pH Controller

dw1305

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Hi all,
Link error
Sorry, worked for me because it was conversation with @Edvet and @ian_m, but it links into the <"question about ...."> chemistry thread.
I don't understand the chemistry, but I think the answer is that you are both right.

In soft water, without much carbonate buffering, any addition of CO2 will cause a large pH drop, but once you have more than ~4dKH buffering then you will always get a drop of approx. one pH unit when you have 30ppm of CO2 in the water.

I think this is because pH is a log10 scale and exponential data plotted as log10 values will form a straight line. You use a "4dKH" solution in the drop checker because the pH change is then matched to the colour change (protonation state) in the narrow range <"bromothymol blue"> pH indicator.
cheers Darrel
 
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Oldguy

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Gloucestershire, UK
bromothymol blue
Many years ago used to make my own close range universal indicator solutions based on BDH indicators. Died and gone to heaven when I got my hands on a pH meter. In those days the glass electrodes cost more than a weeks wages. Still have a Lovibond Comparator.

potassium bicarbonate
Good choice, I add a little to my tank on regular intervals.

The JBL drop checker
Good to know, perhaps if I am a good boy Santa will bring me one. Family despair about suitable gifts.
 

ian_m

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How easy is this JBL drop checker to read...whoops rather "over green"...luckily fish don't seem to mind...
upload_2019-3-26_9-33-47.png
 

dw1305

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Hi all,
Lovibond Comparator
You can still buy them for <"field work etc">.
In those days the glass electrodes cost more than a weeks wages
I think the saturated calomel electrodes are still better than the silver chloride type, but you have the mercury (Hg) issue on disposal, and the cost.

I'm still keen on buying an <"ISFET"> pH meter (again mainly for field work).

cheers Darrel
 

Oldguy

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Gloucestershire, UK
I'm still keen on buying an <"ISFET"> pH meter (again mainly for field work)
Canvas departments for any cash not spent. End of financial year is round the corner ;). To be serious analytical probes have gone from research papers to affordable routine equipment in the hand in a few decades. On balance still glad to be retired, though the pays not good.
 
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