Using Caustic soda (NaOH) to free stuck seatpost



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Andy P wrote:
> "the Mark" <[email protected]> wrote
>
>> The warning about sulphuric and other strong acids is to do with the chance of it *spitting*, the
>> reaction is a lot more violent.
>
> At the risk of sounding pedantic (but hey it makes achange from chain lubricants and helmets!)
> there's nothing inherently dangerous about adding water to hydrochloric or nitric acid. It's just
> sulphuric that's a bit iffy.

Yes, so it is but keep a mixture of conc. hydrochloric and nitric acids away from metal. We used to
use it to dissolve solder for analysis where I worked over 20 years ago.
--
Mark

I'm getting something special built for me.
 
"Tim Woodall" <[email protected]> wrote

> There aren't many chemicals that can't splash when being diluted. But adding the acid/alkali to
> the water is standard practice. (Obviously when bringing a solution up to volume you need to top
> off with water at the end)
>
> <http://www.kent.ac.uk/physical-sciences/safety/chemicals.htm>
>
> Corrosive Chemicals The common ACIDS and ALKALIS (e.g. sulphuric acid, hydrochloric acid, nitric
> acid, sodium hydroxide, potassium hydroxide) cause most chemical burns so great care should always
> be taken when using them. When diluting, always add acid to water and not vice versa. If you are
> splashed with acid or alkali, wash immediately with large quantities of cold water.
>

Personally, I prefer to add water to a concentrated chemical (sulphuric acid excepted) rather than
vice versa because experience tells me the risk of the chemical running down the side of whatever
you're pouring it out of even if it's a laboratory beaker is higher than that of potential splashing
doing it the other way round.

I must say I was staggered at the list of chemicals & associated hazards on the website you
mentioned. Sulphuric acid, bromine or conc. hydrogen peroxide not corrosive? Acetone not highly
flammable? etc. Don't think you'd find any chemical suppliers to agree with that. And putting such
incorrect information on a public website is highly irresponsible. Haven't looked at the rest of it
yet. Sincerely hope you don't work there.
 
Andy P wrote:
> "Tim Woodall" <[email protected]> wrote
>
>
>> There aren't many chemicals that can't splash when being diluted. But adding the acid/alkali to
>> the water is standard practice. (Obviously when bringing a solution up to volume you need to top
>> off with water at the end)
>>
>> <http://www.kent.ac.uk/physical-sciences/safety/chemicals.htm>
>>
>> Corrosive Chemicals The common ACIDS and ALKALIS (e.g. sulphuric acid, hydrochloric acid, nitric
>> acid, sodium hydroxide, potassium hydroxide) cause most chemical burns so great care should
>> always be taken when using them. When diluting, always add acid to water and not vice versa. If
>> you are splashed with acid or alkali, wash immediately with large quantities of cold water.
>>
>
>
> Personally, I prefer to add water to a concentrated chemical (sulphuric acid excepted) rather
> than vice versa because experience tells me the risk of the chemical running down the side of
> whatever you're pouring it out of even if it's a laboratory beaker is higher than that of
> potential splashing doing it the other way round.
>
> I must say I was staggered at the list of chemicals & associated hazards on the website you
> mentioned. Sulphuric acid, bromine or conc. hydrogen peroxide not corrosive? Acetone not highly
> flammable? etc. Don't think you'd find any chemical suppliers to agree with that. And putting
> such incorrect information on a public website is highly irresponsible. Haven't looked at the
> rest of it yet. Sincerely hope you don't work there.
>
>
>
>
>
Perhaps if you had examined the rest of the page you might have noticed some of the other
information about hazardous chemicals. For example, the table of low flashpoint chemicals includes
includes acetone, with appropriate cautions. The first list of hazardous chemicals lists the
primary hazards that one might encounter in the laboratory which are associated with the listed
chemicals, not all of them. Those hazards are the ones associated with personal injury, not lab
destruction. And, in truth, vapor inhalation is usually what one would worry about with respect to
quantities of acetone.

We do not usually describe the actions of strong acids and the like as corrosive when applied to
human skin, irritant is the term used. Corrosion is a term usually applied to metals.

Back to the original topic of this exchange of views, the reason we add acid to water is because of
the large, exothermic heat of solution for these chemicals. When you add acid to water the acid
molecules are immediately solvated and a large amount of heat is liberated. This can cause
spattering; fortunately if you have added acid to water most of what is spattered is water or
dilute acid.

Should you, on the other hand, add some water to Con Sulphuric acid, the heat liberated as the water
solvates the H2SO4 causes it to get hot very quickly, turning it to steam (so to speak- worst case)
and spatters the Con Sulphuric around.

