# EPA On-line Tools for Site Assessment Calculation

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Data for MTBE were selected from Fischer et al. (2004)^{1}. These data were used to approximate the van't Hoff relationship for MTBE by fitting a linear regression through the ln K_{h} versus the inverse temperature, T_{K} in Kelvin (273 K = 0 ^{o}C), plot. The regression equation was ln K_{h} = -4256.2 (1/T_{K}) + 6.927 for K_{h} in units of atm - m^{3} / mol. As a measure of the fit of the equation to the data, the R^{2} was 0.9729.

After fitting the relationship, the original data (triangles) were plotted against the estimates (curve). (The estimates follow a curve, because the linear regression was taken in the log space.)

In absolute terms, the errors in the estimates were found to range from 0 to 14.5% as shown in the following table and graph.

Temperature ^{o}C |
% Error in Henry's Constant Estimate |
---|---|

3 | 0.549451 |

5 | -8.9285 |

10 | 14.5299 |

15 | -1.69492 |

20 | 0 |

25 | -2.39726 |

#### References

^{1}Fischer, A., M. Muller, J. Klasmeier, 2004, Determination of Henry's law constant for mthyl *tert*-butyl ether (MTBE) at groundwater temperatures, Chemosphere, 54, 689-694.

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