Cheshunt Compound Shelf Life ?

I've heard of Macozeb, I thought that was actually Dithane, Dithane being its trade name.

I thought we were talking about a repacement for Dithane.

 

I can see where you are coming from. Its a bit of bad punctuation on the Jungle Seeds site. Its not "the new, Dithane alternative". But "the new Dithane, alternative." :D

Is it any good? it appears to be nearly as old as Copper Sulphate.

 

I was just looking on the JBA site and dithane 945 (blight control) has been withdrawn and a replacement is offered, I believe the this is the same product now for blight and damping off.


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http://www.bayergarden.co.uk/products/product.aspx?productid=188&categoryid=17

Steve...

 

Thanks Steve. I had a Google and found it was available in my local Homebase (just bought some). I presume it is fairly widely available now - I must have missed it because I didn't know what I was looking for.

Hopefully It will be as good as Cheshunt compound as it is also a copper salt.

 

Is it organic now Peter...or just less toxic than the dithane?

Steve...

 

I thought Cheshunt was copper based.:D

We appear to be going round in circles:D

 

Peter, pete , Steve
Thanks for the update on Cheshunt compound , according to the RHS you can use it until November this year, then it is banned. I presume "Murphys copper compound" will also be banned ? The Dithane replacement you found Peter is available in Wilkos etc . Does this now replace the Dithane 945 , I use for blight ?
Now for the science bit Peter your old tin of Cheshunt giving a PH of 1.5 (battery acid !) put the fear of god in me , as I have just mixed some and misted my Canna and Chili seeds with it this weekend. I brought some PH test papers home from work and tested my mix , one teaspoon to a pint - the Cheshunt compound I have is about 5 years old . The reading was PH 9 , which I hope is OK just being above the normal PH range of soils
Then again I may as well buy the new Dithane stuff , as I was going to bin my Cheshunt tin after this season anyway. But you know what it is like when you get that worm of a doubt in your head .

 

Steve.

I am sure its not organic on two accounts. Its not based on the chemistry of carbon, therefore its an inorganic chemical as far as chemistry is concerned. And I am sure its not a naturally occuring chemical, so the 'Organic' brigade can't use it. Actually they probably will.

Pete

You are right. I suspect that it is basically very similar to Cheshunt compound. I think its the copper bit that is effective. I believe Silver is even better - but more expensive :D. Perhaps they were just concerned that Cheshunt could produce sulphuric acid.

HarryS

Thats a really good clear chart - thank you. I did Chemistry along with Physics a very long time ago at Uni. So I have no doubt that my reading of pH 1.5 was in the right ballcourt - though I doubt my pH meter is very accurate being so cheap. It took a huge amount of added caustic soda to get it back to neutral. But I am still shocked at how it could be that bad. I did spray my seedlings with this very acid mix, and quite a lot have germinated and seem to be OK. So fingers crossed. I suspect that if the pH of old Cheshunt compound is still neutral it will work well irrespective of the age.

 

Any chance your pH meter has lost its calibartion? Chuck a coin in - its going to "froth" at pH 1.5 isn't it?

ALL my seeds that are in little bags with Chesunt-moistened kitchen paper, and mine is 3 years old or so. Not sure I have any Litmus paper or equivalent lying around. Ah! ... I wonder if the kids have a "blow up Science kit" or somesuch ... or will have to nick some from their school ...

 

I am sure my pH meter was roughly right Kristen. It gives 7 for tap water - which is correct. When I put it in the diluted solution it read 1.5. But I made up some more solution in a concentrated form and the needle went right off the scale. The purpose of the concentrated solution was to add NaOH solution to neutralise it and them dilute the mixture to the volume I wanted. I had to add a huge amount of NaOH. That alone told me it was very strongly acidic. Also the smell from the tin was quite overpowering.

Curiously, I did a lot of Googling and I came across a comment on another forum that said out of date Cheshunt compound could produce a pH of between 1 and 2. It was that comment that made me measure the pH of my own solution.

 

No simple explanation then. Blast! I'll have to expedite the acquisition of some Litmus paper then. Fingers crossed until then ...

