How Do You Produce PH Buffer Solutions

I was wondering if there is a chemist in the house?

Me  Though my degree is rather old now, and I've forgotten most of what I knew back in the 1970s.

The problem with pH is the scale is logarithmic not linear. pH is the reciprocal of the logarithm of the concentration of hydrogen ions. So pH 7.0 is 10 x pH 6.0.
To be honest, anyone who doesn't like the colour charts would be better off buying a pH meter. It would probably be cheaper than a colorimeter.

Buffers from first principles here. Good luck

I really like what you're doing with this sort of stuff, Andy. Keep it coming.

I use a pH meter that cost just a few pounds from EBay. Last year, I worked with a consultancy that used one that they had bought for £200+ from a scientific instrument supplier. Our results were exactly the same.
Trying to make a whole range of buffer solutions and using a colourimeter seems to me like a lot of effort when a cheap pH meter gives you a direct readout simply by dipping it in the tank.

Thanks for the heads up Colin, sounds like you have connections in the sleazy world of class A street buffers  Trust me, I won’t be upsetting you in a hurry.

Perhaps I have been unlucky but I thought had a really good pH meter from Extech, it had a good write-up, very good spec, replaceable probes and could accept other probe types to measure ORP as well. So my logic was that it should have out-lasted the probes that don't live forever, I wouldn’t have to buy test kits and it would more importantly be more accurate as I was injecting CO2.
Within a week of getting it the pH reading started constantly cycling 0.3pH in the calibration buffer. That was in Jan of this year, I'm still trying to get my money back. Grrrrr !
If anybody is thinking of buying stuff from Armco or Air concern JUST DONT !! Their tech and customer support royally stinks and I have 59 (and counting) Emails to prove it.

I'm not sure about the costs of the materials, you may be correct but in many cases a kg of lab quality chemical (Colin, that's 'gear' in your circles) is very cheap. Plus half the fun for me is the learning process, and yes I am aware that this is weird.

The way I justify it to myself is as follows.
A pH probe always has to be calibrated at two points and fairly regularly - at least monthly therefore buffer is a consumable item at about £20/litre and you need two buffer solutions. My calibration curve would be a one time job and once I have it the software just loads it into the colourimeter each time I do a test.
The only thing a colourimeter does is to replace the human eye when it comes to reading the colours. Once it knows the relationship between the sample colour and pH from the calibration curve it is many times more accurate than the eye and the stupid colour cards that test kits provide. [The scraping sound you hear is me getting my test kit colour card soap box out - sorry]
I now get repeatability between NO3 tests (different water samples from the same tank) within 2 or 3ppm. I absolutely know it’s not important for NO3 to be that accuracy, but it’s the test I do most regularly so I have the most experience and can quote numbers. This compares to ‘Hey Pet, what do you think this is 40 or 80ppm?’ with a card.
It always seemed strange to me that in the case of Ammonia the rule is ALWAYS ZERO yet my kit starts reading at 0.25ppm and goes up to 8ppm ! - where 0.5ppm is said to causes stress and harms fish. On some of the cards it’s hard to see the difference between two colours or as you open a new pack you notice a significant difference between the two. This just seems wrong to me and devalues the test kits.
My last Ammonia test was 0.07ppm and I would be confident that if I retested the same water I would be within a couple of hundredths of a ppm of this reading, with this resolution I can spot a problem well before it affects the poor blighters in the tank.
Yes I hear you shout, but this would read zero on a card. True I would shout back, but only if the card colour match is correct, and then we all go off in a big huff

Sorry this went off the pH topic a tad.
Regards, Andy the weird minion.

Andy, just a thought I should've thunk a while ago.

A colourimeter is for testing density of colour (which is great for nitrites, nitrates etc) or for colour end points (like GH and KH), but pH is a colour change rather than a gradually increasing density of one colour. So, my postulate would be; is a colourimeter a suitable instrument for measuring pH?

Answers on a postcard to the usual address, please.

I'm kind of confused why you'd need such accurate readings, unless you're keeping an especially delicate fish.

ColinB,
I was just looking at your link again
http://delloyd.50megs.com/moreinfo/buffers2.html
Then I noticed the company name in the top line. Oh my! I'm looking as shocked as your avatar.
Perhaps they have a range of suppositories ?

mmmm - a very poor choice of product name. Puts a whole new meaning on 'product placement'!