### Abstract

The density and compressibility of seawater salt solutions for ionic strengths 0 to 0.8 m, temperatures 0-40°C, and applied pressure 0 to 1000 bar are fitted to the Pitzer equations. The apparent molal volumes and compressibilities (Xφ) are fitted to equations of the form Xφ = X̄^{0} + A_{X}II(1.2 m) In(I + 1.2 I^{0.5}) + 2 RT m(β^{(0)X} + β^{(1)X}g(y) + m C^{X}) where I is the ionic strength, m is the molality of sea salt, A_{X} is the Debye-Hückel slope for the volume (X = V) or compressibility (X = κ) and g(y) = (2/y^{2}) [1 - (1 + y)exp(x)] where y = 2 I^{0.5}. The Pitzer parameters β^{(0)X}, β^{(1)X}, and C^{X} are fitted to functions of temperature and pressure in the form Y^{X} = Σ_{i} Σ_{j} a_{ij}(T - T_{R})^{ipj} where a_{ij} are adjustable parameters, Y^{X} is the Pitzer parameter, T is the temperature in K, T_{R} = 298.15 K, and P is the applied pressure in bars (P = 0 at 1 atm or 1.013 bar). The standard deviations of the seawater fits are 8.3×10^{-6} cm^{3}-g^{-1} for the specific volumes, 0.0007×10^{-6} bar^{-1} for the compressibilities, and 0.63×10^{-6} K^{-1} for the thermal expansibilities. At 25°C, the measured densities of seawater are compared to the calculated values using Pitzer coefficients for the major sea salts. The results agree with the measured values to within 45 ×10^{-6} g-cm^{-3}.

Original language | English (US) |
---|---|

Pages (from-to) | 719-742 |

Number of pages | 24 |

Journal | Journal of Solution Chemistry |

Volume | 29 |

Issue number | 8 |

State | Published - Aug 2000 |

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### Keywords

- Apparent molal volumes
- Apparent molar compressibilities
- Pitzer equations
- Sea salts
- Seawater

### ASJC Scopus subject areas

- Physical and Theoretical Chemistry

### Cite this

*Journal of Solution Chemistry*,

*29*(8), 719-742.

**The apparent molal volume and compressibility of seawater fit to the Pitzer equations.** / Pierrot, Denis; Millero, Frank J.

Research output: Contribution to journal › Article

*Journal of Solution Chemistry*, vol. 29, no. 8, pp. 719-742.

}

TY - JOUR

T1 - The apparent molal volume and compressibility of seawater fit to the Pitzer equations

AU - Pierrot, Denis

AU - Millero, Frank J

PY - 2000/8

Y1 - 2000/8

N2 - The density and compressibility of seawater salt solutions for ionic strengths 0 to 0.8 m, temperatures 0-40°C, and applied pressure 0 to 1000 bar are fitted to the Pitzer equations. The apparent molal volumes and compressibilities (Xφ) are fitted to equations of the form Xφ = X̄0 + AXII(1.2 m) In(I + 1.2 I0.5) + 2 RT m(β(0)X + β(1)Xg(y) + m CX) where I is the ionic strength, m is the molality of sea salt, AX is the Debye-Hückel slope for the volume (X = V) or compressibility (X = κ) and g(y) = (2/y2) [1 - (1 + y)exp(x)] where y = 2 I0.5. The Pitzer parameters β(0)X, β(1)X, and CX are fitted to functions of temperature and pressure in the form YX = Σi Σj aij(T - TR)ipj where aij are adjustable parameters, YX is the Pitzer parameter, T is the temperature in K, TR = 298.15 K, and P is the applied pressure in bars (P = 0 at 1 atm or 1.013 bar). The standard deviations of the seawater fits are 8.3×10-6 cm3-g-1 for the specific volumes, 0.0007×10-6 bar-1 for the compressibilities, and 0.63×10-6 K-1 for the thermal expansibilities. At 25°C, the measured densities of seawater are compared to the calculated values using Pitzer coefficients for the major sea salts. The results agree with the measured values to within 45 ×10-6 g-cm-3.

AB - The density and compressibility of seawater salt solutions for ionic strengths 0 to 0.8 m, temperatures 0-40°C, and applied pressure 0 to 1000 bar are fitted to the Pitzer equations. The apparent molal volumes and compressibilities (Xφ) are fitted to equations of the form Xφ = X̄0 + AXII(1.2 m) In(I + 1.2 I0.5) + 2 RT m(β(0)X + β(1)Xg(y) + m CX) where I is the ionic strength, m is the molality of sea salt, AX is the Debye-Hückel slope for the volume (X = V) or compressibility (X = κ) and g(y) = (2/y2) [1 - (1 + y)exp(x)] where y = 2 I0.5. The Pitzer parameters β(0)X, β(1)X, and CX are fitted to functions of temperature and pressure in the form YX = Σi Σj aij(T - TR)ipj where aij are adjustable parameters, YX is the Pitzer parameter, T is the temperature in K, TR = 298.15 K, and P is the applied pressure in bars (P = 0 at 1 atm or 1.013 bar). The standard deviations of the seawater fits are 8.3×10-6 cm3-g-1 for the specific volumes, 0.0007×10-6 bar-1 for the compressibilities, and 0.63×10-6 K-1 for the thermal expansibilities. At 25°C, the measured densities of seawater are compared to the calculated values using Pitzer coefficients for the major sea salts. The results agree with the measured values to within 45 ×10-6 g-cm-3.

KW - Apparent molal volumes

KW - Apparent molar compressibilities

KW - Pitzer equations

KW - Sea salts

KW - Seawater

UR - http://www.scopus.com/inward/record.url?scp=0034349190&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0034349190&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0034349190

VL - 29

SP - 719

EP - 742

JO - Journal of Solution Chemistry

JF - Journal of Solution Chemistry

SN - 0095-9782

IS - 8

ER -