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To determine whether Hydrogen chloride (HCl) is polar or nonpolar, the decisive question is whether the bond dipoles of the molecule cancel once its three-dimensional shape is taken into account. Hydrogen chloride is an inorganic compound. As set out in the HCl Lewis Structure Guide, HCl has 1 heavy atom. Hydrochloric acid is used in the production of chlorides, for refining ore in the production of tin and tantalum, for pickling and cleaning of metal products, in electroplating, in removing scale from boilers, for the….
The bond polarities follow from electronegativity. As a result, the literature gas-phase dipole moment is μ ≈ 1.08 D. Treated as a dilute ideal gas at 298 K and 1 atm, the Debye equation converts that dipole into a relative permittivity of about 1.00290 — a number very close to unity, which is exactly what a gas-phase value should look like.
For formulation and process work, the useful consequences are these: the calculated topological polar surface area is 0.0 Ų, 0 hydrogen-bond donors and 0 hydrogen-bond acceptors, the Crippen calculated partition coefficient is logP ≈ 0.42 and the calculated molar refractivity is 7.25 cm³ mol⁻¹. A logP in this range means the molecule is amphiphilic enough to cross between phases, which is often the useful behaviour in extraction and formulation. PubChem’s curated experimental record adds: Hydrogen chloride is 82.3 g/100 g at 32 °F (NTP, 1992).
PubChem’s use and manufacturing record describes Hydrogen chloride as follows: Hydrochloric acid is used in the production of chlorides, for refining ore in the production of tin and tantalum, for pickling and cleaning of metal products, in electroplating, in removing scale from boilers, for the neutralization of basic systems, as a laboratory reagent, as a catalyst and solvent in organic syntheses, in the… These applications are what make the polarity question practical — solvent choice, extraction recovery, cleaning and formulation all turn on how strongly the molecule interacts with polar phases.
The measured physical behaviour recorded for this substance is consistent with that picture. Solubility: 82.3 g/100 g at 32 °F (NTP, 1992). Physical Description: Hydrochloric acid, solution is a colorless watery liquid with a sharp, irritating odor.. Density: 1.05 at 59 °F for 10.17% weight/weight solution (EPA, 1998) - Denser than water;. Melting Point: -174.6 °F (Melting point is -13.7 °F for a 39.17% weight/weight solution.) (EPA, 1998). These are database values and should be read with the conditions (temperature, purity, pressure) that the source states.
Treated as a dilute gas, the calculated relative permittivity is about 1.00290 at 298 K and 1 atm. That figure is close to unity because a gas is mostly empty space: it is a useful consistency check on the dipole, but it is not the number to use when sizing a liquid process, where condensed-phase permittivity and specific interactions dominate.
The structure carries no strongly polar functional group, so the intermolecular forces are dominated by dispersion rather than by dipole–dipole attraction or hydrogen bonding.
PubChem’s GHS record for this substance lists H314: Causes severe skin burns and eye damage [Danger Skin corrosion/irritation] and H331: Toxic if inhaled [Danger Acute toxicity, inhalation]. Those classifications, not the polarity of the molecule, normally determine packaging, labelling, ventilation and transport requirements.
In short, specify Hydrogen chloride by assay, water content, impurity profile, packaging and transport class, and state the intended application on the enquiry. The polarity analysis above explains behaviour in use; it does not replace a specification.
The comparison below places HCl next to structurally related substances from the same catalogue. Dipole moments come from one consistent protocol (GFN2-xTB//MMFF94, gas phase, single conformer) and are quoted only where that protocol has been validated; where it has not, the cell says so instead of giving a number. Permittivities are dilute-gas estimates from the Debye equation, logP values are Crippen calculations, and the solubility column is a qualitative inference from the calculated descriptors rather than a measurement.