For this reason I used to teach my students (and now tell my techs) "Acid to Water". Vis a vis your
concerns about pouring, try using a glass rod to pour acids. You will find that it eliminates
dribbling.

Bill
 
"Dr. William H. Pence" <[email protected]> wrote

> Perhaps if you had examined the rest of the page you might have noticed some of the other
> information about hazardous chemicals. For example, the table of low flashpoint chemicals includes
> includes acetone, with appropriate cautions. The first list of hazardous chemicals lists the
> primary hazards that one might encounter in the laboratory which are associated with the listed
> chemicals, not all of them. Those hazards are the ones associated with personal injury, not lab
> destruction. And, in truth, vapor inhalation is usually what one would worry about with respect to
> quantities of acetone.

Right, so inhaling a bit of acetone in an open laboratory is more of a hazard than inadvertantly
setting yourself on fire because nobody told you it was flammable. I did flick through the rest of
the website and you don't need to know anything about chemicals to appreciate that giving
inconsistent and confusing information is very bad practice.

> We do not usually describe the actions of strong acids and the like as corrosive when applied to
> human skin, irritant is the term used. Corrosion is a term usually applied to metals.

"We" as in who? Certainly not anyone with any knowledge of the legislation affecting the packaging
or use of chemicals. Telling people something is irritant when in fact it will cause severe burning
is negligent in the extreme.

> Back to the original topic of this exchange of views, the reason we add acid to water is because
> of the large, exothermic heat of solution for these chemicals. When you add acid to water the acid
> molecules are immediately solvated and a large amount of heat is liberated. This can cause
> spattering; fortunately if you have added acid to water most of what is spattered is water or
> dilute acid.

"Solvated"? is that a proper word?

> Should you, on the other hand, add some water to Con Sulphuric acid, the heat liberated as the
> water solvates the H2SO4 causes it to get hot very quickly, turning it to steam (so to speak-
> worst case) and spatters the Con Sulphuric around.

Yes, but still just sulphuric and not every concentrated chemical or even every concentrated acid
which was my original point.

> For this reason I used to teach my students (and now tell my techs) "Acid to Water". Vis a vis
> your concerns about pouring, try using a glass rod to pour acids. You will find that it eliminates
> dribbling.

I did try the glass rod tip once but it didn't work for me. Obviously needs practice. I'm sure more
people have experienced spilling milk when pouring it into a cup of coffee than the coffee splashing
out. Couldn't decide whether or not you were just trolling but my girlfriend's away and there's not
much on telly. Anyhow if you are really in the position of teaching people chemistry please go and
learn some basic health & safety issues.
 
"the Mark" <[email protected]> wrote

> Yes, so it is but keep a mixture of conc. hydrochloric and nitric acids
away
> from metal. We used to use it to dissolve solder for analysis where I
worked
> over 20 years ago.

Out of interest does that give off hydrogen as in hydrochloric or nitrogen dioxide as in
nitric. Or both.
 
Andy P wrote:
> "the Mark" <[email protected]> wrote
>
>> Yes, so it is but keep a mixture of conc. hydrochloric and nitric acids away from metal. We used
>> to use it to dissolve solder for analysis where I worked over 20 years ago.
>
> Out of interest does that give off hydrogen as in hydrochloric or nitrogen dioxide as in nitric.
> Or both.

I think it will give off hydrogen no matter what though. I should know for sure but I've forgotten
all the chemistry I don't need and all the reference books are at work.
--
Mark

I'm getting something special built for me.
 
Andy P wrote:
> "Dr. William H. Pence" <[email protected]> wrote
>
>
>>Perhaps if you had examined the rest of the page you might have noticed some of the other
>>information about hazardous chemicals. For example, the table of low flashpoint chemicals includes
>>includes acetone, with appropriate cautions. The first list of hazardous chemicals lists the
>>primary hazards that one might encounter in the laboratory which are associated with the listed
>>chemicals, not all of them. Those hazards are the ones associated with personal injury, not lab
>>destruction. And, in truth, vapor inhalation is usually what one would worry about with respect to
>>quantities of acetone.
>
>
> Right, so inhaling a bit of acetone in an open laboratory is more of a hazard than inadvertantly
> setting yourself on fire because nobody told you it was flammable.

Actually, yes. Bulk quantities of flammable solvents are stored in fireproof cans with mesh fire
damp screens and smaller quantities are stored in glass or plastic containers with FLAMMABLE labels
on them. When I was taking sophomore organic chemistry we still used Bunsen burners (that was 35
years ago-surely they are using heating mantles now) we were certainly aware of what was flammable
and what was not, and we were extremely careful. I suspect that open flames are not common anymore.

