# 4DKH Referance solution DIY



## AverageWhiteBloke (1 May 2010)

I was thinking off knocking a batch up and wondered what the people here do for making their own solutions. Any tips appreciated before I have a go?

I was going to use the method off here http://www.plantedtank.net/forums/gener ... d-how.html or has opinions changed on the best way to do it?

I can get 5ltrs of distilled water from Halfords for Â£3.69, has anyone used this before? I do have an API de-ioniser which I haven't used for years so I'm not sure what condition the resins are in and will have probably perished by now.
I was only thinking of doing the link method because it means I can get away with 1x5ltr bottle, the method on James would need slightly more than 5ltrs.

Does the ref solution work ok with the orange type ph solution as well as the bromo blue? I got some with my drop checker but I already have AE bromo/4dkh mix and haven't used it so would like to try this and compare the results.


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## Dolly Sprint 16v (1 May 2010)

AWB

Hope this answers your question:
viewtopic.php?f=37&t=9276&hilit=+4dkh

Regards
paul.


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## AverageWhiteBloke (1 May 2010)

Thanks it certainly did, it makes me wonder why you don't just put the 0.12g straight into the litre but there must be a good reason possibly with the quantity being so small there's more room for error.
Have you had any experience with the orange PH fluid?


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## Dave Spencer (2 May 2010)

AverageWhiteBloke said:
			
		

> Thanks it certainly did, it makes me wonder why you don't just put the 0.12g straight into the litre but there must be a good reason possibly with the quantity being so small there's more room for error.



Exactly.




			
				AverageWhiteBloke said:
			
		

> Have you had any experience with the orange PH fluid?



You need Bromo blue. For the orange indicator to work, you will need a reference solution at a different dKH.

Dave.


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## AverageWhiteBloke (2 May 2010)

Thanks Dave, do you know the dKH needed to make the orange fluid accurate? I know it's probably best practice to buy the stuff ready made but I already have the PH fluid and I usually only order stuff when I need a few things to keep delivery charges down.I don't want to just get this sent if I can make something up costing tops Â£4
I've been searching for the answer on the right dKH but get conflicting views, some people even saying that even though it is orange it's still Bromo blue which I can't see being true.


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## Dave Spencer (3 May 2010)

AverageWhiteBloke said:
			
		

> Thanks Dave, do you know the dKH needed to make the orange fluid accurate?



Sorry, I can`t off the top of my head.



			
				AverageWhiteBloke said:
			
		

> I know it's probably best practice to buy the stuff ready....



Not necessarily. I make mine because I have access to very pure water, extremely accurate scales and a lab. Having said that, 4dKH doesn`t need to be overly accurate, as it is still just a general indication at the end of the day.

The orange stuff is not Bromo blue as far as I know (maybe the name could be considered a smoking gun). I have some that came with a drop checker, and it doesn`t work.

Dave.


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## AverageWhiteBloke (8 May 2010)

The stuff that came with my DC doesn't appear to be working either, it does go blue but never raises even when I know for a fact there is enough CO2 in the column to at least get a greeny/blue. 
This could possibly be down to the 4dKH being out although I have tested this to within 1/2 degree. Does anyone know what dKH the reference fluid should be when using the orange ph fluid as oppose to Bromo? I can't find anything about it I always end up back at 4dKH.
It seems that a lot of the DC manufacturers are using this fluid instead of the Bromo so would be handy. 
Another possible stupid question is Bromo blue just Bromo blue, for instance would the stuff used in aquarium test kits be the same make up as the stuff you can buy online through chemical manufacturers? I saw a place selling 0.04% Bromo Â£13.68 for a 500ml bottle.


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## Dolly Sprint 16v (8 May 2010)

AWB

My Co2 reagent is green in its colouration and once mixed with the 4dkh sloution it turns blue, then depending on co2 levels within the water it either stays blue or goes through the colour change to lime green when submerge, if I remove the dc and observe the colouration against a white back ground its yellow.

The only time that I see blue is directly after a water change when there is very little or no co2 within the water column.
Regards
Paul.


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## ceg4048 (8 May 2010)

Hi,
    Bromothymol blue is only blue under alkaline conditions. Otherwise it's a yellow substance. Any pH test kit or any source of the substance can be used. Under acidic conditions it turns yellow. 

If you want to test your Bromothymol blue then it's not a good idea to depend on your CO2 because your assumptions about your CO2 could easily be false. Take a few drops of any acid and test it with the Bromothymol blue. Vinegar is an excellent way to test the reagent because it is a weak acid, just like the Carbonic acid you are attempting to measure in the tank. Vinegar is safe to use while still being an accurate indicator. If the Bromothymol blue solution turns yellow when you add vinegar then you know that your assumption regarding your CO2 is not valid.

