Som man ser. ev den lier til Bestemmelse nt den 
neutralbundne Kulsyre anvendte Methode i alt væsentligt 
den samme, som allerede for flere A ar tilbage er beskre- 
ven af Dr. Mohr. 1 Forskjellen stikker kun deri. at jeg 
har anvendt Classfens Kjøler og desuden ombyttet Salpeter- 
syren med Svovlsyre. I)et syntes mig nemlig ikke tilraa- 
deligt at anvende Salpetersyre ligeoverfor et saa stærkt 
cblorboldigt Mineralvand som Søvand, hvori der desuden 
fandtes en vel mærkbar om end temmelig liden Qvantitet 
oxyderbare Stoffe. 
Elter denne Fremgangsmaade har jeg senere ved 78 
Observntioner bestemt Kulsyren i 64 forskjellige Vandprø- 
ver temmelig jevnt fordelte over det af den norske Nord- 
havexpedition undersøgte Felt. Resultaterne Andes sam- 
menstillede i Tabel 11. . • 
Først skal i Korthed berøres de Feil. hvormed de i 
Tabellen opførte Tal kan tænkes beheftede. 
Om man vikle antage. at den i Søvandet indeholdte 
Kiselsyre ikke forekom opløst som fri Syre, men forefandtes 
bundet til Baser i Form af Silicater. en Antagelse af me- 
get tvivlsom Berettigelse, vilde man aabenbart efter den 
ovenfor beskrevne Methode fan noget feilagtige Resultater, 
idet den til Kiselsyre bundne Mængde Baser vilde Andes 
som hunden til Kulsyren. Fornt kunne danne mig en 
Forestilling om, hvorvidt den Feil. som man under denne 
Forudsætning skulde kunne begaa, nogensinde vil kunne 
tænkes at faa særlig Betydning, har jeg bestemt Kiselsyre- 
mængden i forskjellige af de hjembragte Vandprøver, idet 
følgende .Fremgangsmaade er kømmen til Anvendelse. 0.5 
Litre Søvand inddampedes med lidt Saltsyre i en Platina- 
skaal først over fri Ild senere paa Yandbad til Tørhed 
og tørredes ved 110° — 120° C. Saltene udtoges derpaa 
og pulveriseredes bedst muligt i en vel poleret Agatrive- 
skaal. hvorpaa de atter tørredes ved samme Temperatur, 
og sluttelig bragtes over i et passende Kar og tilsattes 
ca. 200 CO. saltsyreholdigt Vand, hvorved al Gips fuld- 
stamdigt opløstes. De paa denne Maade udskilte Kisel- 
Syremængder vare altid meget smaa og maatte nærmést 
blive at betegne som Spor. idet de. hvor jeg forsøgte at 
veie dem. kun beløb sig til Brøkdele af Mgr. i den an- 
vendte Portion Vand. Dette stemmer paa det Nøieste 
med. hvad Thorpe og Morton nylig har fundet i det irske 
Hav, 2 hvorimod de ældre Opgaver giver noget større Tal. 
Og man vil saaledes se, at der ingensomhelst Rimelighed 
er for. at den i Søvandet indeholdte Kiselsyremængde skulde 
bidrage til i mærkelig Grad at gjøre de fundne Resultater 
upaalidelige. 
Naar man skal danne sig en Mening om Nøiagtighe- 
den af disse Observationer. er det imidlertid nødvendigt 
at tage Hensyn til en anden Omstændighed, som kunde 
tænkes at have liavt sin Indflydelse paa Resultaterne. 
As will be seen, the method adopted lor the determ- 
ination of the carbonic acid forming carbonates, was es- 
sentially the same as that described by Dr. Mohr 1 several 
years previously. The only difference lay in my having 
employed Classen’s cooler and made choice of sulphuric 
acid in preference to nitric. It did not seem advisable to 
use nitric acid when examining a mineral water so rich 
in chlorine as is sea-water, and which besides contains a 
quantity, small indeed but appreciable, of organic matter. 
By this process I subsequently determined the car- 
bonic acid in 64 different samples of sea-water, drawn at 
comparatively regular intervals from the tract of ocean in- 
vestigated on the Norwegian North- Atlantic Expedition; 
the number of observations amounted to 78. The results 
are given in Table II. 
I will flrst say a few words respecting the errors 
that may possibly affect the accuracy of the flgures set 
down in the Table. 
Assuming the silicic arid in sea-water not to occur 
as a free acid, but combined with bases in the form of 
silicates, an .hypothesis of very doubtful value, the results 
obtained by the method described above would be obviously 
to some extent inaccurate, inasmuch as the bases com- 
bined with silicic acid must in that case have behaved as if 
originally combined with carbonic acid. In order to ascertain 
what importance could possibly be attached to an error 
arising on such an assumption, I determined the amount of 
silicic acid in divert of the samples of sea-water brought 
home with me, adopting for that purpose the- following 
method. Five-tenths of a litre of sea-water mixed with a 
little hydrochloric acid were evaporated to dryness in a 
platinum dish, at Arst over a common Are and then in a 
water-bath, and dried at a temperature of 110° — 120“ C. 
The salts were then taken out and transferred to a well 
polished agate dish, in which they were Anely pulverised, 
and again dried at the same temperature ; Anally they were 
placed in a suitable vessel, and mixed with about 200 « 
of water containing hydrochloric acid, which thoroughly dis- 
solved all the gypsum. The amounts of silicic acid thus 
precipitated were invariably very small, indeed but little 
more than traces; for. on attempting to weigh them, they 
proved to be but fractions of a milligramme. This result 
agrees exactly with the observations of Thorpe and Morton 
on water from the Irish Sea, 2 whereas the flgures in ear- 
lier statements are somewhat higher. Ht*nce, there is no 
reason whatever to assume, that the silicic acid present in 
sea-water should to any considerable extent influence the 
results obtained. 
When judging of the accuracy of these observations, 
regard must, however, be bad to another circumstance that 
might possibly in some measure affect the results. The 
water examined did not consist of freshly drawn samples, 
1 Mohr Titrirmethode 3te AuH. — 524. 
4 Ann. Chem. Pharm. 158 — 122. 
1 Mohr’s Titrirmethoden 3te Aufl. p. 524. 
4 Ann. Chem. Pharm. 158, p. 122. 
