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View Full Version : KMnO4- please check my chemistry


sl-atl
10/12/2009, 05:37 PM
I'm pretty sure that I have monti eating nudibranchs, again, so I've resolved to kill them before they kill my corals and gotten some lab grade KMnO4, but, am not 100% sure how to proceed from there...

Based on on Eric Borneman's article, I would want a dip with 50mg/l. Now, I have a lab grade powder that I assume is 100% pure. I guess I'll make 1l of the solution, so...

C1V1=C2V2
where C2=50mg/L
and V2=1L

C1V1=50mg

Does that mean that I would simply add 50mg of the pure substance to a 1l of water? That seems a little too easy, especially since I less than aced Chem 101. - but give me a break I was an EE. ;)

Now if I got that far correctly, since I don't have a balance I would need to convert from mass to volume. Assuming 2.703 g/mL for KMnO4:

0.050g /2.703g/ml = 0.0185ml

So... I would add 0.0185ml of the powder to a liter of seawater. (?)

I'd really appreciate somebody checking my work before I start dipping a couple hundred dollars worth of corals!

Thanks,
Stuart

bertoni
10/12/2009, 05:58 PM
If you want 50 mg/L, then just add 50 mg to a liter of water. That'd be about 50 ppm potassium permanganate. Do you have the exact wording from the article in question?

sl-atl
10/12/2009, 06:26 PM
Thanks- the suggested dosage is 50mg/l (http://reefkeeping.com/issues/2007-09/eb/index.php).

Maybe looking at it another way in terms of adding a dilute solution to the dipping container... 1/4 teaspoon or 1.232 ml in 1 liter would yield a concentration of (1.232 ml)*(2.703 g/ml)=3.331 g/l or 3331 mg/l <-- The concentration of the solution I'll add to the dip water.

So, if I use the C1V1=C2V2 equation again, and assume that I'll use a liter of water for the dip...

3331mg/l * V1 = 50mg/l * 1l
V1 = 50/3331 = 15 ml of the concentrated solution?

How does that look? :)

bertoni
10/12/2009, 06:43 PM
I'm a little worried that the density number might be off, but the lethal dose for corals seems to be fairly high. The math all seems correct to me.

sl-atl
10/12/2009, 06:54 PM
Thanks! I got the number from a MSDS. To double-check the density, I put the CAS number from the bottle into the MB database and it gives a value of 2.7 (http://www.jtbaker.com/msds/englishhtml/P6005.htm)

Thanks again- I really appreciate it. I'm going to try a 60 minute dip instead of the 90 minute that Borneman used, and will see how it goes. :)