Quote Originally Posted by jnanian View Post
from what i understand borax can be replace sodium metaborate in some formulas even though it is sodium tetaborate
( in d-23 for example ) and i think ( correct me if i am wrong ) the film developing cookbook says this ..
The pH produced by sodium tetraborate (borax) and sodium metaborate (Kodalk) are quite different and one cannot be substituted for the other. Borax is a mild alkali while sodium metaborate is almost a alkaline as sodium carbonate. If the FDC says that they are interchangeable then this is another error in a poorly edited book. Borate chemistry is rather complex and the naming can be quite confusing.

Years ago I contacted US Borax about the purity of Twenty Mule Team borax. It is more than pure enough for photo purposes. The principle impurity is a very small amount of sodium chloride.