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Re: [APD] Using Sulphate of Potash in my tank


I would stick to the 44.88 percent K in K2SO4. I went back and looked at the link you first gave to your product. The MSDS sheet says: ?This product contains: Sulphate of Potash
Origin & Composition: Total Potassium Oxide (K2O) 48% of which 39.8%K is soluble in water
Classification: UN classification is non-hazardous?

I don't understand your fertilizer labels over there. The 39.8% you are using is really the wrong number. It is referring to the amount of Potassium Oxide that is soluble. The solubility of K2SO4 is 12 grams per 100 CC at 25*C. The solubility of K2O is listed as very soluble in cold water in my Handbook of Chemistry and Physics. The information on your MSDS sheet and fertilizer label is confusing.

If you use 302.832 / .4488 you will get 674.7 mg of K2SO4 to add to your 4 gallon tank to raise the K by 20 mg/l. The differences in your calculation and mine are really not significant if you are following the EI method of fertilization. Your idea of dissolving the gram of K2SO4 in a liter of water and just pouring out a fraction of it is an excellent way to get down to the mg level without a very expensive scale to weigh out small amounts. Good thinking!!!

Message: 2
Date: Sun, 21 Sep 2008 21:54:46 +0100
From: Stuart Halliday <stuart at mytriops_com>
Subject: Re: [APD] Using Sulphate of Potash in my tank
To: aquatic plants digest <aquatic-plants at actwin_com>

I believe Stuart Halliday wrote this email section below:
> I believe Jerry Smith wrote this email section below:
>> I have read different values for the percent of Potassium in Potassium
>> Sulphate, and I don?t understand why there are differences, unless it is
>> the purity of the salt. I have checked my math several times and don?t
>> find a mistake. Potassium oxide is 83.01 percent Potassium by weight.
> Thanks Jerry that all good info!
> With a 15L tank I'd better be careful how much I add...

So by your formula

A 4 US gallon tank to raise K by 20mg/l

4*3.7854 * 20 = 302.832mg of K

302.832 /0.399 = 758mg of K2S04

Therefore 758mg added to a 15L tank weekly should be enough?

If I add 1g into a 1L of water and only pour in 750ml, that should be near

Stuart Halliday
200 Million years in the making...

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