# Cleaning Testing Tubes



## cheseboy (Aug 5, 2005)

Put some tap water and a heaping spoon of PH down in a glass tube. Shake it up and you have just cleaned your glass testing tube.


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## emantable (Jul 25, 2006)

What do you mean by pH? pH is a logorithmic scale used to measure acidity levels. It's like saying "put MPH (miles per hour) in your gas tank to make your car engine cleaner." I'm sure your suggestion is great for cleaning test tubes but I'm a little confused on what you mean by pH.
Rinsing test tubes with just tap water is fine. Deionized water works best if you have access to it. Be careful if you're using acid to clean the test tubes (if that's what you mean by pH). Although acids work miracles in getting rid of precipitates in test tubes, its use can be dangerous for the fish and you, and can also dissolve test tubes if you're using the plastic ones and with the right type of acids.


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## Reefneck (Oct 15, 2005)

He said use "PH Down"


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## Guest (Jul 26, 2006)

Why do you use pH down? Just wondering the reason for this.....

I just rinse mine...I thought that was good enough.


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## harif87 (Jun 5, 2006)

pH down is just a weak acid- usually somehting like phosphoric acid (H3PO4). Although its a "weak" acid it still does a good job of reacting with the things it comes into contact with. In theory you could use a stronger base as well since that too would react.... but the thing im skeptical about is the byproducts of the reactions between H3PO4 and whatever is in the test tube


now that you think of it.....could pH down cause algae blooms since its got the phosphates? I know that if H3PO4 is dilluted it benefits plants.... hmmmm


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## Guest (Jul 26, 2006)

Ok I see....I just wondered why they used that.


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## emantable (Jul 25, 2006)

I had understood that he had said pour Ph down, as in into, the test tube. I didn't realize he meant pH down. pH down will probably not contain phosphoric acid (H3PO4) especially if they're meant to be used in the marine aquarium. They use chemicals like combinations of sodium bisulfate (NaHSO4) and sodium sulfate (Na2SO4) (I think they use the anhydrous form), or bicarbonate (HCO3-) and carbonic acid (H2CO3) which are much safer for fish without promoting unwanted algae growth. Sodium bisulfate and sodium sulfate solutions are more common for treating ponds. Since the marine aquarium contains many sensitive fish and invertebrates, the bicarbonate and carbonic acid is used because it is naturally occurring as a buffer in blood of animals like fish and mammals that have a closed circculatory system and in the hemolymph of animals that have an open circulatory system as in shrimp and other arthropods.

The reason sodium sulfate and sodium bisulfate are used in pH down is that they produce a neutral solution (pH 7) because Na2SO4 is derived from a strong acid (sulfuric acid) and a strong base (sodium hydroxide). They form very stable salts so there are no worries about these dissociating in water to form the very toxic sulfuric acid or sodium hydroxide solutions.

It is not my intention to beat anyone senseless. On the contrary, I wish to provide everyone here with as much information as possible to make sure everyone is informed and because I respect the intelligence of everyone here.

I don't believe I beat anyone senseless here. If anyone is a little confused I invite you to read up on the subject because informed people are never a bad thing.


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## harif87 (Jun 5, 2006)

Emantable, i as well as everyone esle (im sure) respects your diplomatic approach. Glad to have someone like you on the board 

About the phosphoric acid, im almost positive that the brand i use (dont remember the name off hand) uses H3PO4 as the reagent to lower the pH. What you say about the carbonic acid is probably the norm for most other brand's pH lowering reagents since it does benefit the aquarium in a few ways.

Also if i remember correctly strong acids and bases completeley dissociate in water which is why they have a greater Ka value. I dont see how the NaHSO4 wouldnt turn into sulfuric acid if added to the water since in the ion form it would be Na+ and HSO4-. The truth is it could go either way, HSO4 can act as either an acid or a base, but there is a possibility that it would accept a proton to become the strong acid H2SO4. 

I dont think companies would put a strong acid in their products since it would be harmful to the fish, which is why (to me) it makes sense to have somehting like H3PO4 or H2CO3 since those are weaker acids.

Also i dont know what you meant when you said that they use Na2SO4 or NaHSO4 in an anhydrous form. I got a little lost since one is an acid and one is a base and the reagents sold as pH up and pH down arent anhydrous. Maybe they sell pH up and down in a powder?


Anyways i must say that its great to meet another chemistry buff who knows what hes talking about  like i said before, welcome to the boards


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## emantable (Jul 25, 2006)

You are absolutely correct!

NaHSO4 completely dissociates in water into the Na+ and HSO4-. That is why they use it together with Na2SO4. 1 mole of Na2SO4 combines with 1 mole of the resulting H2SO4 to form 2 moles of NaHSO4. A pH change will cause a change in the equilibrium that will either favor the forward or backward reactions to stabilize the pH. The reaction is quite safe for its use in ponds or swimming pools.

Na2SO4(aq) + H2SO4(aq) → 2 NaHSO4(aq)

Sorry for saying they don't dissociate because as you correctly pointed out they do. What I meant and didn't cleary explain is that at equilibrium, sodium sulfate and sodium bisulfate act as a buffer to prevent the accumulation of dangerous acids.

While I haven't used or bought these reagents myself (I don't have a large pond or pool:-( ), I have heard that Na2SO4 is used in it's powdered form for large applications like in ponds at public parks. Both the anhydrous and the decahydrate forms are solid and look like white crystals (much like the appearance of salt). The most likely reason for a powder being favored for large applications is that it is cheaper to ship and easier to store than it would be if it were in solution. 

The reason I said I believe they use the anhydrous form is that the decahydrate form of Sodium sulfate (Na2SO4•10H2O) was used as a laxative and I wasn't sure if it would cause the same effect on other animals as it does in humans.

Also I take back me saying it being more suitable for the marine aquarium since corals are very sensitive and I'm not sure what effect these would have on them. The chemicals I use to buffer and regulate the pH contain carbonic acid and bicarbonate. I did some research on the internet and saw that some pH down solutions do indeed use H3PO4. So I wonder if they have some way to prevent phosphate from being released into the water to prevent algae growth. I'll need to do more research on that. Any help?

Thanks for the welcome! I must also say that it's great to see other's interested in chem and/or bio.


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## harif87 (Jun 5, 2006)

emantable said:


> You are absolutely correct!
> 
> NaHSO4 completely dissociates in water into the Na+ and HSO4-. That is why they use it together with Na2SO4. 1 mole of Na2SO4 combines with 1 mole of the resulting H2SO4 to form 2 moles of NaHSO4. A pH change will cause a change in the equilibrium that will either favor the forward or backward reactions to stabilize the pH. The reaction is quite safe for its use in ponds or swimming pools.
> 
> ...


I love you


where did you study your chemistry?


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