Problem with nitric acid etching fine silver

Jewelry Discussion
41

As for sodium bisulfate it is not listed as a carcinogen by the
IARC or any other regulatory agency that is listed in MSDS’s for
it, so I think your reasoning is lacking in a factual basis here.

I said so myself that there is no factual basis, I explained why
and I said that using deductive reasoning, you cannot come up with
any valid argumentation explaining that long term exposure to
aerosols of sodium bisulphate is not carcinogenic.

Deductive reasoning can also lead to the idea that the moon is made
of green cheese. Tests and facts are what is needed when talking
about hazerdous substances not deductive reasoning as the real world
is as often as not counter intuitive.

I do not agree with what Jim Binnion is saying about sulphuric
acid. Where do you get the idea that it is necessary for the acid
to reach boiling point to become a mist?

A liquids boiling point or more precisely its vapor pressure has
everything to do with its ability to evaporate. A substances
equilibrium vapor pressure often just called its vapor pressure is
the measurement of at what pressure and temperature a substance
transforms from liquid or solid to a gas. The boiling point is
actually the measurement of the vapor pressure when the pressure is
at ambient atmospheric pressure. So a liquid that has a high boiling
point has a low ability to evaporate. H2SO4 has a very low vapor
pressure when compared to say water.

Evaporation from a non boiling surface is fairly difficult to
calculate as there are many interactive variables but it is safe to
say that liquids with low vapor pressures like sulfuric acid are
very slow to evaporate. In the case of concentrated sulfuric acid I
have seen that for health and safety regulatory compliance measures
the evaporation rate is considered to be nil.

In the case of a pickle mixture of sulfuric acid and water at room
temperature the evaporation of the acid will be insignificant. The
vast majority of what evaporates from the mixture is water. A 10%
sulfuric acid pickle is strong enough that it doesn’t need to be
heated to work so the evaporation rate is very low. So your exposure
in this case is extremely low, not zero but assuming you have
anywhere near adequate ventilation there is little chance of inhaling
any sulfuric acid vapor.

Any aerosol is a mist.

Yes so as long as you don’t do anything to create an aerosol there
is no problem, that means no spraying of the acid solution and not
quenching hot metal into it.

Long term occupational exposure to sulphuric acid mist is
carcinogenic. There is no reason to think that the same exposure
to mist of sodium bisulphate is not carcinogenic. The fact that it
has not been tested does not prove that it is not carcinogenic.

Sodium bisulfate is a very commonly used industrial chemical, it is
highly unlikely that if it had a carcinogenic effect that it would
not have been noted and tested by now.

Given the similarities between sodium bisulphate and sulphuric acid
- they are identical except for one Na atom instead of one O atom
and it has one H atom less than H2SO4 -

By that kind of deductive logic you might feel perfectly safe to
drink hydrogen peroxide (H2O2) as it only has one extra oxygen atom.

James Binnion
James Binnion Metal Arts

42 
By that kind of deductive logic you might feel perfectly safe to
drink hydrogen peroxide (H2O2) as it only has one extra oxygen
atom.

Dihydrogen monoxide. Explosive mix of very flamable Hydrogen and
reactive oxygen. Chemical combinations are very different than their
components. Although H2O kills many.

jeffD
Demand Designs
Analog/Digital Modelling & Goldsmithing
http://www.gmavt.net/~jdemand

43 
Once the solution is boiling, put it outside, keep away from it and
let it cool.

Ummm, maybe a stupid question but, how do you carry the boiling acid
and keep away from it at the same time? Can you guarantee to someone
following this advice that they won’t slip?

You are very lucky you did not end up with a face full of acid.
Never, never, never add water to acid…

Hi Jim, Yes, I know, but I did this hundreds of times already.

I’m certainly not a chemist nor an odds maker but there are some
common sense issues in this thread that kinda scare me. But then I’m
the kind who doesn’t like to tempt fate beyond valid reason, I like
my eyeballs, mean to keep them. An odd quirk, I know.

44 
Please. This belongs to the same category of denial of which Peter
Rowe gave a brilliant example the other day: sulphuric acid may
cause severe burns, it may ignite the wood of a table, it may even
kill a couple of cells, but damaging DNA and causing mutation,
well no.

