What kind of tone has been used by Ben Johnson in the play The Alchemist?

Generally there is a satirical tone to much of the alchemist. The prologue begins by addressing “Fortune,” wishing away the two hours that the play will take to perform and hoping to do justice to its author. It announces the play’s scene, London, with “no country’s mirth is better than our own.” It also is the best place to find whores and lowlifes. Many sorts of people, of many different humors, are to grace the stage. The writer, apparently, wishes not to attack these characters and the real people they represent, but to “better” them—the traditional aim of satire. 

The Alchemist is all about satire.

That means Jonson uses a boatload of humor, irony, and sarcasm to make fun of his characters and their flaws. (The play is chock-full of folks who are greedy, hypocritical, silly, and just plain foolish.)

Supposedly, the whole point of using a mocking tone is to improve society by exposing how ridiculous people can be. Basically, In The Alchemist, Jonson takes aim at London society in the early 1600's.