hooha

Do you mix up a "fresh" batch of buffer solution every change? Or can I mix up 100ml at a time and store it for a while?

Naja002

A DIY HOB Drop Checker and pH Controller from Sept. '92:

The Krib

HTH

hoppycalif

Don't be misled by that article. You can't hang this on the back and have part of it outside of the tank and part inside. If you try that you will get a difference in temperature between the tank water and the drop checker water, which will cause slow distillation of the warmer water to transfer water to the cooler water, changing the KH of the reference water. Also, it doesn't work with tank water in place of KH reference water, and it reacts so slowly to changing tank water conditions that it is useless as a pH controller or a CO2 controller.

If you make up a bottle of KH reference water, and seal it tightly, it should be good for several months at least. Since the indicator solution is a dye it can't be completely stable, so if you add the indicator solution to a bottle of reference KH solution, at least do it in a small bottle, and store it out of direct light. Don't forget that some plastic bottles allow water vapor to leave the bottle very slowly, which would change the KH of the water. (Store a plastic bottle of water for a couple of years and it starts to collapse.)

u2_crazy

This has been a very good thread, long however.

Anywya, I consider myslef pretty new to the CO2 injection and am at a point where I have to decide where to go with CO2.

Some questions I have about this CO2 dropper is:
1. The red sea model looks nice and appears to be pretty cheap, is it recommended for those that aren't creative enought or have the time to DIY?

2. The KH and the Distilled water, how do you test it? I have a test strip kit but not a liquid test kit for KH. If I mix a mason jar worth, would the water last?

3. how often do you need to refill the dropper?

4. If I go with the red sea, once the reagent runs out, can I use normal PH reaent from my AP test kit? do you use the high range or low range ph indicator?

Naja002

Hi Hoppy,

Glad You realize these things straight-away. I didn't put much time or thought into the article--just thought I would share it and see if it had any value. Thought that it might have been a "Lost Technology" I got the link from a recent thread here at APC.....

hoppycalif

The Red Sea model will work as well as any of them. The principle this works on is so simple even crude DIY units work fine. In my opinion the only advantage of the glass ones is that they look nice in the tank.

You can mix the KH solution without a test kit, but then you need a digital balance that will measure accurate to +/- .01 grams, and a volumetric flask that will measure at least a liter of water accurately. If you mix 4.99 grams of bicarbonate of soda that you have baked at low heat for several minutes to dry it out, with 5 liters of distilled or DI water, you will have 5 liters of 40 dKH water. Then mix 10 ml of that with 90 ml of distilled or DI water, and you will have 100 ml of 4 DKH water. This should be more accurate than depending on a test kit, and you can store both the 40 dKH and the 4 dKH solutions in airtight bottles for an indefinite time.

You can use the reagent from any pH test kit, if the kit gives yellow at about pH=6 and blue at about pH=7.2.

The solution in the drop checker will last at least two weeks, with no problems. But, eventually you will need to clean off the "biofilm" on the drop checker, and add fresh solution to it.

claire09876

Hello,
I'm very new to all this. I'm not sure what you mean by distilled water for your drop checker and why that's important. Could you explain please? I'm assuming from your discussion that you can change the KH of this by adding bicarb of soda. KH is the water hardness right?! So it will be very different depending where you live in the counrty (I'm in the UK).

Sorry new to website and didn't realise there was more after 1st page!!!! Maybe there are answers in the other 19 pages!!!! Sorry if I have interupted your discussion on something else.....can I delete an entry and how?

Thanks
Claire

Squawkbert

You use distilled water to make your 4dKH solution. If you use plain water, pH could be off as a result of something other than the bicarbonate.

PS - for you "real chemists" 4dKH corresponds to 0.06648mM Na Bicarbonate (if my math is right).

hoppycalif

I have a workable, DIY, easy to make design now for a membrane version of the drop checker. Tomorrow I will make a couple to do some more testing. Here is the sketch:


This design will allow you to reduce the thickness of the KH water solution to as thin as you can use and still see color differences, thus making it react rapidly. It also will seal well, so leakage of the solution will not be a problem. And, you can use either Tyvek or Cole Parmer membrane, or just about any other membrane on it. Installing the membrane will be as easy as I can make it be. All of the materials are readily available from a Tap Plastic store (clear acrylic tubing) and a hardware store (for O-rings), plus a 1/2" diameter probe holder/vacuum cup from the LFS. I feel good about this one!!

This is a result of a lot of experimenting I did and reported on the Barr Report, see: Gas Permeable Membrane Drop Checker - Barr Report

To explain this some more, the top O-Ring is to seal the drop checker fluid in the chamber (the blue green color on the sketch), and the bottom O-ring is just like a rubber band to hold the membrane on the device. I know from testing that if the thickness of the fluid layer is only around 1/16 inch this will react in less than an hour, probably less than 30 minutes. I haven't tried to make the checker solution strongly colored enough to go below 1/16 inch thickness, but it would be worth trying it thinner, to see if a 5 minute response time is achievable. I expect to be able to make one of these in less than 30 minutes with hand tools.

Squawkbert

Nice - I've been playing w/ some different membranes that are more commonly available (no luck yet).

Please post some part numbers or specs for the membranes you've got working!