Alicia, I am not aware of giving any examples of brilliant denial.
In the above example, I’d point out that for a material to be
carcinogenic, it has to cause cellular damage capable of leading to a
mutation, but do so without killing the cell. If a material kills the
cell, there’s nothing left to mutate. In the case of sulphuric acid
mists over chronic exposure, the likely mechanism is a low level of
burn, causing scarring of some sort. Sodium bisulphate, while
similar to sulphuric acid in it’s ability to react with metallic
oxides, is NOT sulphuric acid in it’s reaction to organic proteins.
It’s much weaker. And, as others have noted as well as I, it doesn’t
form the same acid vapors. Yes, you might be able, if your sense of
smell is good enough, to detect a slight odor from your pickle pot.
But the human nose can detect concentrations of some chemicals at
levels so low as to be almost inconsequential in chemical terms.
That’s it’s function. To equate this with being able to cause cancer
is simply not a valid conclusion, and demonstrates an incomplete
understanding of why some chemicals at extremely low concentrations
can be carcinogenic, while others even at significant exposures,
might not be. You also suggest that just because the MSDS sheets
don’t list carcinogenic properties for sodium bisulphate doesn’t
mean it isn’t, is also not a valid deduction when you then suggest
that it must be because the two are similar. Sodium bisulphate is a
very widely used chemical, including in some cases, as a food
additive. You can bet that if there were any suggestion that it might
be carcinogenic, even an unproven possibility, the MSDS sheets would
suggest the possibility just to cover their butts. Yes, it has some
dangers, but it really isn’t the same as sulphuric acid.

And then on to the rest of your post. Well, frankly, I’m at a loss
just where to begin. Lets start with a question. Just how much formal
education do you have in chemistry? Have you ever taken a college
level chemistry class (or even a high school level one?) No, I’m
really not trying to insult you or anything. I’m just puzzled as
where you got these notions of how chemistry works. The deductions
you draw regarding chemical similarity of things based on whether
they have one more or less of a certain atom, or the like, is just
plain wrong. Chemistry just doesn’t work that way. Salts of any
reactive material are quite different in their effects than the
original acid or base. Just the difference of one sodium atom is
indeed a very big difference. So is the addition or deletion of one
oxygen atom, or even an electron or two. Take chlorine gas, for
example. Highly toxic, noxious, very reactive nasty stuff. Add one
sodium atom. Pretty inert table salt. Or start with sodium metal.
Almost explosively reactive stuff. Dangerous as hell. Add some
equally dangerous chlorine, and it’s almost neutral. Sodium is a
metal. Add it to sulphuric acid, and you get something quite
different from the original acid. Take one simple oxygen molecule. We
need the stuff to live, right? Add a carbon. simple innocuous black
stuff. The resulting gas is most definitely not something you want
to breath instead of oxygen. Very different from either the oxygen or
the carbon. Add a carbon atom to a nitrogen atom. Both materials are
pretty innocuous to begin with, but the combination is a cyanide ion.
bond it with hydrogen, and breath it in, and you’re dead really fast.
Bond it instead with iron, and it’s not very toxic at all. And either
one, even the very dangerous one, if at levels not lethal, are
handily removed by the liver, without carcinogenic risks (though
chronic low level cyanide exposure does have other risks) Or take
the insulin I need to take every day to live. Even without changing
the formula, if you just move the position of a few atoms around on
the molecule, it no longer works, or works radically differently.

As Jim so eloquently put it, deductive reasoning can lead you to
think the moon is green cheese. Logic is a wonderful thing, But it
can also be a trap if you’re not very careful with the starting
assumptions. basing a statement of “truth” just on appearances or
deductive reasoning is a really great way to get things very very
wrong.

While caution regarding potential dangers is always a wise choice to
make, and you are well advised to avoid things you think may be
dangerous or which you don’t fully understand, you should also be
cautious not to try and justify your caution with assumptions and
deductions that might not hold up. If you don’t trust or like sodium
bisulphate pickle, despite the assurances of others that it’s
reasonably safe, then simply don’t use it. No problem. Not liking it
is enough of a reason to not use it if you wish.

