Problem with Salifert Alkalinity (Kh/Alk) test??

No. You're mistaken I'm afraid. As you push the plunger down you are displacing (dispensing) titrant. You will displace the exact same amount of titrant whether there is .25ml of air, .15ml of air or .3ml of air. As long as there is still itrant left in the syringe at the end of the process. The same amount is being displaced regardless. It's dispening from the fluid end of the syringe. Not the 'air' end. Try it yourself. Fill the syringe with two different sized 'air pockets'. Now slowly dispense and count the drops for 0.1ml. It will be the same.
 
Make sure the tip is applied firmly to the syringe or just leave it on. Applying it with different pressure can lead to a larger or smaller air gap. If you leave it on it should yield same results each time.
 
<a href=showthread.php?s=&postid=15384532#post15384532 target=_blank>Originally posted</a> by jtma508
No. You're mistaken I'm afraid. As you push the plunger down you are displacing (dispensing) titrant. You will displace the exact same amount of titrant whether there is .25ml of air, .15ml of air or .3ml of air. As long as there is still itrant left in the syringe at the end of the process. The same amount is being displaced regardless. It's dispening from the fluid end of the syringe. Not the 'air' end. Try it yourself. Fill the syringe with two different sized 'air pockets'. Now slowly dispense and count the drops for 0.1ml. It will be the same.
Click to expand...

But the reading is taken from the black plunger, not the liquid level!
 
actually, i think you might be right jtma508... the results would only be skewed if you were dispensing all of the fluid, which like you said would never likely be the case anyhow. problem solved, foot is now in mouth.
 
Wow. Guys. Stop and think for a minute. You have a syringe with titrant in it and the plunger set at the 1.0ml mark with some arbitrary pocket of air in it. You now push the plunger so it is on the 0.6 mark. You have just dispensed 0.4ml of titrant. The air pocket, hwoever big or small it is is still in the syringe happily smiling at you. The only thing that has left the syringe is 0.4ml of titrant. Which would convert the color for an alkalinity of 6.4dKh.

The air pocket has no affect whatsoever as long as there is still titrant in the syringe when you finish.
 
NP. Some of us have taken alot more chemistry than others. Did you check your test kit against the 'standard' they supply in the kit?
 
<a href=showthread.php?s=&postid=15384645#post15384645 target=_blank>Originally posted</a> by jtma508
NP. Some of us have taken alot more chemistry than others. Did you check your test kit against the 'standard' they supply in the kit?
Click to expand...


Yes and it was way off. It was supposed to be an alk of 7.6 and I got 12.4. I still think there is something tricky with these kits.
 
There were some kits that were reading 2-3 dKH on the high side some time back and there have been some scattered reports of problems with kits even after the problem was "fixed".
 
The air pocket has no affect whatsoever as long as there is still titrant in the syringe when you finish. [/B]
Click to expand...

And you are reading either the stopper or the liquid level at the start AND the finish, which is where the confusion in this thread comes from.

Basically, assuming the seal on the stopper holds, you can either fill the syringe so that the stopper is at 1.0, then titrate, then read the stopper,

or

Fill the syringe so the liquid level is at 1.0, titrate, and read the liquid level.


Either should get you the same result, since the volume of air between the two should be constant.
 
I know they had problems in the past with the Alk kits but I've not heard any squawks lately. It's critical when you dispense the 4ml for the test that it's done accurately. Submerge the tip of the sample syringe (the 5ml one) and run the plunger two or three times to push all the air out of it. Push the plunger until it is exactly on the 4ml mark and dispense that into the test tube.

If you test the standard (do it a couple times) and get a reading other than what is on it (in your case 7.6dKh) you calculate an adjustment factor: standard value/your reading or in the case you cited above 7.6/12.4 or 0.613. You multiply all your test values by this factor to get an accurate result. So if you tested your tank and got a reading of 11.8, you'd multiply it by the factor and get 11.8 * 0.613 = 7.1 (the real Alk in your system)

In my experience though, you shouldn't be getting readings so far off. It makes me suspicious that something isn't right.
 
I've always used Salifert for Calcium and Magnesium in my tanks. Never had any problems with them.

I've never had a problem with their Alkalinity kits either. Had I come across a problem I'd switch that kit over to Elos.
 
I use Salifert for everything right now. But I recently got an Elos nitrate kit and prefer it to the Salifert. I might try Elos for CA and Mg next but I've had no complaints with the Salifert.
 
salifert works great for me. It clearly tells you in the instructions that you will have an airpocket between the liquid and the plunger and that it's normal.
 
I use nothing but Salifert tests and the KH is way easy. Can't figure out what the problem is unless you're trying to adjust your KH by tenths. Good luck!
 
The difference is the volume of the tip itself. Thats why there is air in there. Which is supposed to be there if you read the directions all the way through. Even if you used all of it and had to dose more and refilled it there wouldn't be a problem, becasue I have done it.
 
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