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The subject of this article appears in The Maze of Bones.

Iron Solute is one of the 39 Clues that make up Gideon Cahill's master serum. To unlock this clue, one must add the 6 cards from The Maze of Bones.


Amy and Dan Cahill discovered that the piece of paper Grace Cahill gave them has the Clue after all. RESOLUTION was the answer to the missing word. Dan solved the anagram, discovering the clue IRON SOLUTE.


The Cutscene shows exactly the same paper that was given to Dan and Amy. The letters in the RESOLUTION go out and go in another place and forms the word Iron Solute.


The key on the cards that form the card combo for this Clue contains a bone.

Card Combo[]

Card1 Card2 Card3 Card4 Card5 Card6

About Iron Solute[]

Iron solute is used for many things. It can be used for metalworking and chemistry.

For a historical perspective, it is likely simply iron (II) ions within an aqueous medium. The book mentions that iron solute is used in printer ink. Since iron solute does not exist within chemistry, the next best thing is analyzing what is used to make said ink. In this case, it is usually made with iron (II) sulfate dissolved in a solution of tannic acid.


  • In the book, Amy says it is an ingredient for ink.
  • "Solute" means "dissolved in water" so "Iron solute" can be written Fe(II) (aq) or Fe(III) (aq). Fe (aq) unfortunately does not exist since metals are insoluble in water.
  • Grace Cahill wrote RESOLUTION as an anagram to it.

    The Iron Solute Symbol

Iron Ore

Iron before it is liquified into Iron Solute


The 39 Clues Clue 18