In message , Mike Lyle
writes
"Franz Heymann" wrote in message
...
wrote in message
...
On Mon, 19 Jul 2004 04:39:18 +0000 (UTC), "Franz Heymann"
wrote:

"jane" wrote in message
...
[...]
Franz, where on earth do you still get Benlate?

I still have a few leftover sachets from some which I bought a
decade
ago.
When that runs out, I will start using a more up-to-date fungicide.

Franz

You can say that again and again and again and ... :-)

Yes, indeed.
How does one know when a gardening chemical has passed its use-by
date?

Is there such a date with chemicals other than hormones? I'd have
thought that as long as they were kept dry, uncontaminated, and at an
even low temperature most would be stable. Is that a misconception in
the case of modern complex products?

It can be. Simple compounds tend to be chemically stable, thought they
may clump into a solid block harder to disperse or dissolve in water.

Some of them will absorb water from the air either through the packaging
or whenever the bottle is opened. This will tend to hydrolyse the active
ingredients and they lose activity. Most non-persistent pesticides start
decaying in concentration from the moment they are added to water.

Over long periods of time the water vapour from humidity in the air may
be enough to render old pesticides in part full bottles less effective.
Splash water accidentally into the stock concentrate container and all
bets are off.

Regards,
--
Martin Brown