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Anyone tried used etchant as stump killer?

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Hero999

Banned
Someone (Krumlink I think) mentioned that he spilt some Used Ferric Chloride on the lawn and the grass wouldn't grow for years after.

I've decided to put the herbicidal properties of copper to good use. I use Sodium persulphate / sodium bisuphate PCB etchant solution. The used solution is a mixture of sodium sulphate (I think) and copper sulphate, the latter I know is harmful to plants.

There was a 25 year old laburnum tree in the back garden that needed removing, these trees are nice but we've already got one but it spreads like a weed.

I chopped it down, drilled loads of holes in the stump and filled the holes with the used solution. It's been a few days and I can't see any signs of regrowth but I think I'll have to wait until spring next if that happens, hopefully it's gone for good.

I've covered it with a bucket, in the hope that it'll stop the rain from washing the etchant away.

One disadvantage might be that copper is anti-fungal so the stump probably won't rot very well.

I've noticed another funny thing: it reacts with the soil, I don't know why. I've test it with chalk and it didn't react (the soil is clay chalk where I live), I tested it with potting compost and it didn't react. Any one know why it fizzes and gives of a horrible gas when mixed with clay?
 

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Blueteeth

Well-Known Member
Wow, you must really hate that plant. I guess the sodium sulphate wouldn't do 'nature' much harm, since theres plenty of sulphates in the soil anyway, but I imagine the copper sulphate would stop that thing from returning. - Or anything else.

Updated:

I posted some long schpeel about calcium carbonate, but I noticed you already tested it with chalk :) Who knows? sodium persulphate is a powerful oxidizer which actually gives off oxygen readily, perhaps that oxygen is reacting with something in the soil. The smell would give a good indication of what it is......especially if theres sulphur in it.
 
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jbeng

Member
I've not used spent FeCl3 for that, but here you can get copper sulfate crystals (CuSO4) at the local hardware store. It's used for killing tree roots which have grown into your sewer system.

Jeff
 

Hero999

Banned
It looks like it'll probably work then.

I've read that sodium persulphate is used as a soil conditioner so it doesn't look like it'll do much harm; it's the copper I'm more worried about.
 

kchriste

New Member
Forum Supporter
One thing to consider is the fact that only the outer ring of the tree is actually alive and growing. I've heard that pealing the bark off the stump, into the ground as far as possible, is an effective way of killing it.
 

giftiger_wunsch

New Member
I've read that sodium persulphate is used as a soil conditioner so it doesn't look like it'll do much harm; it's the copper I'm more worried about.
Having heavy metals in the soil certainly isn't going to make it easy to grow anything there for a while... indeed, sodium persulphate shouldn't be a problem; neither sodium or sulphate ions are particularly toxic unless in high concentrations, so there shouldn't be a lasting effect on the soil, but heavy metal ions such as copper or iron are a different matter.

I am soo testing this on the mess of brambles at the back of my garden once I get some more etchant :D I left my bag of ferric chloride etchant granules on my window sill and the next time I checked the entire bag had turned into a big slop :mad: didn't even get chance to use any of them.
 
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giftiger_wunsch

New Member
As for the reacting with clay, there are a huge variety of different clays, and most are a complex mixture of various compounds, so without knowing the type of clay and the chemicals found in the clay, it's difficult to predict why it's reacting like that, especially if not with chalk.

Any idea what type of gas is being released? Does it smell like rotten eggs? It could be sulphur dioxide, since you're using sodium persulphate solution.
 

Hero999

Banned
Having heavy metals in the soil certainly isn't going to make it easy to grow anything there for a while... indeed, sodium persulphate shouldn't be a problem; neither sodium or sulphate ions are particularly toxic unless in high concentrations, so there shouldn't be a lasting effect on the soil, but heavy metal ions such as copper or iron are a different matter.
Copper isn't that toxic; it's not like lead, mercury or cadmium and as far as I'm aware it's not even classified as a heavy metal. Copper is one of those elements that essential for healthy plants and people in small traces, yet toxic in large doses. Providing I've not put too much copper into the soil, it should wash out in a few years and eventually be beneficial to the soil. I just hope I haven't added so much copper to the soil that it will kill the surrounding vegetation, leaving a bare spot where nothing will grow for years.

