27 



Kulsyrebestemmelser pleiede bau derfor altid før Operar 



tii mens Begyndelse at udfælde Svovlsyren med concentreret 

 CMorhaxiumppløsning, foråt Kulsyr&n lettere skulde und- 

 vige, men anvendte forresten den ai' Dr. Jacobsen angivne 

 Methode, hvorved han har bestemt Kulsyren i So våndet i 

 de sydlige Have til i Middel 43.26 Mgr. per Litre 1 . 



Da jeg Vaaren 1877 opfordredes til at gaa ud som 

 Ohemiker paa den norske Nordhavsexpeditions 2det Togt. 

 var der kun levnet mig nogle faa Dage til Forberedelser, 

 og det følger derfor af sig selv, at jeg ikke paa nogen 

 Maade dengang kunde have befattet mig med vidtloftigere 

 Forundersøgelser, og jeg maatte saaledes uden selv at 

 kunne prøve optage de tidligere Metlioder uforandrede. 

 Paa Togtet i 1877 anvendtes •derfor den af Dr. Jacobsen 

 angivne Methode, og bestemtes efter denne gjennem en 

 Række omhyggelig udforte Observationer Kulsyregehalten 

 i det da undersøgte Hav til omkring 100- Mgr. per Litre. 

 Der viste sig imidlertid ved Gjentagelse af samme Observa- 

 tion bestandig Uoverensstemmelser, som ofte vare ikke ube- 

 tydelige og engang endog lob op til hele 12 Mgr. per Litre. 



Dels herved dels ved andre Omstændigheder vaktes 

 min Mistanke om Tilforladeligheden af den af Dr. Jacob- 

 sen i Forslag bragte Methode. 



Det syntes mig paa Forhaand overmaade urimeligt, 

 at der hos Søvandet skulde tindes en.saadan mærkelig Evne 

 til rent mekanisk at tilbageholde den ene Gasart. medens 

 den ingensomhelst Virkning skulde udove paa de. Andre. 

 Heller ikke var der nogensinde gjort noget Forsog paa at 

 sætte dette Phænomen i Forbindelse' med bekjendte chemi- 

 ske Egenskaber hos nogen af de i Søvandet indeholdte Stoffe. 



Ved et Tilfælde kom jeg en Dag til at forsøge Sø- 

 vandets Reaktion paa Lakmus og Rosolsyre og fandt til 

 min store Forundring,, at det reagerede bestemt og tyde- 

 lig! alkalisk, hvad jeg siden har bra gt i Erfaring, at alle- 

 rede v. Bibra- og senere E. Guignet og A. Telles 3 har 

 observeret. 



Efter mine Forsog viser to ligestore Prover af en 

 efter Gottliebs 4 Fremgangmaade frisk tilberedt Lakmus- 

 opløsning, hvoraf den Ene tilsættes en tilstrækkelig Mængde 

 Sovand og den Anden et ligestort Volum rent destilleret 

 .Vand. ikke ubetydelige Farvedifferentser. Ligeledes au- 

 tager en med meget fortyndet Oxalsyre svagt udsyret pas- 

 sende Portion rent Vand. hvori paa Forhaand er oplost 

 en Draabe Rosolsyre. ved Tilsætning af Sovand strax den 

 bekjendte rødlig-violette Farve. 



Paa denne Maade undersøgtes paa Expeditionens sidste 

 Togt. hvor der var fuld Anledning til at erholde Vand- 

 prøverne ganske friske, et meget stort Antal af disse og 

 uden Undtågelse med det samme ovenbeskrevne Resultat. 



4io. 



90. 



1 Ber. Berl. cliem. Ges. 11 



2 Ann Chem. Pharm. 77 — 



3 Compt. rend. 83 — 919. 



4 Journ. fiir pract. Chem. 107 — 488. 



acid. before- commencing the operation, by adding to the 

 water a saturated solution of chloride of barium, in order 

 to facilitate the liberation of the carbonic acid. hut. with 

 this exception. adopted the method devised by Dr. Jacobsen, 

 and determined the mean amount of carbonic acid present 

 in the water of the Southern Seas to be 43.26'"»'' per 

 litre. ' 



When invited, in the spring of 1877. to go out as 

 chemist to the Norwegian North- Atlantic Expedition, on the 

 second cruise. I had hut a few days' in which to make the 

 necessary preparations, and consequently no time being left 

 me for preliminary experiments, I was compelled to adopt 

 unchanged the earlier methods. without testing the accuracy 

 of their results. On the cruise in 1877, I therefore ap- 

 plied Dr. Jacobsens method. and determined by a series of 

 careful observations the amount of carbonic acid present 

 in the water of the tract tben investigated to be about 

 10( i "'■•"• j»er litre. But. on repeating the operation with the 

 same sample of water, the results were always found to 

 va ry. and frequently indeed considerably ; nay, on one occa- 

 sion the differ.ence amounted to as much as 12 M » r per litre. 



Partly for this reason, and pavtly from other circum- 

 stances. I was led to question the trustworthiness of 

 Jacobsen's method. 



• Now it struck me at once as highly improbable that 

 sea-water should possess so remarkable a power of retain- 

 ing mechanically one gas, and yet,. in this respect. exert no 

 infhience whatever on others. Nor had any attempt been 

 made to connect this phenomenon with known chemical 

 properties distinguishing the substances contained in sea- 

 water. 



Quite accidentally, I was one day led to investigate 

 the effect of sea-water as a reagent on litmus and rosolic 

 acid. and found its reaction, to my great surprise, cbst- 

 inctly alkaline. which. indeed. as I subsequently learnt. 

 had been already observed. first by von Bibra- and later 

 by E. Guignet and A. Telles. 3 



According to my experiments. two equal measures of 

 a solution of litmus. freshly prepared by Gottliehs method. 4 

 one of which has added to it a sufficient quantity of sea- 

 water and the other an equal volume of pure distilled 

 water, exhibit considerable difference in colour. Moreover. 

 a proportionate mixture of highly dilute oxalic acid and 

 pure water, 'the latter kaving been previously treated with 

 a drop of rosolic acid. will. on the addition of sea-water. 

 immediately assuine the well known reddish-violet hue. 



In this manner were examined on the last cruise of 

 the Expedition. which afforded excellent opportunities of 

 obtaining the water quite fresh. a very large nuniber of 

 samples, and invariably with the results described above. 



1 Ber. Berl. chem. Ges. 11, p. 410. 

 - Anii. Chem. Pharm. 77, p. 90. 



3 Compt. rend. 83, p. S19. 



4 Journ. fiir pract. Chem. lo7. p. 488. 



4* 



