[fry lover]

Hi All

I'd be so grateful on some feedback, comments on this

I am a fish-keeper doing some of my own research into a chemical filtration product i am using that when exhuasted gets "recharged" in a 1:1 bleach solution

I just wanted to confirm a few things with you guy's that i think i am learning about chlorine based bleach..


1. General household bleach will contain 5.25% Sodium Hypochlorite as the active ingredient


2. Is Sodium Hypochlorite basically the bleach then? Can i assume normal household chlorine based bleach contains 5.25% "free chlorine"?


3. I am under the impression that normal household bleach that contains 5.25% Sodium Hypochlorite will provide the following levels of chlorine

1:100 bleach/water mix = 525ppm chlorine

1:10 bleach/water mix = 5000ppm chlorine

Is this correct, or very close?


4. I understand chlorine in water can be quite unstable. Am i right in assumming the following can "de-activate" chlorine (is that the right word, or should it be drive-off chlorine?)

- aeration, agitating the water to increase o2 content
- refridgeration
- exposure to light

Is any method more efficient at driving-off / reducing the chlorine content of water than the other methods?

The comany's instructions is to basically use a product that many of us fish keepers use to neturalise any left over chlorine in our tap water (we use various products that contain sodium thiosulfate that act as de-chlorinator's)

I am following the company's instructions and soaking the media in a 1:1 bleach solution for 24 hrs then rinsing a few times in tap water and then soaking in the de-chlorinator solution for 8-hrs but this whole thing has got me more interested in bleach and how it works etc

If anyone has time to kill and wants to know what the heck i am talking about, this is the product

http://www.seachem.com/products/product_pages/Purigen.html

[Borek]

5.25% - more or less. I would say "something around 5%" as producers prefer to use cheaper substances (like water).

Now, conversion between sodium hypochlorite and "free chlorine" is not that simple as you think. Not that it is much complicated. 74.4 g of hypochlorite contains 35.5 g of chlorine - around half of the mass. I would go for 5.25/2 =  2.6%, or 2.5% to make calculations easier.

Your ppm levels are off by the factor of 2 - you have calculated them correctly, just your conversion between hypochlorite and chlorine was wrong.

Now, to get rid of chlorine you can either physically remove it from solution - things like aeration and agitation will speed up the process, or reduce it to chlorides making it chemically react with something (thiosulphate does just that). Also many organic substances that are always present in the tank react with chlorine as well, just slowly and not necesarilly yielding chlorides, rather chlorinated compounds, but chemistry here can be quite complicated. In general neither freezing nor light won't change chlorine level.

[fry lover]

Thank you Borek

Do you think placing tap water (standard concentrations of chlorine in tap water in my area is 0.3 to 0.5 mg/l) in the fridge for 12 hrs will not specifically yield any higher level of de-chlorination than leaving a solution of tap water at room temp?

I might have picked this up as a some kind of "myth" that sticking tap water in the fridge speeds up dechlorination at a quicker rate than room temp (and therefore my point being if this is true, then perhaps the chlorine content on say a 1:10 bleach/water solution would reduce faster in the fridge).

I was under the impression that daylight effects the stability of chlorine in water (but whether daylight/sunlight) speeds up the process of chlorine leaving the water is not clear to me?

I think you are saying sunlight would have no specific effect on the rate of chlorine leaving the water?

Thanks for your feedback

[Borek]

If anything (could be I am missing some fine points) I would expect cooling to slow down the process. First, eveything in general goes slower at lower temperatures, second, gases solubility goes up in low temp.

Presence of light may speed up reactions in which chlorine takes part, but I am not aware of any process in which light will speed up process of leaving water.

Two things that come to mind are boiling and acidification of the solution. I should put number of security related disclaimers here, as chlorine is toxic. Check pH of the solution after rinsing your filter with water - if it is above 7, adding minute amounts of hydrochloric acid should help. But details - ie final pH after acid addition - will depend on the circumstances and I am not sure if the gain is worth the effort.

[fry lover]

Borek

I have been searching the boards on here about Chlorine, i stumbled across a thread where you mentioned the effect Vinegar can have on eliminating (or vastly reducing) chlorine content.

With the pH of house-hold bleach being very high (11 to 13 ranges i am getting according to Google) the manufacturer's of this filter media for my fish tank recommened that after the de-chlorinator is used, the media is "buffered" in a solution so as to not adversely increase the pH of tank water once the media goes back in the tank (after it's been re-charged).

The company recommened their own buffering (of the pH) chemical to do this, but the company have also acknowledged a vinegar solution can be used (not sure on what strength and how long).

My question being, if there was any bleach residue left on the media by the time i got to the buffering of the pH stage, do you think a vinegar solution would help further eliminate any final traces of bleach?


Am i right in thinking that once you eliminate the chlorine from chlorine-based normal bleach, and rinsed off whatever was in the bleach solution, the substance in the 1:1 bleach solution is virtually harmless to aquatic life? I know thats going into a slightly different area now, just wondered if you or anyone had a view on it?

Thanks

[Borek]

My question being, if there was any bleach residue left on the media by the time i got to the buffering of the pH stage, do you think a vinegar solution would help further eliminate any final traces of bleach?

Definitely. Although it will not just "eat" the chlorine (like thiosulphate does), it will speed up hypochlorite decomposition to chlorine that will leave the solution.

Am i right in thinking that once you eliminate the chlorine from chlorine-based normal bleach, and rinsed off whatever was in the bleach solution, the substance in the 1:1 bleach solution is virtually harmless to aquatic life? I know thats going into a slightly different area now, just wondered if you or anyone had a view on it?

Honestly, I don't understand your question. But I will do my best.

First of all, bleach doesn't contain only hypochlorite. It may contain some additives, that I will not put into my aquarium. At least bleach that I have here contains some "other disinfectants".

Second: after rinsing concentrations of everything that was in the bleach is many times lower than at the beginning (thus no idea what do you mean by 1:1).

Third: if you have added anything (like vinegar, or hydrochloric acid) to lower pH, you will end with some salt - be it sodium chloride or sodium acetate. No idea about acetate effects, but sodium chloride means salty water. Rinsing will help get rid of most of the salt, so it is very likely that after rinsing your fish are safe.

[fry lover]

Yes my last question was a bit muddled, but thanks for clarifying the vineger issue