For an average washing load: Add 1/2 cup of baking soda to 1 cup of white distilled vinegar.
Pour the solution into the washing machine during the rinse cycle.
For a single garment: Place the yellowed or dingy garment into a sink filled with warm water. Add 1/2 cup of white distilled vinegar. Let the garment soak for up to one hour. Then wash as usual.
With lemon juice: Place the garment you want to whiten into a gallon of hot water. Use the bathroom sink or a bucket. Add 1/2 cup of lemon juice. Let the garment soak for 30 minutes or overnight if it is really yellow and dingy. Then wash as usual.