High Tide Aquatics

2-part chemistry/math help requested

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sfsuphysics

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Is there an easy way to measure the actual strength of a two part solution?

The way I figure, it's going to be extremely concentrated, so the easiest way would be to shake up your mixture, pull out a sample out (say 0.1ccs) then dump that into say 1000ccs of RO/DI water to dilute it by a factor of 10000, and then use an OTC calcium/alkalinity test kit to read what it should be. Now I realize that 1 liter would would probably dilute it too much, but will test kits for the aquarium work with freshwater for calcium and/or alkalinity?

I'm just curious because stuff like downflake gives a range of 77-80% calcium chloride by volume, well if you're dosing 1 cup (or whatever) of it constantly, those 3% variations here and there could potentially add up especially if they don't average out. Now I use calcium chloride anhydrous which is 94-97% by weight.. so I'd like to make sure I'm not adding too much (or two little) of my mixture to make one go out of whack way quicker than the other.
 
Use the Jdieck calculator:

http://home.comcast.net/~jdieck1/chemcalc.html

Set the volume to 1 gallon.

Set current calcium to 1ppm.

Set desired calcium to 401ppm.

You get 40.9ml of calcium solution to add to 1 gallon of water to give 400ppm.

Test with your usual test kit to compare actual to calculated.

I did just that the other week to doublecheck on my alk solution.

Also, if you are using a test kit that has a syringe for the titrant, stick one of the Salifert tips on it to get a more precise reading.
 
Ok, so tests kits will read from the solution itself diluted in freshwater?

And I don't have a salifert syringe, however the syringes I do have have tick marks to 0.01mL accuracy.. however I'm unsure what error that'll represent with what's in the tip of the syringe.
 
What Ca test do you use?

I use the Seachem one. It's one of the standard titration methods for Ca. I saw a writeup where someone used that method for titrating Ca in milk. Should be fine to test RODI or distilled with the added Ca solution.

Tap water might throw the measurement off a little if it has high TDS.

The titrant left in the syringe tip doesn't matter. You're taking the delta of 2 readings on the scale. The only thing that matters is the start and stop readings as long as you don't need to refill your syringe.
 
But you will only have resolution down to the size of the large drop, not .01 ml.

Unless you try to cheat and get partial drops out of the syringe.
 
Ok, just checked the syringe.

With the Salifert tip, the drop size is ~.02 ml.

Without the tip, the drop size is ~.05 ml.

On my Ca test, .05 ml corresponds to 25ppm.

Salifert tip will let you get within 10ppm. I do half drops with the Salifert tip also.
 
.05ml corresponds to 25ppm in the concentrated solution? But how much did you dilute it? Did you put one .05mL drop into 10mL of water?

My Ca test kit reads 20ppm at 5mL, so would need to kick it up to 10mL to give a 200:1 ratio of dilution... urgh.. ok it's too early in the morning for me to think much math, I'll stick to kakuro this early.
 
I meant that for my kit, every .05ml of Calcium titrant used corresponds to 25ppm Ca in the test sample.

So if I use .80ml of titrant, my water sample had (.80/.05)(25)=400ppm Ca.
 
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