
sig her for den Uclvei at foretage Gasanalyserne ombord.
Til Optagelse af de fra større Dyb stammende Vandprøver
benyttedes en meget simpel Vandhenter bestaaende af en
hul Metalcylinder med letbevægelige opadslaaende
Kegle-ventiler, et Apparat, hvis paalidelighed senere Undersøgelser
giver Anledning til at betvivle. Udkogningen og
Opsamlingen af Gasarterne foretoges i alt Væsentligt som véd de
tidligere beskrevne Forsøg, og anvendtes uncler Analysen til
Absorbtion af Kulsyre og Surstof Kalihydrat og
pyrogal-lussur Kali. Det siger sig selv. at de paa denne Maade
erholdte Resultater maatte være beheftede med meget
betydelige Observationsfeil, hvad der ogsaa tydeligst vises af
de store Afvigelser mellem de af forskjellige Observatorer
efter denne Fremgangsmaade udførte Bestemmelser. Som
Udtryk for Sammensætningen af den af Overfladevandet
udkogte Luft fandt nemlig de tre Chemikere. soin paa de
tre Togter, hvori denne Expedition deltes, efter hinanden
udførte de chemiske Arbeider, følgende Tal:1
O -f- N pr. Litre i6.o 16.2
O p.ct. 31.4 33.2
iVp.ct. 68.5 66.8.
In the year 1869, the ’Porcupine’ Expedition was
dispatched by the British Government, and it was now
proposed, for the first time, to institute a series of chemical
experiments on a more comprehensive scale than any hitherto
performed. By taking advantage of this excellent
Opportunity to examine numerous samples of sea-water, both
from the surface and from great depths, the fluctuations
that occur alike in the absolute and the relative amounts
of gaseous bodies in ocean-water might be effectively
investigated, In order to guard against the error that
must necessarily arise when the samples of water are
preserved’ for any length of time previous to examination, it
was resolved to undertake all analyses of gas on board.
For obtaining samples of water from great depths, a very
simple instrument was used, consisting of a hollow metal
cylinder, furnished with conical-shaped valves, opening above,
an apparatus the trustworthiness of which subsequent
experiments have shown reason to doubt. The gas was boiled
out and collected. by a process essentially similar to that
adopted for the experiments previously described, the
carbonic acid and the oxygen having been absorbed by
hydrate of’ potash and pyrogallic acid. . As a matter of course,
very considerable .errors of observation would attach to
results obtained by this method, the best proof of which
lies in the extent to which the ’determinations of different
observers performed by this mode of operation are found
to vary. For instance, the three chemists who successively
accompanied the Expedition on the three voyages into which
it was divided, express the composition of the air boiled
out of surface-water by the following figures:1 —
W. L. Carpenter . . . . 31.6 °/0 O mod 68.4 ®/„ N.
Hunter.........36.4 - O - 63.6 - N.
P. Herbert Carpenter . . . 30.5 - O - 69.5 - N.
Dette er kun de af de enkelte Observationer
udledede Middelværdier, men, som man ser, er allerede
Afvigelserne mellem disse overmaade store, medens de enkelte
Bestemmelser, som ikke findes opførte, varierer mellem
langt videre Grændser. Saaledes opføres som
Ydergrænd-ser for Variationerne af Surstofmængden i Overfladevandet
Maximum 45.3 og Minimuhl 14.0 °/0 af den samlede
Gas-mængde, Kulsyren iberegnet.
Porcupineexpeditionens Chemikere ansaa selv sine Re- ’
sultater upaalidelige, dog mindre paa Grund af Mangler
ved Arbeidsmethoderne, end fordi den af dem benyttede
Vandhenter tillod Undvigelsen af den Luft, som de mente
kunde udvikle sig, naar Vandet fra de større Dyb naaede
op til det ved Overfladen herskende mindre Tryk. 1 )e tog
forresten sin Tilflugt ogsaa til andre Midler for at forklare
AV. L. Carpenter. . . 31.6 p.ct. O and 68.4 p.ct. N.
Hunter......36.4 - O - 63.6 - N.
P. Herbert Carpenter . 30.5 -’O - 69.5 - N.
These amounts, however, are the mean values deduced
from the several observations, and yet they vary
exceedingly; the individual determinations, which are not given,
must obviously have ranged between far wider limits. Thus,
the extreme limits between which the amount of oxygen
was found to vary in surface-water, is stated to have been
45.3 (maximum) and 14.0 (minimum) per cent of the total,
amount of gas, including the carbonic acid.
• The chemists- who accompained the ’Porcupine’
Expedition did not even themselves regard the results obtained
as trustworthy, less however 011 the ground of possible
defects in the modes of operation, than because the the
apparatus used for collecting the water admits of the escape
of air which, in their opinion, may be liberated on water
drawn from great depths reaching the surface, where the atmos-
1 Proc. Roy. Soc. 18 — 397.
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