III. Om Salthojdighedenaf Våndet 



i det norske Nordhav. 



Hvor det gjælder at tilveiebringe Oplysninger om Varia- 

 tiouerne af Saltmængderne i Havvandet. kan man til 

 sine Saltbestemmélser benytte flere forskjellige Methoder, 

 som liver især tidligere bar fundet udstrakt Anvendelse. 

 Den nærmest liggende at' disse bestaar i Våndets Afdamp- 

 ning og derpaa følgende Tørring og Verning af de som 

 Residuum tilbageblivende Salte, en Fremgangsniaade, som 

 rigtignok directe fører til Maalet, men som- til Grjengjæld 

 ogsaa fordrer temmelig meget Arbeide. Som mere indi- 

 recte men ogsaa ulige mindre besværlige Methoder kan 

 ogsaa anvendes Bestemmelse af Havvandets Cblormængde 1 

 eller Egenvægt, hvoraf man gjennem passende bestemte 

 Coefficienter .kan beregne den samlede Saltmængde. forud- 

 sat. at man kan antage et constant indbyrdes Forhold 

 mellem de i Sovandet fndeholdte faste Bestanddele. Den 

 første af disse Methoder medfører foruden Besværligheder 

 ved Udførelsen ogsaa den Ulempe, at den ikke lader sig 

 anvende ombord paa et Fartøi i aaben Sø. hvor Skibets 

 Bevægelser forbyder Brugen af Vægt. medens Egenvægts- 

 bestemmelser ved Hjælp af Aræometre og volumetriske Chlor- 

 bestemmelser meget letvindt og med temmelig stor Nøiag- 

 'tighed kan udfores ombord selv i temmelig nroligt Veif. 



Hvor man derfor ikke tror sig sikker paa at kunne 

 opbevare Vandprøverne i hengere Tidsrum uden derved at 

 risikere, at de undergaa Forandringer, som kunde ytre en 

 skadelig Indflydelse paa Resultatevne af de erholdte Salt- 

 bestemmélser og. hvor man som Folge deraf maa lægge 

 Hovedvægten paa en hurtig Undersøgelse af Vandprøverne 

 i frisk Tilstand, bliver man saaledes udelukkende henvist 

 til Brugen af Chlorbestemmelser eller Egenvægtsbestemmel- 

 ser som Maal for den samlede Saltgehalt, 



Paa det første af den norske Expeditions Togter blev 

 af Svendsen, hvem de chemiske Observationer dengang vare 



1 Saavel her som overalt senere forstaaes ved Chlormængde den 

 samlede Chlor- <>u BroiiinueiiLrde. 



III. (hi the Amoimt of Salt 

 in the Water of the Norwegian Sea. 



¥hen seeking to investigate the degree in which the 

 proportion of salt varies in sea-water. choice may be 

 made for performing the salt-determinations between several 

 methods, each of which has in turn been extensively 

 adopted. The most simple process, is first to evaporate the 

 water, and then dry and weigh the salts left in the residue, 

 a mode of operation which. though lea ding direct to the 

 desired result. involves considerable labour. Two other 

 methods. not so direct. but far less tedious. consist . in 

 determining either the specific gravity of the water or the 

 amoimt of chlorine 1 it contains. from which. by means of 

 proper coefficients. the total amoimt of salt may be.com- 

 puted, provided always that a constant proportion can be 

 assunied to exist between the solid constituents of sea-water. 

 The first process is attended. irrespective of the trouble- 

 some mode of • operation, with another drawback, viz. the 

 impractibility of adopting it on board ship in the open 

 sea. where the motion of the vessel altogether precludes the 

 use of the balance. whereas both specific gravity determinations, 

 with the hydrometer, and volumetric determinations of 

 chlorine. may be performed at sea with the greatest ease, 

 and very considerable accuracy. even in comparatively rough 

 weather. 



Hence, when there is reason to fear that the samples 

 of water cannot be preserved for any length of time with- 

 out exposing them to chemical change. which might exert 

 a disturbing iufluence on the results; andwhenever, accord- 

 ingly. weight must be chietiy attached to their immediate 

 examination. the only practicable standard of measurement 

 for computing the total amoimt of salt will be that fumished. 

 by determinations of chlorine. or of specific gravity. 



On the first voyage of the Norwegian Exprdition, 

 Svendsen, who then. as .previously stated. did the chemical 



1 By "the amcnml of chlorine," here and elsewliere throughoul 

 this Memoir, i^ understood the total amoual of chlorine and bromine. 



