Some have succeeded in sculpturing Marble in very delicate designs by the aid of an acidulous liquor, which is formed by a mixture of spirits of salts and distilled vinegar.

https://web.archive.org/web/20060910002024/http://www.physchem.co.za/Acids/Introduction.htm
Acids which are commonly found in the laboratory are hydrochloric acid, HCl (still sometimes called by its ancient name spirits of salts), nitric acid, ...

Strong acid solutions (e.g. hydrochloric acid or "spirits of salts") are sometimes used to clean masonry and tiling of buildings but they should never be permitted to come into contact with metals, including stainless steel.

Spirits of salts

Meaning

Noun