want to make a calcium standard...check my calculations please

[SDguy]

I have stock 1M Ca(Cl)2 in water.

110.99 g/mol. 40.08 of that is calcium. That gives me 0.04g calcium per mL of my stock solution.

1 ppm = 0.001 g/L

so

500 ppm = 0.5 g/L or 0.05g per 100mL.

If I dilute 1mL of my 1M stock into 80mL total volume { (0.04g * 100mL)/0.05g } I should have a 500 pppm standard, yes?

[bertoni]

That's looking close enough, I think. The conversion from mg/L to ppm is off by about 2%, if you care.

[SDguy]

What do you mean?

1 milligram in one liter of water = 1 milligram per liter or
one part in a million parts

I couldn't find anything going out more decimal places...

[bertoni]

http://reefkeeping.com/issues/2005-08/rhf/index.php#ppm

The article has more decimals. 1 ppm = 1.023 mg/L

[SDguy]

Ah, thnaks, that's what I was looking for...

[IndyReefMan]

Or, you could cheat and purchase a Seachem Ca test kit. It comes with a 425ppm standard.

[SDguy]

Virgo perfectionist freak...I prefer to make my own...

[Billybeau1]

Originally posted by IndyReefMan
Or, you could cheat and purchase a Seachem Ca test kit. It comes with a 425ppm standard.

I have tested Seachems standard and it only works with their test kit, which by the way tests about 70 ppm lower than other kits.

Gee imagine that. Make a test kit and then make a standard to match it so the consumer thinks it is accurate.

[SDguy]

Originally posted by Billybeau1
I have tested Seachems standard and it only works with their test kit, which by the way tests about 70 ppm lower than other kits.

That was my main concern...

[IndyReefMan]

Originally posted by Billybeau1
I have tested Seachems standard and it only works with their test kit, which by the way tests about 70 ppm lower than other kits.

Gee imagine that. Make a test kit and then make a standard to match it so the consumer thinks it is accurate.

What Ca test kit are you using? I've given up on Salifert.

[Billybeau1]

My Salifert Calcium test kit works just fine. If you want to verify its accuracy, pick up an API calcium test kit.

The only negative about api's is it tests in 20 ppm increments where Salifert gets you dialed in much closer. This seems to be unimportant to some.

My API matches my Salifert to a tee.

[mcneilwh]

Make sure you bake the CaCl2 to remove the water. Otherwise it will be light on Ca. Back in chemistry 101 we used Sodium Carbonate as a primary standard, after it was baked of course. You can make your own by cooking baking soda.

[mcneilwh]

opps that was for carbonate, no Calcium in that.

[IndyReefMan]

Originally posted by Billybeau1
I have tested Seachems standard and it only works with their test kit, which by the way tests about 70 ppm lower than other kits.

Gee imagine that. Make a test kit and then make a standard to match it so the consumer thinks it is accurate.

You're right! I bought the API test kit and it showed Ca at 500ppm. Seachem was reading 410ppm. And, I tested each twice , just to be sure. No wonder I couldn't keep my Alk up. I just bought that Seachem Ca test kit... what a waste of money!

[Billybeau1]

Yeh, I don't make this stuff up. Unfortunately it's true. At least from what I've tested.

Glad you got it figured out.