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4dkh Drop Checker DIY?

GlenD

Member
Joined
26 Jun 2019
Messages
168
Location
London
So I've run out of my drop checker solution.

Is the below correct?

  1. Add 6g of sodium bicarbonate (NaHCO3) to 500ml RO = 500ml of 400dKH solution.
  2. Then dilute 5ml of 400dkh solution with 495ml H20 to get 500ml of 4dKH solution?
  3. Take 5ml of this into drop checker and add 5 drops of my AP PH test kit?
Questions...
  1. is the above correct?
  2. if I wanted more than 5ml of the 4dkh solution in my drop check i.e. 5ml, would I need to add another 5 drops of the API PH tester?
  3. if you add more than 5 drops of the API PH tester will it give an incorrect reading or will it just make the colour darker?
Cheers
Glen
 

dw1305

Expert
UKAPS Team
Joined
7 Apr 2008
Messages
12,078
Location
nr Bath
Hi all,
Is the below correct?
  1. Add 6g of sodium bicarbonate (NaHCO3) to 500ml RO = 500ml of 400dKH solution.
  2. Then dilute 5ml of 400dkh solution with 495ml H20 to get 500ml of 4dKH solution?
Yes, I think it is.
take 5ml of this into drop checker and add 5 drops of my AP PH test kit?
You need "bromothymol blue" as the pH indicator. It is a narrow range pH indicator (colour change below)
picture_1-png.png
if you add more than 5 drops of the API PH tester will it give an incorrect reading or will it just make the colour darker?
Just add enough bromothymol blue so you can see the colour change, it won't be very many drops.

I just had a quick look (on a well known auction site) and a 35 mL bottle of bromothymol blue is £6.

cheers Darrel
 

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