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

David - Miami

David - Miami

Aquanot!
I purchased one last week and I can not get an accurate reading. I have tried to find a website to ask them directly, but have been unsuccessful.

If anyone who has this kit can help I would greatly appreciate it. My problem is when I fill the small syringe with the Kh solution. It says fill until the rubber stopper is at 1ml. I do that, but that results in the liquid level being somewhere between 0.75 and 0.86 (not consistent at all). It is not that it is not submerged, I have been careful. I need to know where the correct liquid level should be to begin the test, not the rubber stopper. Does anyone know the answer or know where I can get the answer please?
 
well those readings suggest your dkh reading is 2.2-4.2, very very low, when you use the regent the lower end of the black bit needs to be at 1.0 ml, drop slowly until the color changes from blue/green to a pink/red color, the test is complete as soon as the color changes, its easy to press the syringe too much and get different readings, hence the need to do it very slowly and stop as soon as the color changes
 
<a href=showthread.php?s=&postid=15383961#post15383961 target=_blank>Originally posted</a> by Michael
well those readings suggest your dkh reading is 2.2-4.2, very very low, when you use the regent the lower end of the black bit needs to be at 1.0 ml, drop slowly until the color changes from blue/green to a pink/red color, the test is complete as soon as the color changes, its easy to press the syringe too much and get different readings, hence the need to do it very slowly and stop as soon as the color changes
Click to expand...

oh edit haha, the liquid level will be below the 1.0 ml mark as there is an air gap, not sure of the exact measurement tbh, but its not vital as long as the stopper is right
 
That is not my readings. That is simply the amount of the reagent that the small syringe draws in when the black bit is at 1.0ml. Therefore the test is extremely inaccurate. That is why I am asking about the liquid level in the syringe.
 
As Michael said, they allow for the air that is already in the tapered tip in their calculations, so there will be an air bubble right below the rubber stopper in the syringe. This is intentional and ok.
 
The difference in levels could be when you do an immediate repeat test? A test done on a dry syringe will have air in the needle cap, a secondary test right after will still have fluid left in the cap, maybe increasing the fluid level and decreasing the amount of air? will have to try this at home tonight...
 
<a href=showthread.php?s=&postid=15383978#post15383978 target=_blank>Originally posted</a> by David - Miami
That is not my readings. That is simply the amount of the reagent that the small syringe draws in when the black bit is at 1.0ml. Therefore the test is extremely inaccurate. That is why I am asking about the liquid level in the syringe.
Click to expand...

oh-ok david i see, my mistake, well theres clearly a problem, id suggest a new syringe then and best of luck :)
 
This would all be moot if they would clarify the appropriate liquid level rather than the stopper level. I understand how the difference could happen, but I do not know where the correct one is. This makes a huge difference in the test and that is what I am trying to resolve.
 
Just take the beginning reading and subtract the final reading. If the liquid reading is .90 ml and the final reading is .40 then you used .50 ml of reagent.

And yes it can be confusing.
 
ok david ive just filled my syringe twice and both times the water level was 0.8, i hope this is useful :)
 
What he's saying is that the liquid level isn't consistent, which is going to cause a difference in his end result. I abandoned Salifert alkalinity kits a while ago and will not touch another Salifert product as I replace my kits. Too many issues, and when you have an issue Salifert has no customer support. Their e-mail doesn't work, there's no phone # and Habib seems to have dropped off the face of the earth.

Someone correct me if I'm wrong, but I believe Salifert went to a single reagent acid titration similar to what most other companies use. The kit you got is the old style and there were certainly some issues with it. I personally had two bad kits, one of them after the problem was supposed to have been fixed.

I'd just save yourself the headache and get a cheap API kit. Easy to use, pretty reliable, and essentially the samke reagent as other far more expensive test kits. The only thing I don't like about the API kits it the vial, so I juse my salifert "vial" and a 5ml syringe.
 
It won't matter as long as you're using their table. The test is done on a 'to deliver' basis. As long as you're not using the entire syringe worth of titrant (and you shouldn't be by any means) the test will come out correctly whether the air pocket is the same or not. The table tells you how much titrant you've used based upon the displacement of the plunger from 1.0ml. Unless you find yourself in the syringe's 0.1 neighborhood during the test it's a non-issue. And if you're testing that high you are outside the test kit's reliable range anyway.
 
No it doesn't. You always start with the base of the plunger on 1.0. You start dispensing from that point and the plunger slowly works its way down the barrel toward the lower numbers until the color change. You read the bottom of the plunger, look it up on the table (which converts from plunger position to titrant dispensed) and there is your answer. The size of the air pocket is irrelevant.
 
If the plunger starts at 1.0ml and the liquid starts at .75ml then the solution turns pink at say .2ml, that will give you a different alkalinity level then when the liquid starts at .85ml. If the plunger is at 1.0ml and the liquid is at .85 ml, the solution would turn pink at .3ml. Therefore it is not the same result and inaccurate.
 
edit: let me rephrase; variable air volume = variable fluid volume = VARIABLE (read inaccurate) results!
 
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