But you are begging the question; the web page clearly highlighted the hazard of the low flash
point of acetone, as well as other chemicals which shared that hazard. The fact that they listed
the personal effects of the chemical in one place and the physical hazards in another does not
render them

I did flick through the rest of the website and you don't
> need to know anything about chemicals to appreciate that giving inconsistent and confusing
> information is very bad practice.

Could you cite some specific instances of confusing information?

>
>
>>We do not usually describe the actions of strong acids and the like as corrosive when applied to
>>human skin, irritant is the term used. Corrosion is a term usually applied to metals.
>
>
> "We" as in who? Certainly not anyone with any knowledge of the legislation affecting the packaging
> or use of chemicals. Telling people something is irritant when in fact it will cause severe
> burning is negligent in the extreme.

You think so? I don't agree. A solution of 0.01 M HCl is not likely to burn you very badly. A
solution of 3 M would cause much more irritation. You add vinegar to your salad but glacial acetic
acid is quite a bit stronger. You use hydrogen peroxide to cleanse wounds but we also use it as an
oxidiser for our chemical lasers.

Detailed information on hazardous chemicals is available in the Material Safety Data Sheets, which
should be readily available in any laboratory. There you will probably find the detailed information
you seem to desire.

>
>
>>Back to the original topic of this exchange of views, the reason we add acid to water is because
>>of the large, exothermic heat of solution for these chemicals. When you add acid to water the acid
>>molecules are immediately solvated and a large amount of heat is liberated. This can cause
>>spattering; fortunately if you have added acid to water most of what is spattered is water or
>>dilute acid.
>
>
> "Solvated"? is that a proper word?

Actually, yes. A solvent will solvate, or produce a sphere (so to speak) of solvation
around a solute.

>
>
>>Should you, on the other hand, add some water to Con Sulphuric acid, the heat liberated as the
>>water solvates the H2SO4 causes it to get hot very quickly, turning it to steam (so to speak-
>>worst case) and spatters the Con Sulphuric around.
>
>
> Yes, but still just sulphuric and not every concentrated chemical or even every concentrated acid
> which was my original point.

Your original point is incorrect. If you look at the CRC handbook of Chemistry and Physics, you will
find a table of Heats of Solution for various substances. Strong acids have large exothermic
reactions upon contact with water; some strong bases share this characteristic, others do not.
Crystalline NaOH is strongly exothermic. The steam explosion when a water molecule jumps on the
loosely held proton of a strong acid is something to see.

>
>
>>For this reason I used to teach my students (and now tell my techs) "Acid to Water". Vis a vis
>>your concerns about pouring, try using a glass rod to pour acids. You will find that it eliminates
>>dribbling.
>
>
> I did try the glass rod tip once but it didn't work for me. Obviously needs practice. I'm sure
> more people have experienced spilling milk when pouring it into a cup of coffee than the coffee
> splashing out. Couldn't decide whether or not you were just trolling but my girlfriend's away and
> there's not much on telly. Anyhow if you are really in the position of teaching people chemistry
> please go and learn some basic health & safety issues.

Actually I don't teach people chemistry anymore, I'm president of an electro-optics firm. Perhaps
you could enlighten me as to your wealth of experience in this area? I'm always looking to enhance
my laboratory safety program. Perhaps my Safety Officer could contact you as to proper handling and
storage of hazardous chemicals?

I begin to understand Mr. Brandt's frustration.

Oh, and regarding the original poster's questions, I have found that cutting out the seatpost with a
hacksaw blade held in a fixture to work well, though it is painfully slow.
 
In article <[email protected]>, [email protected] (Justin
Brookman) wrote:

> Hi all
>
> I've read with interest the posts concerning freeing a stuck aluminmium seatpost with caustic
> soda, and have had a go at it yesterday. It was a bit hairy and their was no doubt that a chemical
> reaction did occur. (bubbling and foaming)

My father used to soak seized engine parts (from boat outboard motors whose owners had accidentally
dunked them in salt water) in cola overnight. Worked a treat.
 
"Dr. William H. Pence" <[email protected]> wrote

> Your original point is incorrect. If you look at the CRC handbook of Chemistry and Physics, you
> will find a table of Heats of Solution for various substances. Strong acids have large exothermic
> reactions upon contact with water; some strong bases share this characteristic, others do not.
> Crystalline NaOH is strongly exothermic. The steam explosion when a water molecule jumps on the
> loosely held proton of a strong acid is something to see.
>
> Actually I don't teach people chemistry anymore, I'm president of an electro-optics firm. Perhaps
> you could enlighten me as to your wealth of experience in this area? I'm always looking to enhance
> my laboratory safety program. Perhaps my Safety Officer could contact you as to proper handling
> and storage of hazardous chemicals?

