The Handyman's Pocket Book: Carpet Shampoo.

Shred 2 oz. of white soap into a pint of boiling water and leave to dissolve.  Add 1 oz. methylated spirits, 1 tablespoonful of ammonia (.880) (P), and a piece of washing soda about the size of a walnut.  Bottle, and shake before use.  Apply with a soft scrubbing brush and sponge off with clear warm water.  Leave windows open to help dry out quickly.