Peter

45

It may have been noted, but, if so, I missed it. Vapor and mist are
not the same. Normally one considers vapors to be oomposed of
materialsl which have evaporated from the fluid in question. Thus,
the materials are molecular in nature. The amount of any substance
in the vapor will depend upon the relative vapor pressures of the
materials in the fluid mix (and such factors as temperature, etc.).
Mists represent a “bulk” form composed of much larger amounts of the
liquid material in tiny droplets mechanically generated from the
liquid (splashes, sonication, sprays).

At room temperature, the vapor pressure of H2SO4 is low enough that
with dilute solutions there is minimal pulmonary danger (not zero,
but not large). Long exposue to either vapor or mist at high
concentration is very harmful as each of you knows. I keep H2SO4
solutions covered when not inactive use both in my laboratory and in
my studio. Concentrated and hot acids are used in the fume hood.

I know these comments are paddling in waters already stirred, but
stating things another way often helps.

GV

46

I see that everyone is doing its best to misunderstand me as much as
possible.

Thank you for proving my point about psychological resistance.

When I was working in Germany the head of the department’s favourite
proverb was ‘Those who think that they know everything are simple
misinformed’.

Deductive reasoning can also lead to the idea that the moon is
made of green cheese. Tests and facts are what is needed when
talking about hazerdous substances not deductive reasoning as the
real world is as often as not counter intuitive.

How would deductive reasoning lead to such an idea? Is there
anything pointing in that direction? Sorry, but can we keep this a
little bit serious?

I am all for tests and facts too, but I am not naive about them.
Tests do not teach you anything without an underlying theory and
hypotheses to reject or accept. But often tests are not possible,
which is the case here. How are you going to test sodium bisulphate
for health hazards? Put some dogs in a room and make them breathe
the stuff night and day? For how many years are you going to do
that? Till they die? You can give them a strong concentration, but
then you want to know the effects of long exposure to a low
concentration. It just isn’t practically feasible. As for facts, I
could give youa really long explanation on what constitutes facts
and how they are born - factsdo not exist in natureby themselves.

A liquids boiling point or more precisely its vapor pressure has
everything to do with its ability to evaporate.

This misses the point about what I said that it is not necessary to
consider boiling sulphuric acid. You ignore what I said earlier and
what are you actually implying isthat the experts who studied all of
this and concluded that workers having a greater chance of getting
cancer of the larynx are just plain wrong. Of course, you are not
going so far to actually state this, but that is your implication as
it is not possible that you and the scientistsare both right.
According to you, people living close to waste sites containing
sulphuric acid are not at greater risk for pulmonary disease either
because I guess that it is hard to find waste sites which
containboiling sulphuric acid. Sorry, but this is just plainwrong
and I find it sad that you do this.

Saying they are identical except for one Na atom instead of one O
atom and it has one H atom less than H2SO4" betrays a complete
lack of understanding of it all, I'm afraid.

Yes, this is complete lack of understanding Why, am I wrong?

The main difference between sodium bisulphate andsulphuric acid is
that sodium bisulphate hasa Na atom instead of a H atom. Since these
elements are very closely related, the differencein the two
compounds under considerationis supposed to bevery small, which
indeed it is, as you can learn in lower middle school.

A polishing machine is 1000 times more dangerous than your pickle
pot.

Good point. Let your pickle pot steam. Get compounds from your
polishing machine into your lungs. A bit of enamel perhaps here and
there. I am sure there is no cumulative effect.

Did you ever hear about acid rain? What do you think it is? It’s
sulphuric acid - SO2 becoming SO3 and finally H2SO4 - which
attaches itself to small particles in the air.

That's not the process of acid rain damage!

That is exactly what acid rain is - look it up in any textbook.

I didn’t especially expect a thank you from this community to bring
this to your attention, but I would have appreciated it if some
people would have acknowledged by now that they are wrong. There’s no
shame in being wrong - after all, no one knows everything. But I do
not think that producing crooked arguments speaks in anyone’s favour.

47 
It may have been noted, but, if so, I missed it. Vapor and mist
are not the same. Normally one considers vapors to be oomposed of
materialsl which have evaporated from the fluid in question. Thus,
the materials are molecular in nature. The amount of any substance
in the vapor will depend upon the relative vapor pressures of the
materials in the fluid mix (and such factors as temperature,
etc.). Mists represent a "bulk" form composed of much larger
amounts of the liquid material in tiny droplets mechanically
generated from the liquid (splashes, sonication, sprays).

