Epsom Salt (Magnesium Sulphate): Uses and Safety

Epsom salt is magnesium sulphate heptahydrate, a hydrated magnesium salt named after the English town of Epsom, where it was first found in spring water. It looks like coarse table salt but is chemically very different. It is not sendha namak (rock salt), which is sodium chloride.

• Formula: MgSO4·7H2O
• CAS number: 10034-99-8 (heptahydrate); 7487-88-9 is the anhydrous form
• Molar mass: about 246.5 g/mol
• Appearance: colourless or white crystals, odourless, with a bitter taste
• Solubility: very soluble, about 113 g per 100 mL of water at 20 °C

When heated, it gives up its water of crystallisation and becomes a dry white powder. Left open in humid air, the crystals slowly clump together. Dissolved in water, it gives a roughly neutral solution, so it doesn't behave like an alkali or an acid.

Azlok lists Epsom salt in two forms:

Neither is sold as food or pharmacopoeia grade. Check today's price per kg for both packs.

• Bath and foot soaks: dissolved in warm water for a relaxing soak, often blended with essential oils or fragrance into bath salts.
• Gardening: a source of magnesium and sulphur for plants grown in magnesium-poor soil. Gardeners use it on roses, tomatoes, chillies and potted plants showing yellowing between leaf veins.
• Craft and school projects: grows fine needle crystals on glass or paper when a saturated solution evaporates.
• Cosmetics: an ingredient in bath salts, scrubs and some hair products.
• Industry and lab: used in textile finishing, fertiliser blends, and, in dried anhydrous form, as a drying agent for organic solvents.

1. Bath soak: bath-salt packs commonly suggest about 1 to 2 cups (roughly 250–500 g) in a full bathtub of warm water. Stir until dissolved and soak for 15–20 minutes.
2. Bucket bath or foot soak: about half a cup (around 100 g) in a bucket or tub of warm water is a common amount.
3. Plants: gardeners commonly dissolve 1 tablespoon (about 15 g) in 4 litres of water and use it as a monthly drench or leaf spray. Get a soil test if leaves stay yellow, as the cause may not be magnesium.
4. Crystal growing: dissolve Epsom salt in hot water until no more dissolves, pour into a shallow dish, and leave it in a cool place overnight.
5. DIY bath salts: mix the crystals with a few drops of fragrance oil and a little baking soda, and store in a closed jar.

Do a patch test with any new bath blend, especially if you have sensitive skin.

• Epsom salt is meant for external use only. Don't eat it or put it in food or drinks.
• Keep it away from eyes. If it gets in, rinse with clean water for a few minutes.
• Stop using a bath blend if your skin gets red or itchy.
• Don't over-apply in the garden. Too much salt in pots can burn roots and leaf edges.
• Store it in a sealed container in a dry place. It cakes if left open in humid weather.
• Label the jar clearly so nobody confuses it with table salt or sendha namak.
• Keep it out of reach of children and pets.
• Small amounts dissolved in water can go down the drain.

For baths, foot soaks and gardening, the 1 kg bath salt pack gives you more for regular use. If you're making bath salts, scrubs or other products to sell, the 450 g cosmetic raw ingredient listing is the better starting point. Finished cosmetics sold in India have to meet CDSCO and BIS requirements, so keep supplier documents ready.

Nurseries, spa suppliers and bath product makers needing 25 kg or more can ask for a quote through bulk inquiry.