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Is there a universal NIOSH definition of "inert"?


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Recent controversy over what MSDS may mean by "inert" led me to search

for the NIOSH definition. I found it at:

 

http://www.ilpl.com/msds/ref/niosh.html

 

If it does not come up at first, you may have to reboot and try again.

 

It may or may not be required to specify on the MSDS how much of a

material is inert, but when it is specified, the official NIOSH

definition of "inert" is as follows:

 

 

Definition

An inert chemical substance is one that is not generally reactive.

This is a synonym for "inactive" with respect to chemical reactions.

 

Additional Info

In the periodic table of the elements (graphic omitted), the inert

elements are the noble gases, helium (He), neon (Ne), argon (Ar),

krypton (Kr), xenon (Xe), and radon (Rn). Nitrogen (which occurs as N2

gas) is also considered inert:

 

 

These elements are unreactive because they are very stable in their

naturally occurring forms. While some of these can be made to react

chemically, their compounds are usually not very stable (except for

nitrogen). The term inert atmosphere is usually used to denote a

nitrogen or argon atmosphere in a container.

 

Chemical compounds can also be considered inert. For example,

poly(tetrafluoroethylene), better known by the DuPont tradename

TeflonTM, does not react with most substances. Likewise, sand, SiO2,

is generally unreactive.

 

We can also use the term to describe reactivity towards particular

substances. For example, mercury reacts with aluminum metal (which is

one reason why it is illegal to transport liquid mercury by aircraft)

but is inert towards iron metal. Carbon dioxide is inert to many

chemical reactions, but reacts violently with alkali metals such as

sodium and potassium. Using a carbon dioxide fire extinguisher would

be a VERY bad idea for a sodium metal fire!

 

 

MSDS Relevance

Inert materials are good choices for chemical containers. For example,

acid waste should not be stored in metal drums because these will

quickly corrode. However, glass or polyethylene containers are inert

to most acids.

If a chemical spill occurs, one may need to clean up the spill by

using an inert absorbing material such as vermiculite or sand. The

MSDS will usually recommend a specific material, but not always. If in

doubt, phone the manufacturer listed on the MSDS.

 

End of NIOSH definition.

 

The argument that an inert material in one application may be active

in another is true for certain materials, but that will be stated in

the MSDS when it is true. It is certainly not true for most of the

materials we use in developers and the like. For us, if the term

"inert" is used without exceptions, it means "chemically inactive" and

thus cannot include such materials as salt, bromides, and the like.

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I've never had a bit of trouble with sodium carbonate from the pool store, but it would be very interesting to have a sample analyzed to find out just what the one or two percent "inert" portion consists of. The other worry is quantities of substances so low that nobody in the safety world cares about them, but that might affect film development so far as fogging or somesuch. My last developer blend contained such things as rose hips from the vitamin C and whatever coating is on aspirin, but I just filtered out what wouldn't disolve and, again, no problems. In 35 years of photography I've never lost a roll due to a chemical problem, but I can't say the same for "photographer problems".
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Patrick;

 

We can keep going round and round on this. Teflon is inert. Ok, if you handle teflon powder, then go outside and smoke a cigarette, the powder gets into the paper from you hands, is vaporized (no reaction here AFAIK) and into your lungs where it causes flu like symptoms and other respiratory distress. So what. NIOSH or whoever says it is inert. Not under all conditions.

 

Sodium chloride is inert in a house fire. The firemen don't have to worry about your salt in the cupboard. It is defined as inert by NIOSH and MSDS then, I guess. IDK. Kirk Keyes is the expert.

 

I am a research chemist with about 40 years of practical experience. Others match or exceed my experience. Probably most exceed my knowledge of chemistry. IDK. I know that I take lab precautions and use chemicals as pure as possible. I take safety very seriously and also repeatability and quality very seriously. I see glaring loopholes in almost every 'comparison' 'formula' or 'test' on this forum or in photo magazines, because they are being done in many cases by rank amateurs. I hasten to add that I have seen some superb work here and in magazines for both design of experiment and data, for example the recent work by James Dainis on another thread.

 

Please read Danny's post about fixer solution problems with a 'known' good formula from Anchell's book. Water of hydration ruined his mix, if our tests are right. He did a good job of finding the problem and solution.

 

I don't know what your background is, but I have had 7 years of college taught chemistry in addition to the experience mentioned above, and I don't want to give ambiguous or imprecise information to people untrained in chemistry or the scientific method. With my education, I have trouble enough understanding NIOSH and MSDS definitions and I have trouble enough with balky photographic film, paper, and solutions.

 

Take Kirks word for it. Impurities can be bad for photography but inert otherwise. Also, consider that volumetric measurement of solids is not a good laboratory practice, and in addition there are photographic parameters beyond H&D curves and picture tests.

 

Lets stop beating a dead horse. Or, lets let Kirk's word be the final arbiter for these MSDS and NIOSH things. I respect his judgment and his knowledge.

