I have used K2SO4. The stuff that you usually get at the nursery has a
fair amount of clay like material in it. Pure K2SO4 is a white crystalline
solid. When you mix the fertilizer stuff with water the K2SO4 dissolves
relatively quickly, leaving the clay to settle out with time. I'm a chemist
and out of force of habit I felt compelled to purify it. I mixed a cup of
the fertilizer grade with a quart of water and shook it up a couple of times
during the day, then I let the clay settle out overnight. I then carefully
poured off the clear liquid. You can also siphon off the clear liquid with a
airline hose and filter it with a coffee filter. I then condensed it down by
boiling most of the water off, reducing the volume to roughly two cups. As
it cools you should get pretty crystals to form in the bottom of your pot.
These crystals can be can be separated out if you want. I've added the
"dirty"stuff in my tanks with out too much clouding of the water. I use the
purified stuff with sulfuric acid to make pH buffer, works great.

Potassium sulphate will dissolve at 1 gram into 8.3ml at room temp. 1 gram
into 4ml of boiling water.

Let me know if you want help figuring out the math for your solution. You
may need to dose it in 2ml doses, because of the solubility limits.

Ross F.


"Mark Trueman" wrote in message
.. .
Group,

Is there anyone here who uses k2so4 in water to fertilise. I tried to
prepare some, first mixture couldnt get 8 tblspoons to dissolve in 400 ml,
reduced it to 4 tbsp but i still have to shake the bottle before i use it
as
it seems to separate after being left for a while.

Anyone else have this experience or any tips?

Ideally i wanted to be able to dose 1ppm K per ml of solution in my 160
litre. Currently i can only get .4 ppm per ml.

Mark