Cheers,


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## GHNelson (9 May 2010)

Hi Guys @ukaps
Did a bit of trawling on the net.
Ive been trying to find out what the Orange/Yellow Co2 indicators are, which are supplied with various drop checkers.
I found this quite interesting,and informative.
http://www.funsci.com/fun3_en/acids/acids.htm
Scroll down to The Acid Base Indicators.
Have a read of this link also  http://chemistry.about.com/library/weekly/aa112201a.htm
Regards
hoggie


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## AverageWhiteBloke (9 May 2010)

Very very interesting stuff, talk about not seeing the wood for the trees never did it occur to me that Bromo blue wasn't actually blue until mixed with an alkaline substance   
I fine tuned my 4dKH solution today, it was turning more on 4.5 so I added some de-ionised water in 20ml increments until the KH reacted bang on the fourth drop. I then added 2 drops of the indicator fluid that came with the DC which gave me a better reading of about 7.2 on the colour chart that came with it. Before the blue colour was a lot deeper this actually looks a lot loser to the commercial 4dKH+Bromo that I bought, as suggested I added 1 drop of vinegar and it immediately turned yellow so I'm pretty safe to say that it's working.

Yesterday I put in a fresh DC with AE 4dKH+Bromo and this morning it was green, I'll try with this new one again and see what colour I get in the morning all being well I should get a result I will let you know how I get on.

Before anyone comments on why I am doing this if I have some commercially working indicator already it's just because I wanted to   I'm glad I did I have learned so much just from this little experiment and I have a lot better understanding of Co2 and DC's in general. I have enjoyed it, makes me wonder why it didn't do this at school I could have had a job I actually enjoyed.   It's no longer just a thing that changes colour and looks nice in my tank.


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## GHNelson (9 May 2010)

Hi
hoggie here
I'm also interested,because I've got about 7 bottles of Co2 DC solution lying in box in various colours, that came with the drop checkers from Orange and Green also Blue that don't work with 4Dkh fluid.
So a little experimenting may be on the horizon.
Cheers


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## dw1305 (9 May 2010)

Hi all,


> Take a few drops of any acid and test it with the Bromothymol blue. Vinegar is an excellent way to test the reagent because it is a weak acid, just like the Carbonic acid you are attempting to measure in the tank. Vinegar is safe to use while still being an accurate indicator. If the Bromothymol blue solution turns yellow when you add vinegar then you know that your assumption regarding your CO2 is not valid.


Is a very good answer to testing whether your indicator is working, it may take a few minutes for the colour change to occur.  

I can't think of another orange indicator that changes colour over the right pH range, it may be a "universal indicator" solution that would be much less accurate, but cover pH4 - pH11. They are cheap to buy, but I don't think you can DIY them.
Via that unimpeachable source "Wikipedia":
 "A universal indicator is typically composed of water, methanol, propan-1-ol, phenolphthallien sodium salt, methyl red sodium salt, phenol,4,4'-(3h-2,1-benzoxathiol-3-ylidene)bis2-bromo--methy l-6-(1-methylethyl)-, s,s-dioxide, monosodium salt, and phenol,4,4'-(3h-2,1-benzoxathiol-3-ylidene)bis5-methyl2-(1-m ethylethyl)-, s,s-dioxide, monosodium salt. "

cheers Darrel


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## AverageWhiteBloke (9 May 2010)

The one I got with my Chameleon DC looks red in colour when dropped on white paper, out of curiosty how come the neutral colour is blue which means a ph of 7.2? I would have thought it would be 7.0 which is green. I need my 3dkh tank to be at about 6.7>6.8 for optimum co2 but does that mean a green DC is at 7.0 going off the colour chart supplied?


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## ceg4048 (9 May 2010)

It's not clear exactly what reagent or combination of reagents are being used in any particular test kit. One thing is for sure though - just because your dropchecker is at optimum colour it does not guarantee that your CO2 is optimal. It's not that simple. Use the dropchecker as a guide and don't be mesmerized by the colours. The dropchecker shows you the path, it's not the letter of the law. 

Cheers,


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## AverageWhiteBloke (12 May 2010)

> The dropchecker shows you the path, it's not the letter of the law.



Point very much taken cheers.   
Just as part of my experiment I tried different combinations with a spare DC and some different indicator fluid I had lying about.


They had both been in the tank for 24hrs and are pictured still in the tank using a white ruler for background. The upper DC contains my own 4dKH mix with the indicator that came with the DC from Chameleon, the lower AE 4dKH+Bromo mix.
The type of DC is not the issue as the colour never changed when in the other glass type being the reason I did this.



On this test both been in the tank 24hrs again but this time the upper has my own 4dKH mix with 2 drops of Red Sea long term indicator in and the lower same AE stuff. Picture took at the same time of day with tank lights off. Like a few people have already commented the AE stuff is quite hard to get a reading off when still in the tank but out of the tank its is actually a bit greener than it looks.

Conclusion

Using the law of averages 2 to 1 as well as using normal ph tests there is a chance that the free indicator solution is the problem here. Both indicators went green whether it was my 4dKH fluid or AE's and my ph using electronic and dip test both had 6.7 to 6.8 in 3dkh tank water.  That's not to say the free one does not react to acids as proved in the vinegar test which it does but it doesn't seem to react to safe co2 at levels commonly used in a planted tank. Maybe as previously mentioned the solution it works in may not be 4dKH this I don't know.

The reason I thought I would mention this is being a noob myself, I know when getting started most people when embarking on diffusing co2 and using DC's their first stop is ebay to get a cheap glass DC. The indicator fluid that comes with it might not be the most accurate and for some people can get them off on the wrong foot right from the start. I was lucky enough to have others to compare it too and decide which was giving me the most accurate reading.

I just thought it was worth mentioning hoping it will stop somebody's head going round in circles   As mine did.


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