Triple Point (chemicals.triple)

This module contains lookup functions for a chemical’s triple temperature and pressure. The triple temperature is the unique co-existence point between a pure chemicals’s solid, gas, and liquid state.

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Triple Temperature

chemicals.triple.Tt(CASRN, method=None)[source]

This function handles the retrieval of a chemical’s triple temperature. Lookup is based on CASRNs. Will automatically select a data source to use if no method is provided; returns None if the data is not available.

Returns data from [1], [2] or [3], or a chemical’s melting point if available.

Parameters:
CASRNstr

CASRN [-]

Returns:
Ttfloat

Triple point temperature, [K].

Other Parameters:
methodstr, optional

A string for the method name to use, as defined in the variable, Tt_all_methods.

See also

Tt_methods

Notes

Median difference between melting points and triple points is 0.02 K. Accordingly, this should be more than good enough for engineering applications.

The data in [1] is originally on the ITS-68 temperature scale, but was converted to ITS-90. The numbers were rounded to 6 decimal places arbitrarily and the conversion was performed with this library.

References

[1] (1,2)

Staveley, L. A. K., L. Q. Lobo, and J. C. G. Calado. “Triple-Points of Low Melting Substances and Their Use in Cryogenic Work.” Cryogenics 21, no. 3 (March 1981): 131-144. doi:10.1016/0011-2275(81)90264-2.

[2]

Shen, V.K., Siderius, D.W., Krekelberg, W.P., and Hatch, H.W., Eds., NIST WebBook, NIST, http://doi.org/10.18434/T4M88Q

[3]

Huber, Marcia L., Eric W. Lemmon, Ian H. Bell, and Mark O. McLinden. “The NIST REFPROP Database for Highly Accurate Properties of Industrially Important Fluids.” Industrial & Engineering Chemistry Research 61, no. 42 (October 26, 2022): 15449-72. https://doi.org/10.1021/acs.iecr.2c01427.

Examples

Ammonia

>>> Tt('7664-41-7')
195.49
chemicals.triple.Tt_methods(CASRN: str) → list[str][source]

Return all methods available to obtain the triple temperature for the desired chemical.

Parameters:
CASRNstr

CASRN, [-]

Returns:
methodslist[str]

Methods which can be used to obtain the Tt with the given inputs.

See also

Tt
chemicals.triple.Tt_all_methods = ('HEOS', 'STAVELEY', 'WEBBOOK', 'MELTING')

Tuple of method name keys. See the Tt for the actual references

Triple Pressure

chemicals.triple.Pt(CASRN, method=None)[source]

This function handles the retrieval of a chemical’s triple pressure. Lookup is based on CASRNs. Will automatically select a data source to use if no method is provided; returns None if the data is not available.

Returns data from [1], [2], or [3].

This function does not implement it but it is also possible to calculate the vapor pressure at the triple temperature from a vapor pressure correlation, if data is available; note most Antoine-type correlations do not extrapolate well to this low of a pressure.

Parameters:
CASRNstr

CASRN [-]

Returns:
Ptfloat

Triple point pressure, [Pa]

Other Parameters:
methodstr, optional

A string for the method name to use, as defined in the variable, Pt_all_methods.

See also

Pt_methods

References

[1]

Staveley, L. A. K., L. Q. Lobo, and J. C. G. Calado. “Triple-Points of Low Melting Substances and Their Use in Cryogenic Work.” Cryogenics 21, no. 3 (March 1981): 131-144. doi:10.1016/0011-2275(81)90264-2.

[2]

Shen, V.K., Siderius, D.W., Krekelberg, W.P., and Hatch, H.W., Eds., NIST WebBook, NIST, http://doi.org/10.18434/T4M88Q

[3]

Huber, Marcia L., Eric W. Lemmon, Ian H. Bell, and Mark O. McLinden. “The NIST REFPROP Database for Highly Accurate Properties of Industrially Important Fluids.” Industrial & Engineering Chemistry Research 61, no. 42 (October 26, 2022): 15449-72. https://doi.org/10.1021/acs.iecr.2c01427.

Examples

Ammonia

>>> Pt('7664-41-7')
6053.386
chemicals.triple.Pt_methods(CASRN: str) → list[str][source]

Return all methods available to obtain the Pt for the desired chemical.

Parameters:
CASRNstr

CASRN, [-]

Returns:
methodslist[str]

Methods which can be used to obtain the Pt with the given inputs.

See also

Pt
chemicals.triple.Pt_all_methods = ('HEOS', 'STAVELEY', 'WEBBOOK')

Tuple of method name keys. See the Pt for the actual references