The alchemical bath — variously designated balneum, bain marie, Mary’s Bath, or the mercurial font — occupies a central position in the depth-psychological reception of alchemy as a symbol of dissolution, purification, and transformative immersion. Across the corpus, the term carries a dual valence: it is simultaneously a physical apparatus (the water-jacket heating method, the bain marie) and a charged symbolic operation in which opposing principles — Sol and Luna, king and queen, sulphur and argent vive — enter a shared medium and are dissolved into one another. Jung’s sustained engagement with the Rosarium Philosophorum woodcuts in ‘The Psychology of the Transference’ (CW 16) established the paradigmatic depth-psychological reading: the bath in which the royal pair submerge enacts the coniunctio, imaging the unconscious intermingling of analyst and analysand. Edinger extends this into a systematic typology of solutio, tracing the bath’s double action — dissolution of old form, emergence of regenerated form — through clinical dream material. Hillman, characteristically, attends to the technical ingenuity of the bain marie itself, reading it as an image of productive indirection: fire and water brought into cooperation without either element touching the substance. Abraham’s lexicographical work grounds all these psychological readings in the primary textual tradition, showing the bath to be synonymous with the dunghill, the horse-belly, and the mercurial secret fire — a network of identifications that reveals how the bath is not merely a vessel but the very medium of transformation.