I am soo testing this on the mess of brambles at the back of my garden once I get some more etchant :D I left my bag of ferric chloride etchant granules on my window sill and the next time I checked the entire bag had turned into a big slop :mad: didn't even get chance to use any of them.
That's normal, it absorbs water.

I hope you haven't thrown it out, the chances are you can still use it. I'd recommend diluting the whole lot, even if it means making a saturated solution which you can dilute further to use.

We used to use ferric chloride at school, I've never used the stuff at home because it's too messy.
Any idea what type of gas is being released? Does it smell like rotten eggs? It could be sulphur dioxide, since you're using sodium persulphate solution.
No, it smells like bleach.

One thing to consider is the fact that only the outer ring of the tree is actually alive and growing. I've heard that pealing the bark off the stump, into the ground as far as possible, is an effective way of killing it.
I'll bear that in mind.

The trouble is laburnum is a very hard wood and the bark doesn't easily peal.

I thought that the brown wood in the middle is dead and the outer wood is still alive but on closer inspection, some of the brown intersects the rings so that doesn't make sense; I could be wrong though.
 

giftiger_wunsch

New Member
Copper isn't that toxic; it's not like lead, mercury or cadmium and as far as I'm aware it's not even classified as a heavy metal.
It is classified as a heavy metal, and is toxic. Same goes for iron. Hence the 'harmful' warning on copper sulphate. Copper is a heavy enough element to bind to and denature proteins, so it produces toxic heavy metal effects. For example copper sulphate is deemed harmful, and can have toxic effects in relatively small doses as it differentiates into copper ions and sulphate ions. Wikipedia suggests that the LD50 for copper sulphate is approximately 300mg/kg, i.e. that 300mg per kg of body weight is enough to kill 50% of test subjects. Compare that to cadmium sulphate with an approximate LD50 of 280mg/kg, or lead sulphate, which also has an LD50 of 300mg/kg. I believe the primary reason that lead is considered more dangerous that copper is that in a metallic state, lead will dissolve in water and produce ions much more readily than copper or most other metals. As for mercury, it's highly volatile.

Anyway, biochemistry rant over :D


Hero999 said:
That's normal, it absorbs water.
I expected that since it is quite important that they remain in dry granular form, measures would have been taken to remove as much of the moisture from inside the bag as possible. The bag was still sealed when it turned to a congealed slop.

I did throw out the ferric chloride; a big congealed slop seemed little use. I'm still getting into electronics so I would probably only need to use the etchant solution at far apart intervals, so even if I made the whole pack into a solution for later use, I believe the website suggests it'll only be good for a couple of days in that form. I'd probably only get one use out of it.

Hero999 said:
No, it smells like bleach.
I believe bleach smell is usually caused by chlorine or a chlorine compound; but since you're using sodium persulphate rather than ferric chloride, I don't know how you managed that. Ammonia smell is also often associated with bleach, but again I don't see any reason for the formation of ammonia.
 
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Dean Huster

Well-Known Member
I remember as a kid, helping Dad drag a gunny sack full of copper sulfate around the pond to get rid of the green "pond scum". Didn't seem to harm the fish, although who knew in 1964 (or cared) what effect it had on the fish or the groundwater? I just know that I had a ready source of copper sulfate and had great fun copper plating with the stuff.
 

giftiger_wunsch

New Member
I believe a low concentration copper sulphate solution can be used as an algaecide while not noticibly harming fish; it is possible that their gills reduce their bodies' exposure to the copper ions in solution, so it has a much more pronounced effect on algae than on fish at low concentrations.

Higher concentrations will kill the fish and anything else living in the water. Virtually all organisms are vulnerable to heavy metal toxicity due to their non-specific toxicity. They can cause the production of free radicals which can cause oxidative damage to virtually anything since they're extremely reactive.
 

