Possible Clues:

• There's something a little lousy about the salt, Peter
• Is that what's so lousy about what's in gunpowder?
• Gunpowder has to to make it more dark, perhaps, by the sound of it
• That's a little lousy about what's in gunpowder
• Unusual ecstasy to demonstrate in spectacle
• Explosive ingredient hidden by close-knit relatives
• Salt peter
• Name 'sex appeal' with reference to explosive ingredient
• Egg about to be served with salt
• Potassium nitrate or saltpetre