What literary devices are used in Macbeth, Act 5, Scene 1?
In her somnambulant ravings, Lady Macbeth employs hyperbole (or overstatement) when she says that "All / the perfumes of Arabia will not sweeten this little / hand" (5.1.53-55). It is sure that, had she all the perfumes in the Arab world, they would certainly cover up the smell of blood she still seems to detect on her hands. By employing this hyperbole, however, Shakespeare lets us know just how incredibly guilty she feels as a result of this metaphorical blood on her hands. It is not the blood she cannot wash off; the blood is gone. It is her guilt that stays with her.
The doctor uses metonymy, a substitution of one thing for something that it is connected with, when he says that Lady Macbeth's "heart is sorely / charged" (5.1. 56-57). He connects her heart with her emotions; her heart is no different than it ever was physically, but her emotions and her conscience are heavily weighted by the things that she has seen and known.
Likewise, the gentlewoman employs metonymy when she says, "I would not have such a heart in my / bosom for the dignity of the whole body" (5.1.58-59). It is not Lady Macbeth's body that has dignity; it is her position as the queen to which her serving woman is referring. She means that she would not sacrifice her clean conscience and unburdened heart (again, metonymy) even if it meant that she could possess her mistress's power and authority. Such a trade-off would not be worth it.
Further, the doctor personifies pillows when he says that "Infected minds / To their deaf pillows will discharge their secrets" (5.1.76-77). We wouldn't typically say that pillows are "deaf" because they are objects and not living beings. He also uses a metaphor to describe guilt as an infection, something physical that can cause decay and rot, just as guilt is felt to do. Further, when he says "Infected minds," he really means "Guilty people," and so "minds," again, is a metonymy for people.