Chempak fertiliser precipitate/insoluble component

[el48tel]

Having read all of the above, I'd suggest that it's probably the phosphate component precipitated out with calcium from hard water. No amount of boiling and stirring and adding extra water will get that to dissolve since it's insoluble ... as in the stuff bones from which bones are formed. The chemical calculations I will not include here.
The correct volume of liquid at the time of making the solution is needed to prevent the precipitation. Rain water is a better idea than tap water but only if it's collected off glass and not run over the limestone chippings often found on flat roof constructions.

[DavidH]

Interesting - will have a go mixing 2g in 1l of deionised water and see what happens.

[iann]

I have very soft tapwater and I've also tried many times with rainwater, and I still get a small amount of stuff that doesn't dissolve from #8, so a calcium precipitate seems unlikely. Different ways of mixing don't seem to solve the problem. This stops me using it with my fine rose because it clogs.

[el48tel]

Since many of the specialist fertilisers contain trace metal components like copper, they need to stop these from dropping out of solution especially if the pH or the alkalinity is out of the "normal". This is normally achieved by adding chelating agents like EDTA and buffer agents to correct the pH. These also will swap the copper for calcium under certain conditions so that the calcium is held and the copper drops out of solution. If the calcium concentration is high it will preferably precipitate with the fertiliser phosphate .... ie if you try to make the solution more concentrated than normal. Been there and done that with the same outcomes as described .... the calcium dropped out of solution as the phosphate compound.
Liquid concentrates like Tomorite don't tend to drop the phosphate when they hit water with high alkalinity but their nitrogen content is very very high.

[Chris L]

I've noticed it too. Could it be something inert used to add bulk to the fertiliser?

[el48tel]

Wouldn't have thought "inert" in the material. That would be costly and increase the weight without increasing the "value added" of the product yet decreasing it's effectiveness. Manufacturers don't do that.

[iann]

There is relatively little insert material in most of the Chempak formulae. If you add up the NPK, their non-NPK components, and the trace elements then you've pretty close to 100%. It looks for all the world like it should dissolve completely, but there's always something left over.

[Chris L]

Wouldn't have thought "inert" in the material. That would be costly and increase the weight without increasing the "value added" of the product yet decreasing it's effectiveness. Manufacturers don't do that.

When I worked in a chippy years ago I always remember that they had big gallon bottles of washing up liquid. They used to stand under the sink. Anyway on a few occasions the owners bought bottles with an extra 10% in a slightly bigger bottle, which didn't go under the sink.

So what I used to do was keep some of the standard containers and fill them up from the bigger bottles with the extra 10% in. Every time the liquid in the +10% bottles was less viscous than the normal bottles. [In other words it was watered down.]

I can easily see a manufacturer of a powdered product adding bulk to make the expensive part of the product last longer when they are packing it in boxes.

Tip a box of cornflakes (or something similar) out of it's box to see if it is full of only complete flakes......

[el48tel]

Yes dish detergents are often thickened because you only need a very low percentage of the surfactant to operate ...
and yes the el cheepo is frequently watered down so their big bottle at the same price is mere smoke and mirrors.
As for breakfast cereals ... they are packed to settle in transit and the void filled with an anti-humidity anti-oxidising atmosphere.

[DavidH]

Have just dried out the non-soluble residue from when I dissolved 50g of champak No8 in 1l of tap water – the result is around 1.5g of white powder, I assume its Calcium phosphate?
Local tap water is started to be 1.04 mmol/l of Calcium carbonate.

Have just mixed 2g of champak No8 in to 1l of deionised water, is again an insoluble component.
Hard to tell is its less than the 60mg seen in the tap water or not – but does seem there is still a component that ether does not dissolve or is precipitated out even in deionised water.