MadSci Network: Chemistry

Re: What causes a precipitate in our water?

Date: Sun May 21 23:33:14 2000
Posted By: Bonnie Tam, Research technician
Area of science: Chemistry
ID: 956380459.Ch

Hi Vic!

Water is hard because it has a lot of calcium or magnesium dissolved in it. Calcium and magnesium easily precipitate out of water and stick to the inside of pipes and metal containers. Water softeners replace calcium and magnesium ions with sodium ions. Sodium ions don't precipitate out of water so this "softens" the water.

Usually, water is run through a bed of beads or zeolite that is covered with sodium ions. As the water flows by, the ions exchange places so the beads or zeolite will contain the calcium and magnesium ions while sodium will be in the water.

To regenerate the beads, wash them with salt water so calcium and magnesium will go down the drain.

There are 2 types of water softeners: precipitating and non-precipitating. This salesman must have been selling you the precipitating variety. They include washing soda and borax. This forms an insoluble precipitate with calcium and magnesium ions which can damage surfaces and increase the alkalinity of the water. Non-precipitating softeners use complex phosphates to sequester ions and do not form deposits. I got this info from the following web site: Hard water

Good luck with your water softener!



Admin note:
Kai Bester adds the following:

Dear VIC it could have been anything, ..... such occasions are not exactly based on sound science, are they.

So if this was sound science, and You were dealing with a water softener, It should have been something to make a precipitate from chalk (basically a solution of calcium carbonate). So two ways to do it: either form a precipitate with calcium (generally sulfate solutions should do a good job) or do a precipitate with carbonate (barium solutions should do a good job)

in the end barium is toxic, thus the other way should be preferred, but who knows.

At the days end, there are dozens of reasonable approaches to this thing, again only considering reasonable things have been done....

The best approach is to ask the manufactorer, if You are really interested.



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