35 
udtort en Ra*kke Forsøg til Bestemmelse af de organiske 
Stoffes Mængde, om at meddele mig de foraødtfe Data. 
Ifølge ham ere de organiske Stoffes Mængde kun under- 
kastet meget srnaa Variationer, og affarver 1 Litre So- 
vand gjennemsnitlig 3 Mgr. Kamæleon, som under Forud- 
sætning af Reduction til Oxydulsalt kun kan afgive hen- 
imod 0.8 Mgr. Surstof, hvoraf det lettelig vil kunne indsees, 
at den dannede Mængde Kulsyre ikke kan være meget 
stor. naar Surstofforbruget selv ved en saa energisk Oxyda- 
tion som ved Anvendelse af Kamadeon er saa lidet. .Og 
hvad der især tyder paa. at den Oxydation. som kan 
foregaa ved jVandprøvens Henstand under ordinære For- 
holde, fuldstændig maa kunne negligeres, er den Om- 
stændighed, at Schmelck har fundet Søvandets Evne til 
at affarve Kamæleon ligestor. hvadenten Yandprøven under- 
søges' frisk eller først efter aarelang Henstand. 
At noget afKulsyren ved den lauge Henstand skulde 
være fordampet, er der heller ingen Rimelighed for. naar 
man erindrer, at Søvandet er en alkalisk Vædske, som 
ikke indeholder det mindste Spor af fri Kulsyre, og som 
med saadan Kraft holder paa sin surt bundne Kulsyre'. at 
den i timevis kan koges i det af Jacobsen angivne Luft- 
udkogningsapparat med det Resultat, at kun en meget 
liden Brøkdel uddrives. Der er aabenbart større Fare for 
det Modsatte. nemlig at der skulde kunne absorberes noget 
af Atmosphærens Kulsyre. men for Undgaaelseu af denne 
Feilkilde er der sørget ved omhyggelig Opbevaring paa 
velproppede Flasker. 
Resultaterne synes heller ikke at tyde paa. at Hen- 
standen skulde have været til Skade for VandprøverneS 
Brugbarked. idet de alle uden Hensyn til den meget for- 
skjellige Yarighed af det Tidsrum. hvori de have henstaaet, 
vise nogenlunde det samme Resultat, og jeg tror saaledes 
ikke at tage meget Feil. naar jeg anser de af mig udførte 
Observationer som. i alt Væsentligt ligesaa gode, som om 
de havdé været udførte ombord paa friskt optagne Yand- 
prøver. 
Hvad angaar de af selve Methoden og Experimenta- 
tionen flydende Observationsfeil, da vil de hyppigt udførte 
Controlhesteminelser kunne give de fornødne Bidrag til 
Bedømmelsen af deres Størrelse, saaledes tr ved 13 Con- 
trolbestemmelser for .den neutralt bundne Kulsyres Yed- 
kommende den gjennemsnitlige halve Differents mellem 2 
paa samme Yaudprøvc udførte Observationer bestemt til 
0.11 Mgr. per Litre (Maximum 0.6) og for den surt 
bundne Kulsyres Yedkommende til 0.59 Mgr. per Litre 
(Maximum 1.35). Foruden den variable Feil vil der imidlertid . 
i sidste Tilfælde ogsaa være en constant, idet det ikke 
lader sig undgaa. at man ved Arbeide i en kulsyreholdig 
Atmosphære vil erholde noget om end meget lidet for hoie 
Resultater. Naar Feilene ved Bestemmelsen af den surt 
bundne Kulsyre er lunden at være størst, da er G runden 
dertil for en stor Del at søge deri, at man ved Retitration 
med Natronlud. især naar Rosolsyre anvendes som Index, 
erholder en meget skarp Endereaction. raedens dette paa 
lang Yei ikke i samme Grad er Tilfælde. hvor Barvt re- 
ine with the necessary data. According to his ohserations. 
the amount of organic matter varies but very slightly. 
1 litre of sea-water discolouring on an average 3 m * p per- 
manganate ot potash: and this quantity, assuming extreme 
reduction, cannot give off more than about 0.8”'? r of oxygen. 
Hence it is obvious that the amount of carbonic acid can- 
not be very large, considering the limited consumption of 
; oxygen even with the use of permanganate of potash. But 
that the oxidation which can ordinarily result from allow- 
ing the water to stand over may be altogether ignored, 
is more particularly indicated by the fact of Schmelck hav- 
ing found the property in sea-water of discolouring perman- 
I gaijate ot potash to he invariably the same, whether the 
samples are freshly drawn or have been preserved for years 
together. 
Nor is there reason to assume, that any portion of 
the carbonic acid should have escaped by evaporation dur- 
ing the long interval, if we bear in mind that sea-water is 
an alkaline fluid, which does not contain the smallest trace 
of free carbonic acid, and which retains that present in 
bicarbonates with such vigour., that it may he boiled for 
hours together in the apparatus devised by Jacobsen for 
boiling out air and not part with more than a mere frac- 
tion. Nay, there is obviously danger of the reverse, viz. 
that some of the carbonic acid present in the atmosphere 
will be absorbed; but that source of error was effectually 
avoided by keeping the water iu bottles provided with 
tight-fltting glass stoppers. 
Judging, too. from the results, which were very nearly 
the samé for all the samples, irrespective of the difference 
in the length of the period during which they had been 
preserved, the interval that had elapsed previous to examin- 
ation did not appear to have had any injurious effect on 
the water for experimental purposes; and hence I feel 
tolerably convinced that my observations in all essential 
particulars are as reliable as if they had, been conducted 
| on board with freshly drawn water. 
With respect to the errors of observation involved in 
the method itself, numerous test-determinations will serve 
as an approximate standard by which to compute their 
magnitude; thus, for instance, half the difference between 
two observations with the same sample of water was found, 
for the carbonic acid forming carbonates, to be 0.1 1'"' 7 '' per 
litre (maximum 0.6). and for the carbonic acid forming bi- 
carbonates to be 0.59"^ r per litre (maximum 1.35). Exclusive 
of the variable error there will also, in the latter case, be 
a constant one, inasmuch as the results of experiments 
performed in an atmosphere containing carbonic acid must 
necessarily be somewhat, if hut a very little, too high. 
When the error in the determination of the carbonic acid 
forming bicarbonates is found to he greatest, the reason 
will be chiefly this, that retitration with soda-lye. more espe- 
cially if rosolic acid has been selected as the index, gives 
rise to a very decided -terminal reaction, which does not 
result on the baryta water being titrated with oxalic acid : the 
reaction is then muph less obvious. It must be likewise 
