Salifert Alk Test Reagent

[SDguy]

I have the older style salifert alkalinity test kit, the one with the small indicator bottle (blue/green) and the titration reagent.

Well, as anyone with a decently high alk level in their tank can confirm, I used up my titration reagent MUCH faster than the indicator. So, I tried making a new reagent at work, since I was pretty sure it is just a weak acid.

It worked!!

First, I tried calculating mathematically what molarity HCl it should be:

200ppm alk:

200mols CO3/1,000,000 mols water =

2molsCO3/10,000 mols water or 2molsCO3/180,000 g (mL)

For my 2mL water samople, that gives 0.000022mols CO3

That would require 2 fold molar ratio of H, or 0.000044 mols H

in 0.4mL of volume (the amount I use from the original kit) =

0.000044mols/0.0004L = x/1 or 0.11M HCl.

which we conveniently already have here at work used for titration

[SDguy]

Well, that didn't work, so then I just diluted it out. Finally, I got this:

First, I'm using a standard I made with Na2CO3 anhydrous. 0.312g into 1L. According to the reef chem calculator, that comes to about 16.6dKH. I use it diluted 1:1 with DI H2O, so it should be 8.3dKH.

My current Salifert kit, using all its reagents, and a 2mL sample, gives:
(1.0 - 0.73) = 0.27 x 16 x 2 = 8.64dKH close enough for me.

OK, so 0.1N HCl was too strong

Using 0.02N HCl I get:
(1.0 - 0.7) = 0.3 x 16 x 2 = 9.6dKH

to correct for the error, I do:

0.3 x 13.83 x 2 = 8.3 dKH

OK, just to confirm, I tested my standard full strength and got

(1.0-0.41) = 0.59 x 13.83 x 2 = 16.32dKH (close enough to the 16.6dKH it should be).

[SDguy]

Even Randy, chem guru on RC gave me the thumbs up, so I'm good to go.

Tested my tank last night. Works perfectly!

So anyone with leftover indicator reagent from an older salifert alk test kit? I can make you a usable titration reagent.

BTW, here is the whole thread on RC:
http://www.reefcentral.com/forums/showthread.php?s=&threadid=1338266

[DaveMorris]

And you actually expect me to understand all of that? You are a mad scientist.

[SDguy]

http://i124.photobucket.com/albums/p5/SDreefguy/smilies/MadScientistPicture.gif

[coral diver]

I know all it sounded is BLAH! BLAH! BLAH! BLAH!
Sorry Peter but if its OK just plain ENGLISH please Mr. Genius

[SDguy]

Sorry Peter but if its OK just plain ENGLISH please Mr. Genius


Tested my tank last night. Works perfectly!

So anyone with leftover indicator reagent from an older salifert alk test kit? I can make you a usable titration reagent.

.....................There you go :D

[pollywog]

My head hurts.

[MichaelRyanSD]

LOL..its funny because at the point at which you said
"200mols CO3/1,000,000 mols water "

I was like......I'm Done...this is to much for me

[SDguy]

Oh, c'mon guys...no math for the masses Friday morning?? :D

Besides, my calculations didn't work anyways, so clearly I don't get it either :o

[swissfish]

Well, that didn't work, so then I just diluted it out. Finally, I got this:

First, I'm using a standard I made with Na2CO3 anhydrous. 0.312g into 1L. According to the reef chem calculator, that comes to about 16.6dKH. I use it diluted 1:1 with DI H2O, so it should be 8.3dKH.

My current Salifert kit, using all its reagents, and a 2mL sample, gives:
(1.0 - 0.73) = 0.27 x 16 x 2 = 8.64dKH close enough for me.

OK, so 0.1N HCl was too strong

Using 0.02N HCl I get:
(1.0 - 0.7) = 0.3 x 16 x 2 = 9.6dKH

to correct for the error, I do:

0.3 x 13.83 x 2 = 8.3 dKH

OK, just to confirm, I tested my standard full strength and got

(1.0-0.41) = 0.59 x 13.83 x 2 = 16.32dKH (close enough to the 16.6dKH it should be).


This is exactly what I told you to do years ago :D

Here is what you should have posted:

OK guys i made a replacement liquid for the salifert dkh test kit, hit me up if you want some.

This way we would not feel that stupid and dumbfounded :D

[SDguy]

Well that wouldn't really be much of a DIY thread, now would it? :p

[cfamaya]

Mr Peter do you have a replacement liquid for the salifert dkh test kit? if so how much, I'm going thru mine quick.

Thank you

Carlos

[Fine Fins]

of course your mole ratio was off. yes that can happen to anyone mixing acid. I drop it on my colths all the time wife hates it.

[SDguy]

Mr Peter do you have a replacement liquid for the salifert dkh test kit? if so how much, I'm going thru mine quick.

Thank you

Carlos

Sure. You need to have the indicator reagent though...I can't make that.

[SDguy]

of course your mole ratio was off. yes that can happen to anyone mixing acid. I drop it on my colths all the time wife hates it.

I don't think it was so much my calculations, as it was not including the complexities of what happens as acid is added to buffered water. Randy explains it quite well here:
http://www.advancedaquarist.com/2002/2/chemistry

Check out the section titled Step by Step Acidification

[cfamaya]

Excuse my dumb question but what is indicator reagent?
did the older kit have two agents? all I have in mine is the reddish agent & a clear test solution.

Thanks

Carlos

[SDguy]

Yes, the older kits came with an indicator reagent, and a tirtation reagent (but no "test solution" aka standard).