Salifert KH Test Question

[jeffblly]

I am using the Salifert KH/Alk Test and am getting different results on the level of kh regent on step 3. The tests says to stop at the lower end of the 1.00 ml mark but when I do that, the level of the kh regent is sometimes at the 8.0 mark and the 8.5 mark. I know there should be some air below 1.00 but shouldnt the KH regent be at the same level mark each time I test and if so where is the level supposed to be at?

 

[CoryC]

I noticed this too. It's because there is residual fluid left in the application tip. I interpret the test to mean I shouldn't have any fluid in the tip so I shake it out before sucking up the reagent which leaves it around the 8ml mark and I have gotten the best results with. This has happened w all the reagent kits.

 

[Palting]

Make sure to completely empty the syringe before you stick it into the reagent bottle to draw up the liquid, then make sure the tip is always submerged as you draw it up. The air space between the bottom of the rubber plunger and the reagent level in the syringe should then be constant. Regardless, it doesn't really make a difference, since your reading is based on how far the plunger has travelled. Example, the plunger bottom went from 1.0 to 0.54, then you have a reading of 7.0dKH, if memory serves me right. It doesn't matter where the actual level of the reagent is in the syringe.

 

[jeffblly]

I noticed this too. It's because there is residual fluid left in the application tip. I interpret the test to mean I shouldn't have any fluid in the tip so I shake it out before sucking up the reagent which leaves it around the 8ml mark and I have gotten the best results with. This has happened w all the reagent kits.

That makes sense. I will check from now on. Thanks.

Make sure to completely empty the syringe before you stick it into the reagent bottle to draw up the liquid, then make sure the tip is always submerged as you draw it up. The air space between the bottom of the rubber plunger and the reagent level in the syringe should then be constant. Regardless, it doesn't really make a difference, since your reading is based on how far the plunger has travelled. Example, the plunger bottom went from 1.0 to 0.54, then you have a reading of 7.0dKH, if memory serves me right. It doesn't matter where the actual level of the reagent is in the syringe.

But it seems it would matter since I am reading the the exact amount off the syringe and if I have more fluid in the syringe then I should, it will turn pink faster and my readings will be off.

 

[Palting]

But it seems it would matter since I am reading the the exact amount off the syringe and if I have more fluid in the syringe then I should, it will turn pink faster and my readings will be off.

It doesn't matter how much fluid you have left in the syringe, what matters is how much fluid you gave before it turned pink. In the example I gave, where the plunger went from 1.0 to 0.54, you dosed exactly 0.46 of the kh reagent for the water to turn pink. Whether the reagent level in the syringe started at .85 or .80, you still only dosed a total of 0.46 of the reagent for the water to turn pink. Anyhow, as has been stated, you can avoid any confusion by making sure the syringe is completely empty before you refill it, and keep the tip totally submerged the whole time so that the reagent level in the syringe is constant at 0.8 when the plunger gets to 1.0.