Hekla (Icelandic pronunciation: ()), or Hecla, is a stratovolcano in the south of Iceland with a height of 1,491 m (4,892 ft). Hekla is one of Iceland's most active volcanoes; over 20 eruptions have occurred in and around the volcano since 874.During the Middle Ages, the Icelandic Norse called the volcano the "Gateway to Hell".. Hekla is part of a volcanic ridge, 40 km (25 mi) long.

Oxalate (IUPAC: ethanedioate) is an anion with the formula C 2 O 4 2−.This dianion is colorless. It occurs naturally, including in some foods. It forms a variety of salts, for example sodium oxalate (Na 2 C 2 O 4), and several esters such as dimethyl oxalate (C 2 O 4 (CH 3) 2).It is a conjugate base of oxalic acid.At neutral pH in aqueous solution, oxalic acid converts completely to oxalate.