Quote Originally Posted by Photo Engineer View Post
I have refrained from posting in this thread until now. I feel that I have to clarify my position as well.

Kirk not only has his chemistry straight, he has also stated in this quoted post my own thoughts on this matter.

The most common impurities are halide salts and insoluable colloidal salts. Patrick has alluded to the latter in the past saying that some of his Borax solutions are cloudy and the cloudy suspension cannot be filtered out.


PE
The very first thing I did was to prepare a nearly saturated solution of borax in very hot water. After cooling, most of the borax had settled out, leaving only about 47 grams/liter in solution along with most of the soluble and colloidally suspended impurities. Decanting the solution thus removed most of the soluble impurities. There is no point in trying to filter out any impurities, be they truly dissolved or colloidally suspended, if they can be decanted at the cost of only a few percent of the original amount of borax. Furthermore, even the best grade of borax is likely to be a mixture of pentahydrate and decahydrate, so in any case where an accurate assay of Na2B4O7 is required, the standard procedure is to prepare a saturated solution. This solution, if kept at a temperature above that of its formation, will have a known borax content expressed as weight percent of the decahydrate. Thus, a saturated solution formed at 20 C will contain 4.71% sodium tetraborate decahydrate, or 47.1 grams per liter.

I think you will see if you look at my developers, that I have for many years spent most of my effort designing sulfite-free developers. The major thing I have against sulfite is cost and local avilability. It is often the most expensive component, and among the hardest to get. Anyway, it's part of my fun to see what I can do with what I can get in the middle of Wild and Wonderful West Virginia.