| Compound | Dipole Moment | Approx. Gas εr | log P / XlogP | Water Solubility Behavior | Industrial Sourcing |
|---|---|---|---|---|---|
| HCl | ≈1.08 D (lit.) | ≈1.0029 | logP ≈ 0.42 | 82.3 g/100 g at 32 °F (NTP, 1992) | See supply listing |
| ClCs | non-zero, not quoted | — | — | Dissolves by dissociation; ionic hydration dominates | See supply listing |
| CoCl2 | non-zero, not quoted | — | — | Dissolves by dissociation; ionic hydration dominates | See supply listing |
| KCl | non-zero, not quoted | — | — | Dissolves by dissociation; ionic hydration dominates | See supply listing |
| Cl | not applicable (element) | — | logP ≈ 0.69 | Moderate (inferred from logP) | See supply listing |
The spread across this table is the point: composition alone does not set the polarity verdict. HCl sits where it does because of the balance between weak dispersion forces and the asymmetry of its shape, and any of the neighbouring entries can be the better choice once the temperature, the phase and the required polarity window are fixed.
“A literature gas-phase dipole of about 1.08 D puts HCl in the moderate range. A calculated logP of 0.42 tells you where it will partition. The curated experimental record is consistent: 82.3 g/100 g at 32 °F (NTP, 1992).”
Regulatory status is specific to the substance and to the jurisdiction, and it changes. For CAS 7647-01-0 the authoritative public sources are the ECHA registered-substance database for the EU, and the OSHA and NIOSH tables for occupational exposure in the United States.
PubChem’s GHS record for this substance lists H314: Causes severe skin burns and eye damage [Danger Skin corrosion/irritation] and H331: Toxic if inhaled [Danger Acute toxicity, inhalation]. These statements are the ones that must appear on the label and in section 2 of the safety data sheet; they, rather than the polarity of the molecule, drive classification, packaging group and transport documentation.
No occupational exposure limit for this substance is quoted in this article, because none was present in the database record used here. Publishing a limit that is not on the record would be worse than publishing none: obtain the applicable value from the OSHA Z-table, the NIOSH pocket guide or the equivalent national instrument before designing the ventilation or monitoring programme.
From a compliance and sustainability standpoint, the polarity of HCl is a means rather than an end. It determines which solvent can replace another, how completely the substance can be recovered from a stream, and how much energy the separation will cost — so it belongs in the process justification, while the hazard classification and the exposure limits belong in the safety case.
A purchase enquiry for Hydrogen chloride (CAS 7647-01-0) should state the grade, assay basis, permitted impurity limits, water content, packaging, and the transport and regulatory status required for the destination market. Where the substance is used as a reagent or intermediate, the impurity profile usually matters more than the nominal percentage.
Because polarity governs phase behaviour, it also governs recovery: a moderate molecule is easier to strip from a non-polar stream and harder to dry than a non-polar one, and vice versa. Confirm the Guidechem supply listing for current availability and compare lots on the certificate of analysis rather than on the label alone.
Looking for commercial bulk supplies or technical documentation for Hydrogen chloride (CAS 7647-01-0)?
Hydrogen chloride is polar. The bond dipoles do not cancel, giving a literature gas-phase dipole of about 1.08 D.
The published gas-phase dipole is about 1.08 D. That literature value is quoted here rather than the calculation used elsewhere in this series, because the method is not validated for small inorganic species of this type.
Whether the individual bond dipoles cancel depends on how the bonds are arranged in three dimensions. Two identical bonds pointing in opposite directions cancel; the same two bonds at an angle do not.
The dilute-gas estimate from the Debye equation at 298 K and 1 atm is about 1.00290. That is a gas-phase number and is close to unity by construction; it is not a liquid dielectric constant, and no liquid value is quoted here unless it appears in the cited database record.
Not in routine tabulations. Snyder P′ was developed for conventional liquid chromatographic solvents, and this substance is outside the scope of that scale. Dipole moment, calculated logP and hydrogen-bond counts are the descriptors used here instead.
The curated database record states: 82.3 g/100 g at 32 °F (NTP, 1992). The calculated logP of 0.42 is consistent with that behaviour.
Grade, assay basis, water content, the declared impurity profile, packaging and the transport classification, plus the regulatory status required for the destination market. PubChem’s GHS record for this substance lists H314: Causes severe skin burns and eye damage [Danger Skin corrosion/irritation] and H331: Toxic if inhaled [Danger Acute toxicity, inhalation].
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