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31
Naar Søvandet i dette Apparat kogtes med fortyndet
Svovlsyre i en kulsyrefri Luftstrøm, undveg Kulsyren’ meget
hurtigt, idet 15 Minutters .Kogning fuldstændig strak til
for at bringe al Kulsyre over i Forlaget. Søvandets
Sulfater viste altsaa i alle Fald ikke ved Tilstedeværelsen af
fri Syre de af J. Y. Buchanan observerede Egenskaber.
Naar den paa denne Maade uddrevne Kulsyremængde
opsamledes og bestemtes, viste den sig altid at stemme
nogenlunde med, hvad man efter den af Dr. Jacobsen- aiivendte
Methode kunde erholde uddrevet, idet de optrædende
Afvigelser snart vare positive snart negative men i Regelen
ikke større, end at de for- den største Del maatte kunne
tilskrives Observationsfeil. ATed den af Buchanan i
Forslag bragte Udfældning af Svovlsyren erholdt jeg derimod
bestandig betydelig for låve Resultater, hvorom senere.
For samtidig i en og sam^e Portion at kunne
bestemme baade den neutralbundne og den samlede Mængde
Kulsyre, anvendte jeg følgende Fremgangsmaade.
Efterat Apparatet fuldstændig var befriet for
kulsyreholdig Luft, anbragtes i Forlaget paa den før beskrevne
Maade 25 CC. Barytvand, hvoraf hver CC. svarede til
4.129 Mgr. Kulsyre, hvorefter der i Kolben C heldtes
367.7 CC. af det til Undersøgelse bestemte Søvand
tilligemed 10 CC. af en Svovlsyre, hvoraf hver CC. svarede -til
4.099 Mgr. Kulsyre. Indholdet i Kolben ophededes nu
under Gjennemleduing af en meget langsom Luftstrøm til
Koghede og holdtes i Kog i nogen Tid. Efter Forløb af
henimod 15 Minutter fjernedes atter Varmekilden og
Vædsken afkjølecles, idet Luftstrømmen lidt efter- lidt gaves en
noget større Hastighed, hvorved den endnu ikke absorberede
Kulsyre meget hurtigt bragtes over i Forlaget.
Efter endt Operation bragtes de i F værende
Glaskugler tilligemed det ved Rørets Vægge heftende
Barytvand ned i Forlaget E, hvorpaa det Hele retitreredes med
en Oxalsyre, hvoraf hver CC. svarede til 3.976 Mgr.
Kulsyre, idet alkoholisk Curcuma tjente som Index. Ligeledes
skylledes den vecl de indre Vægge af Kjoleren heftende
Vædske ved lidt kulsyrefrit destilleret Vand ned i Kolben,
hvori den overskydende Syre neutraliseredes med en
Natronlud, hvoraf hver CC. svarede til 2.928 Mgr. 00,. idet •
Rosolsyre tjente som Index.
•
Som Resultat af clisse Titreringer erholdtes den
samlede Kulsyremængde bestemt til omkring 97 Mgr. og den
neutralbundne til gjennemsnitlig henimod 53 Mgr. pr. Litre.
De 44 Mgr. Kulsyre, som udgjør Differentsen mellem den
samlede Kulsyremængde og den neutralbundne, kan
aabenbart ikke forekomme i Søvandet som fri Gasart, men maa
forene sig med de allerede færdigdannede Carbonater under
Dannelsen af Bicarbonater, og det viser sig altsaa, at de
af Dr. Jacobsen gjorte Observationer meget naturligt lade
sig forklare derved, at Søvandet ikke indeholder det
mindste Spor af fri Kulsyre men hele 53 Mgr. neutralbunden
og kun omkring 44 Mgr. surtbunden Kulsyre pr. Litre.
On boiling sea-water along with diluted sulphuric
acid, exposed to a current of air free from carbonic acid,
in this apparatus, carbonic acid escaped very rapidly, the
space of 15 minutes sufficing to collect the whole of it in
the receiver. The sulphates in sea-water — at least when
free acids were present — did not, accordingly, exhibit the
properties ascribed to them by J. Y. Buchanan. On
collecting and determining the carbonic acid driven off by this
process, the amount was • invariably ’ found to agree with
that which could be liberated by Dr. Jacobsen’s method,
the differences observed having been sometimes positive and
sometimes negative, but as a ride not greater than would
admit of imputing them cliiefly to errors of observation. On
precipitating the sulphuric acid as suggested by Buchanan,
the results obtained were invariably too low; but to this
subject I åh all afterwards* return.
In order to determine both the proportion of carbonic
acid forming the neutral carbonates and the whole amount
of carbonic acid contained in one and the same sample of
sea-water. I adopted the following mode of procedure.
After expelling from the apparatus all air in which
carbonic acid was present, 25 M of baryta water were
introduced, as previously described, into the receiver, each
c.centim. representing 4.129m"r carbonic acid ; 367.7cc of the
sea-water to be examined were then poured into the
matrass (C), along with 10cc of sulphuric acid, each c.centim. of
which represented 4.099 "’fr carbonic acid. The contents
of the matrass were now heated, during exposure to a very
slow current of air, up to the boiling-point, and kept for
some time at that temperature. After the lapse of about
15 minutes, the source of heat was removed and the fluid
cooled, the rapidity of the current of air being slightly
increased, causing the carbonic acid not yet absorbed to
pass off quickly into the receiver.
The operation being terminated, the glass balls in
the tube F. along with the baryta water adhering to the
walls of the tube, were introduced into the receiver E. and
the whole of its contents retitrated with oxalic acid, each
•c.centim. of which represented 3.976mgr carbonic acid, a
solution of alcoholic curcuma serving as the index. The fluid
adhering to the walls of the cooler was likewise washed
down into the matrass with a little distilled water free from
carbonic acid, and the surplus acid neutralised by the
addition of soda-lye, each c.centim. of which represented 2.9.28"’-’"’
CO2, rosolic acid serving as the index.
As the result of this titration, the total amount of
carbonic acid was found to be about 97m♂r and the
proportion forming neutral carbonates to average about b’d""jr
per litre. Now, the difference, 44mgr, cannot occur free
as gas. but will unite with the carbonates to form
bicar-bonates; and hence Dr. Jacobsen’s observations could be
readily explained on the assumption that sea-water contains
no trace even of free carbonic acid, but as much as 53m,/r
per litre of carbonic acid forming carbonates and only
about 44m♂r per litre of carbonic acid forming
bicar-bonates.
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