In chemistry, refers to ionic compounds like sodium chloride, calcium sulfate, etc. Not used for table salt in everyday contexts (that is しお).
化学の実験で、塩を水に溶かした。
In the chemistry experiment, we dissolved the salt in water.
When hydrochloric acid reacts with sodium hydroxide, a salt is formed.
The 塩 in 塩化ナトリウム (sodium chloride) indicates chloride.
塩(えん) is the chemistry term for any ionic salt compound, while しお (also written 塩) means everyday table salt or sea salt.
salt; salt content
chlorine (Cl)
chloridation; salification · chloride
base
hydrochloric acid
The kanji 塩 means 'salt'. The reading えん is the on'yomi, used in technical and compound contexts.
nitrate
salts
salt making; salt production
low-salt; low-sodium
salting; adding salt; containing salt
PVC; polyvinyl chloride
salt well; brine well
salt and miso · salt and vinegar · everyday food; simple fare
ammonium chloride
salting and drying
saline; halophytic
salting out
seasoning; flavor · serving one's lord well