Exactly, although mists may also be formed by vapors condensing back
to liquid form from vapor if the temperature or pressure shifts to
the favor the phase change. In any case to H2SO4 mists you are going
to have to do something beyond having a pickle pot at or slightly
above ambient temperature and ambient pressure. Typically the only
way a smith would generate sulfuric acid mist is by quenching hot
metal in the pickle.

At room temperature, the vapor pressure of H2SO4 is low enough
that with dilute solutions there is minimal pulmonary danger (not
zero, but not large). Long exposue to either vapor or mist at high
concentration is very harmful as each of you knows. I keep H2SO4
solutions covered when not inactive use both in my laboratory and
in my studio. Concentrated and hot acids are used in the fume hood.

Right on all counts.

James Binnion
James Binnion Metal Arts

48 
The main difference between sodium bisulphate andsulphuric acid is
that sodium bisulphate hasa Na atom instead of a H atom. Since
these elements are very closely related, the differencein the two
compounds under considerationis supposed to bevery small, which
indeed it is, as you can learn in lower middle school.

Wow. Sodium and hydrogen are very closely related?

Excess hydrogen ions are what make a compound acidic. Replacing a
hydrogen atom with a sodium atom has an enormous effect on it’s
acidity, corrosiveness, and the like Both sodium and hydrogen are
both classified as metals and are both very reactive materials, but
they are a lot more different in behavior even as elements than are
many elements near to each other on the periodic table, and they
certainly are not similar in the effect they have on compounds they
are part of, nor do they even have similar levels of chemical
reactivity. Hydrogen, for example, is easily bonded with carbon and
oxygen to make a wide array of hydrocarbon and other organic
molecules. Sodium and Carbon? Well, add oxygen and you can get sodium
carbonate, but that’s not even close. Sodium Chloride is table salt.
Hydrogen Chloride? That’s hydrochloric acid. Don’t sprinkle it on
your veggies.

Substituting a supposedly similar element for another in a compound
does not automatically mean the two compounds would be similar. Even
the assumption that it might be is unlikely to be true very often. If
you learned this in middle school, then I suggest you graduate to a
high school level chemistry course. And how are you determining that
two elements are similar? Their position on the periodic table would
be the usual means to make that assumption, but it just doesn’t work
that way. And while hydrogen and sodium are both on the left column
of the table, they aren’t even adjacent. Yes, a similar position on
the table can sometimes indicate similar chemistries or behaviors.
Chlorine and Fluorine for example, can have compounds that do have
distinct similarities. But oxygen and sulphur? Nitrogen and
phosphorus or arsenic?

Perhaps the key here is that while different closely related
elements may have similarities in their chemical behavior, electron
shells or bonds, etc, that’s very different from saying they have
similar behaviors in relationship to human health risks. And of all
the closely related pairs of elements you might have picked that are
two spots apart vertically, I’d have to say Hydrogen versus just
about anything else, is among the least alike.

Substituting a sodium atom for a hydrogen one is indeed a large and
important change, despite what you may have learned in middle school.

Again, I’d suggest that if you are not comfortable with using sodium
bisulphate pickle, then simply don’t do so, though your use instead
of actual sulphuric acid seems bizarre, as it’s the much more
dangerous of the two. But in any case, you need no other reason not
to use a given chemical than to state that you are not comfortable
with it. Just please try to avoid defending this choice with
chemistry lessons that the rest of us cannot resist taking aim at.
It’s too easy a target, I’m afraid. Makes us look catty and nasty,
and makes you look like you don’t know what you’re talking about. I’d
guess both are not really true for the most part. Just stick with the
knowledge you really have mastered, or for which you can provide
reliable independent references (such as, in this case, MSDS sheets
that DID mention a risk), OK? And I’ll back out of this silly
debate. Enuff mud slung about already, and I no doubt did my share of
it. Sorry 'bout that.

Peter Rowe

49 
Ummm, maybe a stupid question but, how do you carry the boiling
acid and keep away from it at the same time? Can you guarantee to
someone following this advice that they won't slip?

I did not propose that anyone follows my example, I did not give any
advice. I just said that I do this. By all means, if you try this and
slip, make sure the acid hits the wall and not yourself. If you do
not feel like doing this, then don’t.

