If you've read my post on dosing Lanthanum Chloride you might be trying to work out how to drip dose. Dosing machines tend to have programs that work for periodical dosing and not constant dosing, so they are not great when it comes to the regular drip-drip style dosing you need for Lanthanum Chloride.
The best solution by far is to the regular hospital style drip bags and drop counter. This allows you to count drops, adjust the flow and calculate a dosing rate based on the frequency that the drops drip at, (or is that drips drop at?) Of course not everybody has access to that kind of stuff or else are impatient like me, and so need a DIY solution.
The solution to this problem is actually quite a simple DIY solution that can easily be made from those surplus bits and bobs you have laying around.
My DIY drip doser is made from an old ginger beer bottle. It has two holes in the lid with silicone tube. I used a glass bottle rather than something like a plastic drink bottle so that you could not accidentally squeeze it and overdose the tank.
One hole has a short length of silicone tube in it, this is the outlet. It should pushed in only far enough to make a seal.
Tip: The further into the bottle you push the outlet tube, the more solution will be left in the bottle
The other hole has a longer piece of tube in it that reaches all the way to the top of the inside and all the way to the top on the outside.. The outside end of the longer tube has a regular air line valve in it to regulate the flow. You can easily use this valve to dial in the flow to what you need. I have mine set to drip at about a rate of about 1 drop every 5 seconds.
Tip: The outside length of tube is longer to allow you tie it up and prevent it from falling into the water, which will stop the doser from working
The bottle needs to be inverted after you have filled it, you might want to do this over a sink or toilet the first time as it has a tendency to let a little 'squirt' out whilst the pressure differential inside and outside of the bottle equalises.
So how fast to dose? It's generally accepted that a drop is approximately 0.05 mL So you can use this value to help calculate your dosing regimen. Depending on what you are dosing, you may also be able to dilute it if you wish to dose slower than your valve will allow, or use a higher concentration if you wish to dose faster.
The amount I'm dosing with my Lanthanum chloride is relatively weak, so it would not cause an issue if the entire bottle ended up in the tank.
If you want to gain some confidence on whether your DIY doser works, just fill it up with tank water and set it dosing, then measure how long it takes to dose the bottle.