I don't think you can possibly really believe what you're trying to argue here so I'll ignore most
of it if that's ok. But I did do a bit of research in the course of my job this morning. I regularly
make up solutions of differing strengths from concentrated supply stocks so I noted a few
observations.

Adding 1 vol water to 1 vol conc. HCl (yes water to acid) raises the temp. to 32 degrees. Adding 1
vol water to 1 vol conc. HNO3 raises the temp. to 42 degrees. No spitting, splashing etc.
Conclusion, safe thing to do.

Adding 1 vol conc. H2SO4 to 1 vol water (acid to water this time) raises the temp. to 108 degrees.
(The resulting solution isn't boiling at this temp.) Conclusion, a far more vigorous reaction and
not something I'd do the other way round by adding water to the acid.

Adding water to NaOH pellets to make a 15M solution raises the temp to 88 degrees. No spitting,
splashing etc. but easy to see that adding a smaller amount of water might result in boiling. Once
this concentrated solution had cooled adding more water didn't produce any appreciable temp. rise.
Conclusion safe thing to do.

A small piece of Al foil in this solution dissolved completely in about a minute but a 5mm thick
piece showed very little visible decrease in volume after fizzing away for 30 minutes.

Also in the interests of scientific health & safety research and complete stupidity I put some 15M
NaOH on my hand. It surprised me to find I didn't feel any effects until after 50 seconds and could
quite happily leave it for 2 minutes with no real burning. Conc sulphuric acid (18M) on the other
hand started to burn after 20 seconds and left a visible mark after washing off. Don't try it at
home kiddies.
 
On Thu, 19 Jun 2003 19:07:34 +0100, "Andy P" <[email protected]> wrote:

>A small piece of Al foil in this solution dissolved completely in about a minute but a 5mm thick
>piece showed very little visible decrease in volume after fizzing away for 30 minutes.

Al foil is 30 microns or so thick generally, IIRC. So using this solution on an Al bike frame for a
fairly extended period could certainly dissolve a fair bit of metal. If the stuff pools in places,
possibly enough to create a stress riser. It's definitely not a procedure for the fainthearted.

>Also in the interests of scientific health & safety research and complete stupidity I put some 15M
>NaOH on my hand. It surprised me to find I didn't feel any effects until after 50 seconds and could
>quite happily leave it for 2 minutes with no real burning. Conc sulphuric acid (18M) on the other
>hand started to burn after 20 seconds and left a visible mark after washing off. Don't try it at
>home kiddies.

And you have the unmitigated gall to call other people on safety issues?

Jasper
 
"Jasper Janssen" <[email protected]> wrote
"Andy P" <[email protected]> wrote:

> >Also in the interests of scientific health & safety research and complete stupidity I put some
> >15M NaOH on my hand. It surprised me to find I
didn't
> >feel any effects until after 50 seconds and could quite happily leave it
for
> >2 minutes with no real burning. Conc sulphuric acid (18M) on the other
hand
> >started to burn after 20 seconds and left a visible mark after washing
off.
> >Don't try it at home kiddies.
>
> And you have the unmitigated gall to call other people on safety issues?
>
> Jasper

Yes well what I do to myself is up to me. I've read the safety stuff and fully appreciated the
dangers of what I was doing. (ie no danger of doing myself any lasting damage so long as I'm
standing next to a bowl of water and a tap). But some people in this thread have been saying or
referring to things which could lead people other than themselves to underestimate the dangers of
using various chemicals and that's not a good thing to do. Eg. by saying H2SO4 is only irritant.
Ofcourse it might be only irritant at sufficient dilution (less than 1.5M if my memory's correct)
but unless you state the concentration you should class it as corrosive.
 
On Fri, 20 Jun 2003 17:01:53 +0100, "Andy P" <[email protected]> wrote:

>by saying H2SO4 is only irritant. Ofcourse it might be only irritant at sufficient dilution (less
>than 1.5M if my memory's correct) but unless you state the concentration you should class it as
>corrosive.

There's really no point in calling it corrosive, because corrosive is not a danger to humans. Humans
don't corrode, you see, not being made of metal. You're the one saying stupid **** leading to
underestimating of dangers, there.

Jasper
 
"Jasper Janssen" <[email protected]> wrote

> There's really no point in calling it corrosive, because corrosive is not a danger to humans.
> Humans don't corrode, you see, not being made of metal. You're the one saying stupid **** leading
> to underestimating of dangers, there.

I suddenly had the thought that perhaps I was missing somethingand the chemical hazard
classification system is different in the US to here in the Uk for some bizarre reason but
apparently not. For anyone interested (obviously not yourself).

http://www.howe.k12.ok.us/~jimaskew/msds/msdsinfo.htm

Scroll down to the glossary of MSDS terms section.
 
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