Hero999

Banned
I believe the primary reason that lead is considered more dangerous that copper is that in a metallic state, lead will dissolve in water and produce ions much more readily than copper or most other metals. As for mercury, it's highly volatile.
I thought that lead and mercury are considered to be more dangerous than copper because they accumulate more and play no useful role within the human body.

It might also have something to do with copper being an essential trace element and lack of it can make one very ill.
Copper deficiency - Wikipedia, the free encyclopedia
 

giftiger_wunsch

New Member
I thought that lead and mercury are considered to be more dangerous than copper because they accumulate more
Something having no useful purpose doesn't necessarily make it more dangerous, but you do have a point about accumulation: I don't know how excess copper ions are dealt with in the body, but I have had lectures on how iron is recycled and excess iron is safely transported in the blood and excreted (you'll have to excuse the fact that I can't recall the details, I last studied it about 6 months ago. That's one more thing to revise in my summer break from uni ;))

As for lead, cadmium, and mercury, there probably aren't any specific biological methods by which they're excreted, so it's easier to reach the lethal dose. I believe most heavy metals are incorporated into keratins and are ultimately removed from the body when keratinised cells are shed. It's a slow process, which makes it easier for these elements to build up, than for iron and copper.


Anyway in solution, copper is still as toxic as most other heavy metals, just somewhat easier to excrete.


By the way, thanks for the interesting article on copper deficiency, though it appears wikipedia's somewhat lacking on the subject. It seems the role of copper in humans isn't fully understood, perhaps that's why I haven't yet learned the mechanisms by which it's removed :)

Anyway, sorry for devolving into biochemistry ;)
 
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jbeng

Member
I have some very persistent thistles I may have to experiment on...
I've found Ortho Brush-B-Gone to be quite effective on just about every kind of plant. Nice thing is that it is actually biodegradable, with a half life of 30-90 days.

Jeff
 

giftiger_wunsch

New Member
I've found Ortho Brush-B-Gone to be quite effective on just about every kind of plant. Nice thing is that it is actually biodegradable, with a half life of 30-90 days.

Jeff
Never heard of that, but I think the brambles in my garden are beyond hope. Every year or two I dig them all up, getting as many roots as possible. Every year they're back :mad: Weed killer isn't likely to ever completely remove them, either. It's really my parents' problem but the brambles bug me enough to want to be rid of them :D Dumping etchant on them is probably a bad idea though. Next time I dig them up I'll just grab the most resilient grass seeds I can find, and let the weeds try to compete with tough grass. :D
 
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Hero999

Banned
Anyway in solution, copper is still as toxic as most other heavy metals, just somewhat easier to excrete.
That makes sense, so long term exposure to low cadmium lead and mercury levels is more dangerous than copper, yet all are equally dangerous in acute doses.

Never heard of that, but I think the brambles in my garden are beyond hope. Every year or two I dig them all up, getting as many roots as possible. Every year they're back :mad: Weed killer isn't likely to ever completely remove them, either.
You only need a tiny little bit of root or stem for brambles to come back and even if you manage to remove all of the plant, the soil will be packed with seeds which can stay dormant for years like mines. :D
 

giftiger_wunsch

New Member
Hero999 said:
You only need a tiny little bit of root or stem for brambles to come back and even if you manage to remove all of the plant, the soil will be packed with seeds which can stay dormant for years like mines. :D
Rargh *shoots messenger* :mad: :D Still, if I level them back down to the ground an dig up as many roots as I can, and then put down a load of resilient grass seed, it should overwhelm any new weeds trying to grow back. And anything which does force itself through the grass will be swiftly slaughtered. :D
 

Hero999

Banned
I'd advise a lawn weed killer, it'll kill everything except plants from the grass genus.

EDIT:
It only kills the plant when it's sprayed onto the leaves though so you'll have to wait until it regrows a bit before you use it.
 
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