Disodium malonate is an ionic sodium salt that is soluble in water. Naphthalene is a molecular covalent organic solid that is insoluble in water. To purify, add the mixture to water and stir to dissolve the disodium malonate and then filter. The insoluble naphthalene residue will be trapped in the filter paper, while the pure disodium malonate can be recovered by evaporating the filtrate. Solution Disodium malonate is an ionic sodium salt that is soluble in water. Naphthalene is a molecular covalent organic solid that is insoluble in water. To purify, add the mixture to water and stir to dissolve the disodium malonate and then filter. The insoluble naphthalene residue will be trapped in the filter paper, while the pure disodium malonate can be recovered by evaporating the filtrate..