Peter, It is you who said that sulphuric acid is not carcinogenic.
Exposure to mists of sulphuric acids are carcinogenic, period, no
discussion, it has been recognised as such. Now you are going to
talk about everything, except this:

In the case of sulphuric acid mists over chronic exposure, the
likely mechanism is a low level of burn, causing scarring of some
sort.

If I may ask, do you think you are doing anyone a service with
statements like this? So far about the denial.

What I said is this: since long term exposure to mists of sulphuric
acid are carcinogenic (and this by far not the only problem that
sulphuric acid poses) and since sodium bisulphate is chemically
speaking very close to sulphuric acid, one should base one?s actions
on the precautionary principle and act as if occupational exposure
to sodium bisulphate is as dangerous as sulphuric acid itself. It
would not surprise me one bit if it would be carcinogenic also,
indeed, it makes complete sense to think so.

Lets start with a question. Just how much formal education do you
have in chemistry? Have you ever taken a college level chemistry
class (or even a high school level one?) No, I'm really not trying
to insult you or anything.

I am 50 years old and I have a PhD in physics. I have been doing
research at universities for most of my life. I got tired of working
in other countries and my husband didn’t like it where we were so we
came back to Ireland. I am setting up a studio as a goldsmith at the
moment. I can do professional work in goldsmithing. Now, let me ask
you in turn, what are your credentials in talking about chemistry?

Let me explain why sodium bisulphate and sulphuric acid are so
similar in their properties. You give examples about how much
difference one atom, one ion or even twisting (molecular handness)
in the case of insulin can make. In this case, the difference is
between one H atom and one Na atom. You give the example of Na and
Cl, which are both dangerous, making innocent table salt together.
Yes, but Na and Cl do not belong to the same group in the periodic
table. Na is an alkali metal (group 1), Cl is a halogen (group 17). C
and N, although their atomic number is close, belong to different
groups and therefore cannot be substituted for each other without
radical alternations. H and Na on the other hand do belong to the
same group. Not only that, H and He are the only period 1 elements
and the only element between H and Na in group 1 is Li. This means
that if you strip one H atom away and substitute a Na atom for it,
the compound you end up with will be chemically very similar to the
compound you started with. Furthermore, the combined atomic weight of
both compounds are resp. 50 and 48, which is very close. Same group,
similar qualities, per definition of group.

You also suggest that just because the MSDS sheets don't list
carcinogenic properties for sodium bisulphate doesn't mean it
isn't, is also not a valid deduction when you then suggest that it
must be because the two are similar. Sodium bisulphate is a very
widely used chemical, including in some cases, as a food additive.

One of the main uses of sulphuric acid is getting moist out of food.

You can turn this around as much as you want if you enjoy doing
this. The fact that an MSDS does not list this or that property does
not mean that this property is lacking. It depends on whether the
research has been done or not and in this case the research is
lacking, as so often.

As Jim so eloquently put it, deductive reasoning can lead you to
think the moon is green cheese. Logic is a wonderful thing, But it
can also be a trap if you're not very careful with the starting
assumptions. basing a statement of "truth" just on appearances or
deductive reasoning is a really great way to get things very very
wrong.

As this point, I would just like you to admit that you were wrong.
It?s four days ago that you told this forum that sulphuric acid is
not carcinogenic. You just repeated it. I am sorry, and I do not
want to insult you either, but you have no credentials of speaking
about this and you are wrong.

Leach Webb

50 
Wow. Sodium and hydrogen are very closely related?

Don’t you know that? Take a look at the periodic table.

I asked you what your credentials in chemistry are. No answer.

Perhaps the key here is that while different closely related
elements may have similarities in their chemical behavior,
electron shells or bonds, etc, that's very different from saying
they have similar behaviors in relationship to human health risks.

What do you know about that? Please cite your credentials. I think
you simply do not know what you are talking about.

Substituting a sodium atom for a hydrogen one is indeed a large
and important change, despite what you may have learned in middle
school. 

If you learned this in middle school, then I suggest you graduate
to a high school level chemistry course.

There is no need to go any further with this. I gave you my
credentials, you are just insulting me. Please treat people with
decency. I find your attitude to be extremely disrespectful.

Leach Webb PhD, which you chose to ignore because it does not fit
your improvisations.

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