Testing kh with Salifert

[Higher Thinking]

Hey everyone,

So I posted this before, but I wanted to see if there were more opinions. The Salifert test kit comes with a calibration fluid that is 6.7 dkh. You are suppose to add the titration fluid until it turns "from blue/green to an orange/red or pink color, whichever color is observed first)."

 

This is my problem. When I use the calibration fluid and add enough fluid for it to be 6.7, it looks very purple.

 

When testing my tank, I always continue adding until I get a legitimate pink color. The difference between purple and pink is not huge, but it is about 1.0 dkh. Here are some pictures. I added the benadryl so people could compare colors with some kind of constant. The purple is the calibration fluid and the pink is where I test to. Who uses these tests and what color do you shoot for? If I had a different test I'd compare them, but I only have Salifert.

 

 

[rworegon]

I'm sorry I can't help with this but I use the Hannah alk checker. Takes all the guesswork out if the colors.

[reefnjunkie]

I was just re-posting this

 

The best alk testing is doing your own acid titration down to a ph of 4.2, super accurate and super cheap because you have to buy the acid by the gallon so you will have enough for years of use . Initial investment is a ph meter and the gallon of acid...good for years of testing!

 

 

here is a clip from rc chemistry guys

 

The best alk testing is doing your own acid titration down to a ph of 4.2, super accurate and super cheap because you have to buy the acid by the gallon so you will have enough for years of use . Initial investment is a ph meter and the gallon of acid...good for years of testing!

 

 

here is a clip from rc chemistry guys

You can buy 0.1 N Sulfuric acid standard used as the titrant from:

 

 

http://www.grainger.com/Grainger/items/4YNA6?cm_mmc=Google%20Base-_-Test%20Instruments-_-Laboratory%20Supplies-_-4YNA6[/url] also sells 0.1 N sulfuric acid standards.

 

 

It may be best to calibrate your pH meter using a 4 & 7 standard before you start the test.

 

 

 

 

Easy part; Testing

 

 

Now take a sample of your aquarium water, you can use any volume but I like to use 100ml because my pH meter sits nicely in the cup without me holding it at this level. Stick in your pH meter to your sample. You should get the same reading you do when you stick it directly in your tank. If not start over with a clean sample container. Now draw up some 0.1 N HCl solution in to your 5ml syringe. And start dropping into your sample 0.5 mls at a time and watch your pH meter. You are adding a strong acid so your pH should fall rapidly. Once your pH hits 5 start to slow down and add a drop at a time until your pH hits 4.2 . The reason we are shooting for 4.2 is because this is the point where all available carbonates have been converted to carbonic acid. You would think this would be pH 7 but it's not as carbonic acid is a weak acid and you have to really saturate it etc. Anyway, once you have reached pH 4.2 you are done and now can calculate your total alkalinity.

 

 

 

 

Alk mg of CaC03 /L = A x N x 50,000 / mL of sample

 

 

Where A = ml of acid added

 

 

N = normality of your HCL

 

 

So if you added 4ml of 0.1 HCL before you hit a pH of 4.2

 

 

4*0.1*50,000 / 100 = 200 ppm CaC03 equivalents or your total alkalinity is 4 meg/L (mg/L / 50 = meg/L).

 

 

 

 

The above information was taken and corrected from this thread:

 

 

http://www.reefcentral.com/forums/sh...ion+alkalinity

 

 

Randy provides further details in this article:

 

 

What is Alkalinity

http://www.advancedaquarist.com/2002/2/chemistry

 

 

 

 

 

 

__________________

Cliff Babcock

 

 

 

 

I know this seems a little "geeky" at first and difficult but it really is not... It takes about a minute to perform and if you do all the calculations and make a chart ( xml used = 10dkh and so on) it makes it very easy with NO math. If anyone would like to see how this is done you are welcome to come to my place and I can show you.

[Bicyclebill]

I used Lamotte for 10 years or so. Switched to Hanna checker and it's about 2.5 dkh lower, and matches cheapo API spot on. Now I just pull out the API every once in a while.

[Higher Thinking]

I was just re-posting this

Hey thanks for that post. I actually have a Reef Fanatic pH controller, but no probe. I don't even know if anyone sells the RF probes anymore.

I used Lamotte for 10 years or so. Switched to Hanna checker and it's about 2.5 dkh lower' date=' and matches cheapo API spot on. Now I just pull out the API every once in a while.[/quote']

 

Thanks for the insight.