Don't forget the additive effect of the dilution glassware. In your How-to post you advocate graduated cylinders - that probably adds 1% error for each time you use one (50 ml diluted to 500ml = 2%). You could reduce the error greatly using volumetric glassware (pipet and flask) for the dilutions.>>>Hoppy
What is your estimated error range for these solutions? 4 +/-? dKH. <<<
The lab certified alkalinity standard pretty much speaks for itself.
The sodium carbonate at 99.5 % purity so you could have a .5 % error.
If the baking soda is 97% pure you might get a 3% error.
From what I have read the typical error of an alkalinity titration test kit is 5 -10% so I don't think you would see the error of the standard anyway.
Yep, Chemistry - not biology though. My thought was regarding the shelf life - it would seem 500ml would last a long time if you only need it for one or two drop checkers - replacing once a month or so.I keep deionized water in 5 gallon buckets for my reef tank (it's only a 29g tank). I had a bucket of deionized water left in my garage in Texas for a couple of months during the summer and it never had any mold in it.
I wasn't planning on adding anything to the KH Standard but I was interested in what Kevin had to say. I looked at his profile and it said he was a chemistry professor.