# DIY solutions from dry ferts - grams/ml ratio?



## Mr Fishies (Sep 21, 2007)

I thought I'd be able to find this easily, maybe I'm feeding Google the wrong search words, but does anyone have a link to or know off hand how many grams of KNO3 or KH2PO4 can be dissolved in a given amount (ml) of water.

It's easy enough to calculate how to get X PPM of nutrient in 10ml of solution to make it easy to dose 3x/week, but I want to know how much can actually dissolve in 500ml of water.


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## Mr Fishies (Sep 21, 2007)

OK...should have waited a bit longer before posting.

KNO3 solubility at 20°C is 31.7g/100ml (or 31.6 depending on source). I only want a fraction that for KH2PO4 so I don't think that one matters.


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## jrs (Mar 18, 2006)

try this

http://www.csd.net/~cgadd/aqua/art_plant_aquacalc.htm


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## Mr Fishies (Sep 21, 2007)

Thanks JRS, I knew about Chuck's calculator and Fertilator etc. I calculated how much KNO3 in 500 ml to get the 10ml dose I wanted, but I could not seem to find how many grams would dissolve in a given amount of water. I didn't want to dump in the KNO3 and have 1/2 of it not all dissolve.


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## jrs (Mar 18, 2006)

If you plug in a very large number into the program a red warning will come up basically giving you the solubilty information.


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## Mr Fishies (Sep 21, 2007)

jrs said:


> If you plug in a very large number into the program a red warning will come up basically giving you the solubilty information.


I didn't realize it would do that...but there's a bit (OK a lot) of a discrepancy between what I found searching the web and what Chuck's' calc (software version) says.

My solution will be about 24gm/100ml so it may not matter, but Chuck's calc claims 85 grams/100ml in solution vs. 31 grams/100ml elsewhere?!


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## jrs (Mar 18, 2006)

Thats odd. Are both of the compared values at the same temperature?

Even at that 85 vs 24 is huge


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## jrs (Mar 18, 2006)

I just tried it and got the same answers as you. Must be a glitch in his program


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## Mr Fishies (Sep 21, 2007)

I was working based on this amazingly complete table from Wikipedia (I should have looked there first!) http://en.wikipedia.org/wiki/Solubility_table and I was using 20C as my assumed temperature. In order to dissolve 80 grams/100ml it looks like the temp has to be about 50C or so (chart doesn't show exactly). I wasn't planning on keeping my ferts heated!

Yep. I'd say there's a glitch.


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## Darkblade48 (Jan 28, 2008)

Definitely a glitch. I just checked the MSDS for KNO3 as well, and it's much less than the 85g/100 mL that Chuck's calculator reports.


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