The percipitate is calcium salts that have been forced out of the water by the more soluble S. Sulfite and S. Carbonate.
Adding EDTA or Calgon runs a small risk of changing the pH. I suggest using DiSodium EDTA to minimize this risk and also because it is more common than EDTA itself. Use about 5 grams in 1 liter.
PE
*******The usual calcium hardness is due to calcium hydroxide which is somewhat soluble in water. If you breathe through a soda straw into such hard water, the CO2 in your breath will combine with calcium hydroxide to make calcium carbonate and water. That is limestone, which precipitates.
Ron,
EDTA is commonly available as both Di-Sodim and Tetra-Sodium. As I recall, the Di version is acidic, the Tetra version alkaline. Thus, both can change the pH of any stock or working solution.
What do you mean by the common form of EDTA? Is this the Tetra version?
Sandy
*******
So could that be filtered and used?
A gram or two per liter of sodium hexametaphosphate added to the water before dissolving the main components should help to prevent this from happening. http://www.dharmatrading.com/ws.html
It is mentioned in Grant Haist`s Modern Photographic Processing (Volume 1) that ORIGINAL CALGON was a polymeric form of sodium hexametaphosphate and was sold under the name trade name of CALGON, but care must be taken that the product contains only sodium hexametaphosphate. The following page goes on to say that "CALGON is said to be the best sequestering agent of the phosphates, but it`s use is limited by it`s tendency to take up water, becoming sticky and hydrolysing. CALGON therefore should not be kept in contact with the sulfite or the alkali of a developer for any length of time before the solution is mixed."That is the old and famous Calgon in the US. Hexametaphosphate is banned in some areas due to supposed environmental damage. I recommend this approach and can see little if any damage from use by photographers, but it might cause them trouble if this is one of the chemicals banned in their area.
It can cause algal blooms in streams and lakes and has a huge BOD due to the algae that grow. It was once used in most dishwashers and water softeners but is now rather hard to get.
An alternative is Dequest 2010 or one from that family.
PE
I have not had any problems with D-76/ID-11 with sodium hexametaphosphate added.Keith
Calgon was indeed mixed with some of the powder developers of the 60s.
PE
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