deliquesce

To melt by absorbing water and disappearing.

But I could find no saltpetre; indeed, no nitrates of any kind. Doubtless they had deliquesced ages ago.

The buildings were Victorian ruins; there were never any razor blades; cheap socks deliquesced beneath your feet.

To become liquid by absorbing water from the atmosphere and dissolving in it.

Some salts will deliquesce when left exposed.