The density and expansibility of artificial seawater solutions from 0 to 40°C and 0 to 21‰ chlorinity

Frank J. Millero, Fred K. Lepple

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Abstract

The density of artificial seawater has been measured with a magnetic float densitometer at 1 atm. from 0 to 40°C (in 5° intervals) and from 0 to 21‰ chlorinity. The densities at each temperature have been fitted to a modified Root (1933) equation, d = d0 + AV′ ClV + BV′ ClV 3 2 and an equation based on the Debye-Hückel limiting law, d = d0 + AV ClV + BV ClV 3 2 + CV ClV2 where AV′, BV′, AV, BV and CV are temperature-dependent constants (related to the ion-water and ion-ion interactions of the major components), d0 is the density of pure water and ClV is the volume chlorinity - ClV = Cl (‰) × density. The densities fit these equations to ±9 p.p.m. from 0 to 25°C and ±18 p.p.m. from 30 to 40°C. The densities for artificial seawater are in good agreement with our measurements of Copenhagen seawater and the results for natural seawater obtained from Knudsen's tables. The expansibilities of the artificial seawater mixtures have been calculated from the temperature dependence of the densities. The resulting expansibilities at each temperature were fitted to the equations α = α0 + AE′ ClV + BE′ ClV 3 2 and α = α0 + AE ClV + BE ClV 3 2 + CE ClV2 where AE′, BE′, AE, BE and CE are constants (related to the effect of temperature on the ion-water and ion-ion interactions of the major components) and α0 is the expansibility of pure water. The expansibilities fit these equations to ±1 p.p.m. and at 35‰ S agree within ±1 p.p.m. with the expansibilities obtained for natural seawater from Knudsen's tables. Theoretical density and expansibility constants have been determined from the apparent equivalent volumes and expansibilities of the major components of seawater by using the additivity principle. The average deviations of the calculated densities and expansibilities are, respectively, ±20 and ±3 p.p.m. over the entire temperature range.

Original languageEnglish (US)
Pages (from-to)89-104
Number of pages16
JournalMarine Chemistry
Volume1
Issue number2
DOIs
StatePublished - Apr 1973

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ASJC Scopus subject areas

  • Oceanography
  • Chemistry(all)
  • Environmental Chemistry
  • Water Science and Technology

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