"esprit de sel" meaning in French

{
  "forms": [
    {
      "form": "esprits de sel",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "m",
        "2": "-",
        "3": "+"
      },
      "expansion": "esprit de sel m (usually uncountable, plural esprits de sel)",
      "name": "fr-noun"
    }
  ],
  "lang": "French",
  "lang_code": "fr",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "French entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "spirit of salt, spirits of salts (a name for hydrochloric acid, not now generally used in chemistry but still used in some commercial and domestic labelling)"
      ],
      "id": "en-esprit_de_sel-fr-noun-1YERgwLD",
      "links": [
        [
          "spirit of salt",
          "spirit of salt"
        ],
        [
          "spirits of salts",
          "spirits of salts"
        ],
        [
          "hydrochloric acid",
          "hydrochloric acid#English"
        ]
      ],
      "synonyms": [
        {
          "word": "acide chlorhydrique"
        }
      ],
      "tags": [
        "masculine",
        "uncountable",
        "usually"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ɛs.pʁi d(ə) sɛl/"
    }
  ],
  "word": "esprit de sel"
}

{
  "forms": [
    {
      "form": "esprits de sel",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {
        "1": "m",
        "2": "-",
        "3": "+"
      },
      "expansion": "esprit de sel m (usually uncountable, plural esprits de sel)",
      "name": "fr-noun"
    }
  ],
  "lang": "French",
  "lang_code": "fr",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "French countable nouns",
        "French entries with incorrect language header",
        "French lemmas",
        "French masculine nouns",
        "French multiword terms",
        "French nouns",
        "French nouns with red links in their headword lines",
        "French terms with IPA pronunciation",
        "French uncountable nouns"
      ],
      "glosses": [
        "spirit of salt, spirits of salts (a name for hydrochloric acid, not now generally used in chemistry but still used in some commercial and domestic labelling)"
      ],
      "links": [
        [
          "spirit of salt",
          "spirit of salt"
        ],
        [
          "spirits of salts",
          "spirits of salts"
        ],
        [
          "hydrochloric acid",
          "hydrochloric acid#English"
        ]
      ],
      "synonyms": [
        {
          "word": "acide chlorhydrique"
        }
      ],
      "tags": [
        "masculine",
        "uncountable",
        "usually"
      ]
    }
  ],
  "sounds": [
    {
      "ipa": "/ɛs.pʁi d(ə) sɛl/"
    }
  ],
  "word": "esprit de sel"
}