The affix ṭhak meaning 'mixed therewith' is luk elided after the word lavaṇa,
Thus लवणेन संसृष्टः = लवणः 'mixed with salt' as लवणः सूपः 'soup mixed with salt.' So लवणं शाकं, लवणा यवगूः 1.1.51. The लूक् elision takes place when the word लवण is used as a noun, and not as an adjective.,