17 



til i Middel 34.96 og for det i 1878 undersøgte melleni 

 70de og 80de Breddegrad beliggende Strøg til 35.64 ",,,. 

 Fuldstændigt tilsvarende er det af Buchanan fundet al 

 være paa den sydlige Balvkugle, idet Surstofprocenten i 

 Overfladen der varierer fra omkring 33 i ZEqvåtoregnene 

 til ca. .'!•") omkrin;: den sydlige Polarcirkel. 



Dette lod med temmelig stor Bestemthed formode, 

 at de for destilleret Vand gjældende, af Bunsen opstillede, 

 Absorbtionscoefficienter ikke skulde være gyldige for Søvand, 

 idet det. uaar < >verfladevandsluftens Sammensætning fandtes 

 at variere med Bredden, maatte være det Naturligste at 

 skrive diss ( - Variationer paa Temperaturforandringerne. Det 

 vil imidlertid ikke fore til noget rimeligt Resultat, om man 

 vil betragte Temperaturen som den Variable og af de her 

 foreliggende Observationer forsøge at adlede en Lov for 

 Absorbtionscoefficienternes Variationer med Temperaturen. 

 Man vil da tinde, at de enkelte Observationer staa ikke 

 ubetydeligt i Strid med hinanden, idet der for Surstof- 

 mængdernes Vedkommende overalt optræder meget større 

 Afvigelser, end man kan antage begrundede i Observations- 

 feil. Det kuncle dog ikke savnes tilraadeligt at lade det 

 bero hermed og forsøge at discutere de foreliggende Ob- 

 servationer uden nøiere Kjendskab til Absorbtionscoeffici- 

 enternes Afhængighed af Temperaturen, og jeg besluttede 

 derfor at bestemme saavel Sammensætning som Mængde af 

 den i Søvandet ved forskjellige Temperaturer opløste Luft. 



Først gjordes en Del Forsøg. hvorved Søvandet i et 

 Bad af constant Temperatur søgtes mættet ved flere Timers 

 Gjennemledning af Luft. (saaledes som Bunsen har gaaet 

 frem ved sine Bestemmelser 1 ), hvoretter den opløste Luft 

 uddreves og analyseredes paa den for beskrevne Maade. 

 De paa denne Maade mættede Vandprover afgave bestan- 

 dig Luftmængder, som uden Hensyn til den Temperatur, 

 hvorved Våndet var mættet, viste nogenlunde nær den 

 samme Sammensætning (med 34.9 ",,, Surstof mod 65.1 ",, 

 Kvælstof), medens de ofte temmehg stærkt afvigende Tal. 

 som udtrykte de absolute Mængder af opløste (Jaser, tyde- 

 ligt. viste, , at der paa denne Maade ikke var opnaaet fuld- 

 stændig Mætning. 



Professor Waage foreslog mig derfor at gjentage disse 

 Forsøg med nogen Variation i den Maade. hvorpaa Mæt- 

 ningen iværksattes, og har jeg som Folge deraf ved de 

 senere Forsøg benyttet følgende Fremgangsmaade. En pas- 

 sende Portion Søvand af nogenlunde høi Bgenvægt rystedes 

 med Luft i en rummelig Kolbe i et Tidsrum fra 1 til 2 

 Timer under stadig Yexlen af den i Kolben værende Luft 

 og hensattes derpaa i nogle Timer ganske rolig, idet Tem- 

 peraturen saavel under Rystningen som senere holdtes fuld- 

 stændig constant. Foråt overbevise mig om, at jeg har 

 opnaaet fuldstændig Mætning, har jeg nærmet mig Mæt- 



Norwegian Expedition in 1876 and 1877, amounts to 34.96. 

 and for that Iving between the 70th and 80th parallels of 

 latitude, to 35.64 per cent. Buchanan observed precisely 

 the same phenomenon in the southem bemisphere, the 

 proportion of oxygen varying from about 33 per cent in 

 the Equatorial Seas to about 35 per cent in the vicinitv oi 

 the Ahtarctic ' lircle. 



Eleasoning on these data. there «ere strong grounds 

 to assume, that the coefficients of absorption given by 

 Bunsen for distilled water could not apply to sea-water; 

 for, the composition of the air in surface-water having been 

 found to vary with the latitude, the most probable cause 

 of this phenomenon would seem to be temperature. Mean- 

 while, we shall not arrive at a satisfactory result by regard- 

 ing temperature as the variable factor, and by seek- 

 ing from the observations here set forth to discover a 

 law according to which the coefficients of absorption 

 vary with the temperature. The individual observations 

 would in that case he found to clash. inasmuch as the 

 variation with regard to oxygen is invariably greater 

 than can be assumed to arise from errors of observation. 

 However. it did not seem advisable to leave the. question 

 as it stood, and proceed to the discussion of the results 

 without having further investigated the relation of the co fti- 

 cients of absorption to the temperature: and I resolved, there- 

 fore. on determining alike the composition and the amount 

 of the air absorbed by sea-water at different temperatures. 



A series of experiments were first instituted with 

 a view to saturate sea-water with air. viz. by placing 

 it in a bath of constant temperature. and for the space 

 of several honrs uninterruptedly conducting through it a 

 current of air. — the mode of operation adopted by 

 Bunsen for his deterrainations. 1 — after which the air ab- 

 sorbed in the water was driven off. and analysed by the 

 process previously described. The samples of water satu- 

 rated in this manner invariably yielded quantities of air 

 which. irrespective of the temperature at which the water 

 bad been saturated. were found to be very nearly uni- 

 form in composition. viz. 34.9 per cent oxygen and G5.1 per 

 cent nitrogen, whereas the figures, otten widely div.ergent, 

 expressing the absolute quantities of the gaseous bodies 

 absorbed. gave sufticient proof that by this method complete 

 saturation bad not been attained. 



At Professor Waage's suggestion. I rejæated these 

 experiments. varying slightly the means by wbich satura- , 

 tion was sought to be effected, and have since .adopted the 

 following mode of operation. A quantity of sea-water. of 

 considerable specific gravity. is shaken, along with air. in 

 a roomy matrass for one or two hours. the air in the 

 matrass being frequently renewed. and flien lett perfectly 

 still for a few hours. at the precise temperature preserved 

 during its continual agitation. To be quitesure tbat I have 

 really succeeded in saturating the water. I approach the 

 point of saturation as it were from opposite directious: 



Bunsen. Gasom. Jlethoden — lii.">. 



Den norske Nordhavsexpedition. Tornne: Chemi. 



1 Bunsen, lia^ini. Methoden, p. 105. 



