Fertfriend TMG verification (for Laith and whomever)

[Wet]

From quenton's calc thread.

For 55g of water volume, the calculator indicates 38ml of TMG per week (or 33ml without the EI option ticked) to aim for a target level of 0.5mg/l of Fe...

The TMG calculators I've seen online (for example: http://www.fishfriend.com/fertfriend.html) indicate that 38ml of TMG will add 0.133mg/l of Fe (and 33ml will add 0.115). Is that calculation wrong?

FertFriend is functionally correct.

I have to brush up on php for work, so put together a calc to verify. I used this page's percent solution equivalents to veify conversion from percent solution to g/100mL:
http://antoine.frostburg.edu/chem/senese/101/solutions/faq/dilute-percent-to-ppm.shtml
and
http://homepages.gac.edu/~cellab/appds/appd-a.html
(first two on a google search)

This also coincides with Steve Pituch's mysterious *10 constant in the solution formula on his computations page.

% solution = grams/100mL
TMG is .07%Fe = .070g Fe/100mL = .7mg Fe/mL

.7mg Fe/mL * 38mL dose / (55gal * 3.785L/gal) = .128mg/L Fe

Here's my online calc. It rounds to three sig figs:
http://justanothertank.com/calcs.php#TMG

Please correct me. If anyone wants my php code just ask.

edited: spellin'

 

[Wet]

Re: Fertfriend TMG verification (for Laith and whomever)

Hmmm. MyTMG says "W/W% (Gew./Gew. %, P/P%)" and lists mass for volume. W/W means weight over weight, not weight over volume, so this means the percentage Fe listed is calculated from mass?

From TMG bottle: 250mL = 260g
TMG = 1.04g/mL = 1040mg/mL

mL dose * 1040mg/mL * .0007mg Fe/mg TMG / (tank gal * 3.785L/gal) = Fe ppm

38mL * 1040mg/mL * .0007mg Fe/mg TMG / (55gal * 3.785L/gal) = .133ppm Fe

Indicating FertFriend is correct and my using percentage of solution for mass/volume above and on the calc is incorrect.

Yes?