Iron Hydroxide : A brown, gelatinous precipitate that comes out of a spent acid solution when the acid spends completely or when the Ferrous Iron (+2) in solution at pH > 1.8 oxidizes to Ferric iron (+3)
George E. King Engineering, 5000 Oilfield Terms: A Glossary of Petroleum Engineering Terms, Abbreviations and Acronyms, US 2010. http://gekengineering.com/Downloads/Free_Downloads /Glossary_of_Petroleum_Engineering_Terms_25_August _2010.pdf, (Oil - Amer) {593}