A sort of chemistry question

tringle

Not ground breaking science but just something I'm wondering about.

I have a vegetable garden and a huge amount of weeds on our driveway, patio and elsewhere. I don't want to use chemical weed killers and so use a combination of vinegar, salt and washing up liquid (5 litres vinegar, 1 cup salt and squirt washing up liquid). I used it and its works great. I used it out on the patio between the paving stones, they are large grey stones. Obviously when I sprayed you can see it is wet and then it dries in leaving a small mark which goes. However, this week it was very hot when I sprayed, it dried quickly but late in the evening when it got cool the "wet" marks reappeared and had spread. they where still there in the morning and once again disappeared during the day but came back in the cold evening again.

So, I'm just curious as to the scientific reason for this....any ideas?

locum-motion

tringle wrote: »

... I don't want to use chemical weed killers ...


...use a combination of vinegar, salt and washing up liquid (5 litres vinegar, 1 cup salt and squirt washing up liquid)...

Just what do you think "vinegar", "salt" and "washing up liquid" are, if they're not "chemical"?


EVERYTHING is "chemical". EV. ER. Y. THING. No exceptions.



For the record, the items you named are, in order:

Acetic Acid
Sodium Chloride
A mixture of many chemicals, but predominantly Dihydrogen Monoxide with some detergents in it too, such as Sodium Lauryl Sulphate.


Did you know the following about Dihydrogen Monoxide?

Dihydrogen monoxide:
is also known as hydroxyl acid, and is the major component of acid rain.
contributes to the "greenhouse effect".
may cause severe burns.
contributes to the erosion of our natural landscape.
accelerates corrosion and rusting of many metals.
may cause electrical failures and decreased effectiveness of automobile brakes.
has been found in excised tumors of terminal cancer patients.

Despite the danger, dihydrogen monoxide is often used:
as an industrial solvent and coolant.
in nuclear power plants.
in the production of styrofoam.
as a fire retardant.
in many forms of cruel animal research.
in the distribution of pesticides. Even after washing, produce remains contaminated by this chemical.
as an additive in certain "junk-foods" and other food products.

endacl

^^

endacl

locum-motion wrote: »

EVERYTHING is "chemical". EV. ER. Y. THING. No exceptions.

Oh yeah? What about a shadow?

locum-motion

A shadow isn't a thing!!

endacl

locum-motion wrote: »

A shadow isn't a thing!!

Pfffftt....

I'm looking at one now.

:rolleyes:

tringle

locum-motion wrote: »

Did you know the following about Dihydrogen Monoxide?

Dihydrogen monoxide:
is also known as hydroxyl acid, and is the major component of acid rain.
contributes to the "greenhouse effect".
may cause severe burns.
contributes to the erosion of our natural landscape.
accelerates corrosion and rusting of many metals.
may cause electrical failures and decreased effectiveness of automobile brakes.
has been found in excised tumors of terminal cancer patients.

Despite the danger, dihydrogen monoxide is often used:
as an industrial solvent and coolant.
in nuclear power plants.
in the production of styrofoam.
as a fire retardant.
in many forms of cruel animal research.
in the distribution of pesticides. Even after washing, produce remains contaminated by this chemical.
as an additive in certain "junk-foods" and other food products.

I wasn't asking for a lecture, I used a "squirt" of washing up liquid. The ingredients I used are perfectly safe to put on my chips or wash my dishes with so wont cause planet meltdown this week. However if you want to visit I'm happy to make you Monsanto Roundup soup...after all its still only a chemical.
I withdraw my question and will slink away back to forums more suitable for those of us less brainy.

Though I notice despite all the info you felt the need to offer, my question wasn't answered.

endacl

tringle wrote: »

I wasn't asking for a lecture, I used a "squirt" of washing up liquid. The ingredients I used are perfectly safe to put on my chips or wash my dishes with so wont cause planet meltdown this week.

http://www.theecologist.org/green_green_living/behind_the_label/268721/behind_the_label_fairy_liquid.html

tringle

and Ecover is the one I use.

KAGY

tringle wrote:

I don't want to use chemical weed killers and so use a combination of vinegar, salt and washing up liquid .... So, I'm just curious as to the scientific reason for this....any ideas?

No pedantic point scoring here :-)
my *guess* is the solution has dried into a very thin layer which is hygroscopic, when it gets cool at night and the water vapour in the air condenses and re-wets it.
When something is wet the surface is smoother and you don't get as much light scattering in all directions making the colour more saturated.

bduffy

KAGY wrote: »

No pedantic point scoring here :-)
my *guess* is the solution has dried into a very thin layer which is hygroscopic, when it gets cool at night and the water vapour in the air condenses and re-wets it.
When something is wet the surface is smoother and you don't get as much light scattering in all directions making the colour more saturated.

Just to add to this, I think the question the op asked was what kind of chemistry is going on. I think that the chemistry is over as the acid has reacted with a mineral (tile), leaving a porous surface which can soak up water and then dry out.

tringle

Thanks...that's the sort of things I was thinking. That the liquid evaporated quickly but the chemicals attracted water back in the cooler evening and held it....something like that. I was surprised it happened a second night as well, but it was two very hot days.
I'm always fascinated by "kitchen science".

locum-motion

tringle wrote: »

I wasn't asking for a lecture, I used a "squirt" of washing up liquid. The ingredients I used are perfectly safe to put on my chips or wash my dishes with so wont cause planet meltdown this week. However if you want to visit I'm happy to make you Monsanto Roundup soup...after all its still only a chemical.
I withdraw my question and will slink away back to forums more suitable for those of us less brainy.

Though I notice despite all the info you felt the need to offer, my question wasn't answered.

That whooshing sound over your head is your complete failure either to read or to understand what I wrote, or recognise that it was tongue in cheek.

In case it was failure to understand: Dihydrogen Monoxide is better known as 'water'!

bduffy

endacl wrote: »

http://www.theecologist.org/green_green_living/behind_the_label/268721/behind_the_label_fairy_liquid.html

I just read this and saw numerous spelling mistakes in the chemical names and then came across this "For a detergent to be considered biodegradable by the EU, it need only break down by 660 per cent within 28 days".

I'm not sure how something can break down by over 600 percent....I can understand increasing by 600% but not decreasing....it would appear that the author copied a lot of information (with no references) and makes blanket statements.

Anyhow, back to the day job.....