Thanks for that it is most helpful, which makes a change to the efforts of
others who have made comments.

I was under the impression that it was some sort of fertiliser, but it is so
long since I last used it I had forgotten how to use it.

Thanks again.

Alan


"Dave Hill" wrote in message
...
On 30 May, 22:09, "alan.holmes" wrote:
wrote in message

...

In article LGvMn.28769$9J1.20264@hurricane,
alan.holmes wrote:
As one does every 20 years or so, I can across a HUGE bag of something
called 'Phosphoric Acid' which I obviously bought for some use, but what
was
it used for?


SUPERPHOSPHATE
One of the standard fertilizer products, superphosphate was the first â
€œartificialâ€� to be produced in quantity. Rock phosphate and raw
bones were known to be sources of phosphate but this was present in an
insoluble or unavailable form.

Rock phosphate is crushed and treated with sulphuric acid to convert
it to the soluble form. By law the amount of phosphate in a product is
defined as % phosphoric acid and the statement must confirm its
solubility in water and other chemical reagents. A bi-product of this
process is calcium sulphate, which occurs naturally in gypsum.
Superphosphate produced this way is called single superphosphate
containing 17-19% phosphoric acid (P205), which is soluble in water.
It is typically prepared as a powder, but sources of this are drying
up in favour of triple superphosphate.

In agriculture triple superphosphate is much preferred being more
concentrated containing 44-46% (P205). This is achieved by treatment
of the phosphate rock with raw phosphoric acid, hence the higher
concentration. It is prepared as a prill or pellet which makes it
easier to mechanically apply to farmlands it does not contain any
substantial amounts of sulphur as single superphosphate does.

The primary use for superphosphate is in compound fertilizers, and the
fine powder form in composts. It is best applied in Autumn/Winter and
is most suitable for root crops. It is quicker acting then bone meal
and has a mild acidic action on the soil. Rate of use 2-4 oz./sq.yd.

Triple superphosphate is a more economical form being nearly 3 times
stronger and should be used with caution at 1-2 oz./sq/yd.

As with all phosphatic fertilizers do not over apply for fear that
excess will lock up trace elements.