Washing soda is sodium carbonate. NOT sodium bicarbonate which is baking soda. In some areas/stores you can find washing soda in your laundry aisle. If you can't find it in your laundry aisle...it is also used as PH balancer for pools. It is PHplus. Just look at the ingredients. It should be the only one.
http://www.soapsgonebuy.com/ProductDetails.asp?ProductCode=AH1001&Show=ExtInfo
I have been making my own powder detergent for around 2 years now. I spend less than $20 a YEAR. The powder takes only about 2 minutes to make. I never notice I am low until I go to do a load and there isn't any detergent. Here is my recipe:
1 cup borax
1 cup washing soda
1/2 cup laundry booster (Oxy Clean or Sun and the like)
I notice your recipe for the dry powder doesn't include Fels Naptha or Ivory....or did you forget to type that ingredient?? thanks