DIY Alk test discussion thread

[Randy Holmes-Farley]

:thumb:

Good luck.

 

[StikHedRon]

Randy, is there away to get more precise results without having to use greater than a liter of water? Say 500 ml of tank water but with a more accurate reading than .5 dkh with ever ml of acid added?

 

[Randy Holmes-Farley]

You can be as precise as you are able to measure the titrant liquid volume. So the device you use for liquid volume measurement determines that.

You can also use more dilute acid (0.01 N HCl), but that has its limitations as the endpoint won't be as clear since the liquid is diluting the sample as you add it.

 

[cope413]

I quit chemistry in school because I stupidly took quantitative analysis during summer.

15 years later I find myself shopping for cheap titration tools...

Irony

 

[JimWelsh]

I find a 50 mL burette to be a very nice "sweet spot" in terms of precision vs. volume for titrations. I use a weaker acid, 0.022M, and 10 ml of tank water. With this setup, it takes appx. 15 ml of acid per test, so I can fill the burette and it's good for 3 titrations. That way, I can do 3 tests in a row, and be more certain about my results.

 

[Randy Holmes-Farley]

A burette would certainly be the easiest way to do it. I've usually just used a graduated hand pipette.

 

[DFW]

Just let us know what you find.

Hi Randy!

I got the 1.0 N NaOH from eBay, and mixed 5ml of it with 995ml of fresh rodi water. I tested it with my API Alkalinity kit, and came up with about 12.3 dKH. How do I use this to make a comparison with the actual dKH of 14? 14/12.3 = 1.138, so does that mean that this kit reads approximately 13.8% too low?

Thanks again!

 

[Randy Holmes-Farley]

Hi Randy!

I got the 1.0 N NaOH from eBay, and mixed 5ml of it with 995ml of fresh rodi water. I tested it with my API Alkalinity kit, and came up with about 12.3 dKH. How do I use this to make a comparison with the actual dKH of 14? 14/12.3 = 1.138, so does that mean that this kit reads approximately 13.8% too low?

Thanks again!

Assuming your volume measurements were accurate, that's how I would interpret it.

 

[DFW]

Assuming your volume measurements were accurate, that's how I would interpret it.

Well, it's not nearly a perfect world, is it? :xd:But I did find out that a liter bottle of gatorade would have to be filled to the very top of the bottle to really be a liter. As it is, the bottle is a liter, but the contents are not.

Please let me rephrase that! It's not a perfect world outside of your lab, at least not on this end anyway!:wink:

 

[Randy Holmes-Farley]

Did you use a scale for measurement?

 

[DFW]

Did you use a scale for measurement?

I used a liquid measuring cup that measured 1000ml, and then removed 5ml before adding 5ml of the NaOH. Was I supposed to use a scale?

 

[Randy Holmes-Farley]

I used a liquid measuring cup that measured 1000ml, and then removed 5ml before adding 5ml of the NaOH. Was I supposed to use a scale?

Not "supposed to", but the measuring cup could easily be off by 5% either way. Do you have a scale?

 

[DFW]

Not "supposed to", but the measuring cup could easily be off by 5% either way. Do you have a scale?

Yes! I have a scale. I do not believe that it will be considered accurate either though, since it is a food scale, and I don't have anything of a known weight to calibrate it with either. How do I make use of it?

 

[DFW]

Not "supposed to", but the measuring cup could easily be off by 5% either way. Do you have a scale?

How do I make use of my scale for making this solution? Thanks!

 

[Shep]

So whats a good pH meter you suggest?

 

[Randy Holmes-Farley]

How do I make use of my scale for making this solution? Thanks!

How precisely can you read it?

Can you distinguish 500 grams from 510 grams?

 

[Randy Holmes-Farley]

So whats a good pH meter you suggest?

There are many good brands.

Most important is two point calibration.

 

[DFW]

How precisely can you read it?

Can you distinguish 500 grams from 510 grams?

Yes, it is marked in 20 gram increments, and I can read between the lines.

 

[Randy Holmes-Farley]

Yes, it is marked in 20 gram increments, and I can read between the lines.

That's fairly crude, but I'd try it too and see what you get. Use it to weigh the 1 L = 998 grams (because the density is not exactly 1.00000). If you cannot weigh that much, scale down.

 

[DFW]

That's fairly crude, but I'd try it too and see what you get. Use it to weigh the 1 L = 998 grams (because the density is not exactly 1.00000). If you cannot weigh that much, scale down.

Thank you so much! Have ordered calibration weights for my scale, too. Will weigh 1000 grams, then remove 7ml before adding 5ml of the 1.0N NaOH to get the 14 dKH solution. (I found out that 1ml of water weighs a gram. I did not remember that!)