How does Shakespeare use language to portray Iago's character in Othello?

The language Shakespeare uses differs largely when Iago is on stage with other characters and when he is on stage alone. Around other characters, his language is refined and sophisticated, and he mostly speaks in verse. However, when he is on stage alone and speaks only to the audience (this device is called a "soliloquy" and is frequently employed by Shakespeare in order to give the audience an insight into the character's inner thoughts), his language differs greatly. It is much more derogatory (e.g., he calls Othello an "old black ram", but when Othello is present, he shamelessly declares: "my Lord, you know I love you"). In the soliloquies, it is also not uncommon that Iago speaks in prose rather than in verse, which, in Shakespeare's day, was considered to be of lower status and thus may indicate that the character speaking in prose is not as "noble" as those speaking in verse. This contrast in the language Shakespeare employs for Iago thus represents the ambivalent nature of his character.