Alkalinity standard solution diy?

Heisenberg · Jan 27, 2015

Hello.

I have an issue, my 3 alkalinity tests (Red Sea, Salifert and api) ALL have different readings on the same aquarium.

Does anyone know how to make a standard solution so I can figure out which is most accurate? Thanks

JimWelsh · Jan 27, 2015

One approach: Take 15.90g of thoroughly dry sodium carbonate, and dissolve it into 1 liter of pure (RO/DI) water, using a volumetric flask. This gives a 300 meq/L solution. Then, do two 10x serial dilutions (or one 100x) using volumetric glassware to get it down to a 3.0 meq/L solution. At least, that's what I did.

Randy Holmes-Farley · Jan 27, 2015

We discuss that as well as a DIY alk test here:

https://www.reef2reef.com/forums/re...urself-alkalinity-test-discussion-thread.html

DFW · Jan 27, 2015

I made that solution with Randy's help at the thread he gives the link to above.

I ordered the 1.0 N NaOH solution off of eBay for around $25 delivered, and I ordered a set of calibration weights from eBay to calibrate my scale for nearly $7 delivered. I then weighed out 1000 grams of fresh ro/di water. Then I removed 7ml of that water with a 5ml syringe. Then I added 5ml of the 1.0 N NaOH solution, and stirred it in a bit. This is a comparison solution with a dKH very close to 14.

With this solution I verified that my Seachem Total Alkalinity test kit was right on the money. I also verified that my API alkalinity kit was reading 13% lower than what it really was.

Thanks again, Randy!

JimWelsh · Jan 28, 2015

Randy, do you have any opinion on what the uncertainty is when measuring volumes with the typical 5ml hobbyist plastic syringe?

Randy Holmes-Farley · Jan 28, 2015

No, I'm not sure, but I expect they vary a lot. On a short, fat 5 ml syringe, if someone is trying to read 3 mL, I'd be surprised if it is better than 5-10%. Long skinny syringes would be better. Some of the 1 ml types used in the hobby are like that.

I use long graduated hard plastic pipettes, which can be pretty inexpensive, but I've never bought one, just used freebies that the supply companies left at work for us to try.

UK_Pete · Jan 28, 2015

Randy are those the things that you dip into fluid, put your thumb over the top end of the tube, and then release your thumb to let the fluid back out? I was thinking recently of getting one of those pipettes that use a button but they seem quite pricey. Syringes are a bit cumbersome to me. If the simple tube things do a good job I've got a box of them I bought years ago, never thought to use them.

Randy Holmes-Farley · Jan 28, 2015

Yes, that's one way to use them. A suction bulb can also be used to draw fluid up, and some of these are fancy in allowing fluid to come out only when held open.

Pipette Filler