On Thu, 19 Jun 2003 23:26:51 -0400, Greg
wrote:

1/10 teaspoon in 75 gal - 1.18ppm
2ml of enema in 75 gal = 1.08ppm

Is this correct or am I an idiot?!

Short answer: Yes, this is correct.

Long Answer:

Well, I've never dosed phosphate using the fleet enema, but here's
some calculations I did for someone who emailed me with a similar
question.

Note: The person who I was emailing had said that the Fleet enema
contained 118ml of solution containing 16 grams of monobasic sodium
phosphate and 7 grams of dibasic sodium phosphate. This is slightly
different than your statement of 19g and 7g. Which is correct?
You'll need to adjust the calcs below if the 19g is correct instead of
the 16g.

-------------

monobasic sodium phosphate
Molecular formula: H2NaPO4

dibasic sodium phosphate
Molecular formula: HNa2PO4


The molecular weights involved a
H : 1.00794 g/mol
Na : 22.98977 g/mol
P : 30.97376 g/mol
O : 15.9994 g/mol

(monobasic sodium phosphate)
H2NaPO4 = 2 hygrogens, 1 sodium, 1 phosphorus, 4 oxygen.

when you add it up, 1 mol of H2NaPO4 = 119.977g. Phosphate (PO4) =
94.97136 g/mol. So, 79% of the weight of H2NaPO4 is phosphate.

(dibasic sodium phosphate)
HNaPO4 is almost the same, just missing one hydrogen
1 Hydrogen, 1 sodium, 1 phosphorus, 4 oxygen.

1 mol of HNaPO4 = 118.9691g. So, 80% of HNaPO4 is phosphate.

118ml, containing 16 grams of monobasic, and 7 grams of dibasic.

So, in 118ml, you have 12.64g of phosphate from the monobasic,
and 5.6g of phosphate from dibasic. (79% and 80%).

So, in 118ml, you have 18.24g of phosphate.

Each ml would then contain 0.155g of phosphate, or 155mg.

---------------------------------------

So, to find out if 2ml of enema in 75 gal = 1.08ppm:

2ml would be 310mg. 310mg of potassium in 283 liters = 1.09 mg/l or
1.09ppm.

And yes, 1/10 of a teaspoon in a 75g would be 1.18ppm.





Chuck Gadd
http://www.csd.net/~cgadd/aqua