from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A hydrate whose solid contains seven molecules of water of crystallization per molecule, or per unit cell
from The Century Dictionary and Cyclopedia
- n. In chem., a compound containing seven molecules of water, as common copperas in crystals, or ferrous sulphate heptahydrate (FeSO4.7H2O).
 Green vitriol, ferrous sulphate heptahydrate, a compound of iron, sulphur, and oxygen, crystallised with seven molecules of water, represented by the formula FeSO4.
Green vitriol is a heptahydrate of iron (II) sulfate or ferrous sulfate.
Another struggles with the simple inorganic salts required to make up buffer solutions, ortho, dihydrate, heptahydrate, anhydrous.
Sodium carbonate has three known forms of hydrates: sodium carbonate decahydrate (natron), sodium carbonate heptahydrate (not known in mineral form) and sodium carbonate monohydrate (mineral thermonatrite).
It most commonly occurs as a crystalline heptahydrate which readily effloresces to form a white powder, the monohydrate.
A stock solution of trace elements was prepared that contained the following (in mg/l): Zinc sulphate (heptahydrate), 143.77; Magnesium chloride