The sulfer is not a book, but rather looks like a "chemist's herbs" mixing bowl, found in the citadel medical office along the back wall tables. You first mix the coal and salt, then put the coal-salt mixture with the sulfer. The key to get into the LavaControlRoom is in the last chamber where you meet Samual. After defeating the four Elite DK's that he leaves behind, you take the keys that they drop and open up locked rooms to the left and right of your screen. The key to the LavaControlRoom is in the room on the left. Take the Lava key back downstairs and bypass the regular exit, backtrack to the Lava Room. Kill the smithy, the imp will scream and run off if you try to talk to him. Take the explosives and place them on the lava flow just below the valve in the wall (it will highlight). You'll get experience points and a cut scene will immediately follow.
Ralph