 

Hi Kristen
Cheshunt compound should be blue and smell of ammonia. If it is both of these then it is OK to use.
Acids never smell of ammonia

Chemically, this mixture is stable and should last for many years if you put the lid back on

The politics are interesting -
It is being withdrawn from sale because it requires a european approval which requires tens of thousands of pounds worth of tests.
It is not in any major company's interest to pay for the approval, as Cheshunt compound is cheap, effective and easy to make. It is in direct competition with the expensive branded products but could be made by anybody with two cheap chemicals, a bucket and a stick.
Bayer et al must be delighted to see it taken of the market. Now you will buy their branded fine chemicals at 100x the cost

 

Hello Jim and thanks for summing up the Cheshunt Compound conundrum . Unfortunately the worm of doubt has made me dispose of my trusty 5 year old tin of Cheshunt and buy the new fangled Bayer solution. And , as you say , the legislation will increase every year so this will narrow the choice on many items so only the big players will remain.

 

Jim - thanks for your post, it has set me thinking again. This question has been nagging at me for some time - what I previously said just didn't seem to add up. I think I have confused myself and you in talking about an acidic solution. And I apologise.

Earlier it was suggested that the sulphate part from the Cheshunt compound could create sulphuric acid - which would indeed limit its shelf life, and I couldn't see any other mechanism that could be at work. The key test seemed to be to measure the pH, as sulphuric acid would have a very low pH. I used a cheap garden pH meter and indeed it showed a pH value of 1.5 - which set alarm bells ringing. And it needed large amounts of caustic soda to get the pH back towards normal.

However I have been doing some more research and I think I got it all wrong. The key lies in understanding what a pH meter does. pH is a measure of free H+ ions, There are lab pH meters which use a single thin walled glass probe and they are pretty accurate. However thin glass cannot be used in the garden, so a different mechanism is used with two metal prongs, which measures not pH but the small voltage associated with pH. So a garden pH meter is actually a variation on a voltmeter. I don't know exactly what is happening, but I think that a solution of copper and a probe of a different metal are creating a cell, which produces a voltage, which the meter assumes is a highly acidic solution. As a result adding caustic soda wouldn't effect the reading until the solution became extremely alkaline.

So I think that the pH meter was giving a totally wrong reading. I recently bought some of the new replacement fungicide which contains another copper salt - Copper Oxychloride, and this too appeared to give a very acid reading - but as a fresh purchase I knew that it couldn't be. I will try and get some pH test papers, which will give a much truer reading.

I have spent quite some time on the internet trying to research this. However I couldn't find a complete explanation of how a garden pH meter works, other than that is effectively a voltmeter. But what I did find out was how those soil moisture meters work. They don't measure directly the moisture content of the soil, but they measure the conductivity, which depends on the level of free ions. This means that if you put it in a glass of salty water (with plenty of free ions) it will record "very wet". But if you put it in a glass of de-ionised water, that you use to top up car batteries, because there are no ions it will record "very dry". So whatever the box says - you have to take it with a pinch of salt.

 

Harry

Don't knock the big players too much

There is a positive list, EC directive 91/414. If a material is not on that list, it cannot legally be used

Biocide manufacturers will have tested their own materials to ensure compliance. Some will be asked to test one or two generics for the good of the world, bordeaux mixture and copper oxychloride have been approved. This has no commercial benefit to the big player who tests it because anyone can use the approval.
No one has tested cheshunt compound
I have looked further into this and found that the active ingredient in cheshunt compound is approved http://sitem.herts.ac.uk/aeru/footprint/en/Reports/173.htm
But approval for the alkali filler ammonium carbonate (smelling salts) has expired http://sitem.herts.ac.uk/aeru/footprint/en/Reports/33.htm

Under these same regulations it is illegal to use a soap solution to kill greenfly. Not because soap is dangerous but nobody has bothered to approve it
BUT on the upside, a cowboy can never start making and selling a dangerous material, so we are all safer

Jim

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Peter
Now all becomes clear
These pH meters roughly measure corrosion potential and equate it to pH.
Two diffent metals and the voltage generated between them indicates pH. Higher voltage indicates higher corrosion rate indicates low pH
The problem here is that when you put a base metal (iron or zinc) into a copper soultion, then copper will exchange with it, plating out onto the surface. Electrically this is equivalent to massive corrosion or a very low pH
Bottom line is to get some emery paper on the electrodes before you trust the meter again
Jim