Look at this site for Doc Johnson's explanation.
http://www.koivet.com/html/articles/...h_term=dechlor
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RichToyBox
http://www.geocities.com/richtoybox/pondintro.html

"Bill Stock" wrote in message
...

"RichToyBox" wrote in message
...
My ST is clear looking cylindrical crystals. The instructions that came
with it was to mix it, 500 grams (slightly over a 1.1 pounds) with one
gallon of deionized water, and that would treat 18,000 plus gallons. I
use hose water, a postage scale to measure the ST, and make about 5 or 6
gallons at a time. I think that 1 ounce treats about 150 gallons of
water, and I generally use double or triple, because it is so cheap. I
bought a 50 pound bucket, around $60.

Sounds like the same stuff. It looks like elongated rock salt. But
according to my directions, 500 g (2 cups) would only treat 1920 gallons.
I want my decimal place back!

It says to use 2.6 parts ST per part Chlorine. So if my water has 1.5 ppm
of Chlorine and Chlorine weighs twice as much as water (guess). Then ten
gallons of water (UK) has .0048 ounces of Chlorine. So I would need .01248
ounces of ST. So my 5 lb bucket should treat 64,000 gallons.

This is closer to your number, but not quite. My guestimate of Chlorine's
weight could be off. Any math whizzes out there?





--
RichToyBox
http://www.geocities.com/richtoybox/pondintro.html

"Bill Stock" wrote in message
...
I just bought a 5 lb pail of Sodium Thiosulphate for the pond/aquariums.
The instructions I have read here in the past suggest that this should be
enough to dechlorinate lake Superior. But reading the bucket, it states
that I need anywhere between 1/4 tsp and 1 tsp of raw ST per 5 gallons of
pond water. This means that a 250 gallon water change would take up to 50
tsps. Given that the bucket only contains about 5 cups, that's 10 water
changes.

The stuff in the bucket looks like some sort of crystal, not a powder.
Has this stuff been bound with some other chemical to reduce it's
strength? At this rate it's no cheaper than the generic slime coat.
Bummer.