 

I built a bridge out of balsa wood for my model trains, and it works fine. I would not even consider building a bridge for Amtrak. Think about the implications in this parargraph. 'Nuff said.

 

Ron Mowrey

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Ron,

 

Correct me if I am wrong, but,

 

As to unexpected, but often predictable, consequences... like the noble gasses, "di-hydrogen monoxide" is also "inert" according to OSHA but it will kill you [dead; deceased; kaput!] if you try to breathe it in quantity.

 

In pure liquid form at room temperatures it will not conduct electricity - but if only slightly contaminated it generally will.

 

It may not be normally flamable but at extremely high temperatures can break down into a flamable component (H2) and a component that, though not itself flamable is very reactive (O[2]}

 

Nuff said

;-)

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Dai, Conrad;

 

That is exactly my point.

 

Put something unknown into a photographic solution and you might lose your photographs. They might look good, but might have a microscopic fault that is not apparent to the naked eye. Indeed, if you didn't have a side by side complete comparison with some sort of reference, you would not know what, if anything, went wrong.

 

I have tried and tried to bring to your collective attentions that micro imaging is important. Edge effects make or break a photographic system, not macro effects such as an H&D curve.

 

A side by side print comparision of a sharpness chart might resolve your uncertainty about a given process or chemical, but as I said over and over, "If you are happy, that is what counts". I'm just adding on two caveats "You might not know what you are missing" and "Someday something might go wrong".

 

I hope you have all read Danny's fixer problem thread by now. It is quite relevant to this entire topic.

 

I am only pointing out that it is the uncertainty that is the problem.

 

Oh, Conrad, BTW, is your carbonate anh or monohydrate? Do you know? My bottles from Aquachem don't state. They could leave the plant in sealed containers as anh. and now be half way or something in between to becoming the monohydrate. They might contain bicarbonate or lye as contaminants as well as sea salts such as Magnesium Carbonate and Calcium Carbonate, etc. as well as halide salts. Kirk Keyes has made a significant contribution to this topic. We should not ignore his comments about purity, NIOSH and MSDS.

 

Ron Mowrey

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Patrick - I am not convinced that this web page link you give really contains a NIOSH definition of "inert". While it does talk abont MSDSs an NIOSH, this site looks to me to be a collections of safetly definitions that someone has put together. Perhaps you can find something more authoritative from NIOSH directly...

 

I know this will get us away from photography and into hazardous waste, transtortation, and other safety issues, but anyway...

 

Lets look at the first sentence of your "Definition - An inert chemical substance is one that is not generally reactive. This is a synonym for "inactive" with respect to chemical reactions."

 

The first part of the sentence is good, I think they missed the point with the second one thought. The word to pay attention to is "reactive". That is a very important word in the safety field - and it has a legal definition. The following is from a DOT website:

 

Reactive wastes are solid wastes that exhibit any of the following properties as defined at 40 CFR 61.23(a):

 

?it is normally unstable and readily undergoes violent changewithout detonating.?

 

?it reacts violently with water.?

 

?it forms potentially explosive mixtures with water.?

 

?when mixed with water, it generates toxic gases, vapors or fumes in a quantity sufficient to present a danger to human health or the environment.?

 

?it is a cyanide or sulfide bearing waste which, when exposed to pH conditions between 2 and 12.5, can generate toxic gases, vapors or fumes in a quantity sufficient to present a danger to human health or the environment.?

 

?it is capable of detonation or explosive reaction if it is subjected to a strong initiating source or if heated under confinement.?

 

?it is readily capable of detonation or explosive decomposition or reaction at standard temperature and pressure.?

 

?it is a forbidden explosive as defined in 49 CFR 173.51, or a Class A explosive as defined in 49 CFR 173.53 or a Class Bexplosive as defined in 49 CFR 173.88.?

 

(End of info from DOT site.)

 

That is the definition of reactive, and it goes hand in hand with materials that are "ingitable", "corrosive", and when placed together "incompatible".

 

You say, "The argument that an inert material in one application may be active in another is true for certain materials, but that will be stated in the MSDS when it is true."

 

That's somewhat true! Several sections in the MSDS state this info. Section 5 - Fire Fighting Measures, Section 7 - Handling and Storage, Section 10 - Stability and Reactivity (that's that word "reactivity" again) all have this type of info. But you can see by reading them that they are talking about safety. Not chemical analysis. They will not have a listing of what is inert in a photographic application vs. a cosmetic application. They are concerned with things like what happens when the fire fighters add water to this material.

 

Once again, I think your idea that a document designed for safety can be used for chemical analyses is off base.

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Conrad - I used to work at a lab that tested soda ash (bulk sodium carbonate) before it was shipped to China (where it was probably purified to sodium carbonate and sent back to the USA).

 

I went to the loading dock at the port once, and the soda ash arrives in traincars, it is dumped out the bottom of the cars onto conveyor belts, carried into a large warehouse (300x100 ft I think), piled up tens of feet and held there until a ship arrives. When the ship got there, the material was put back onto the conveyor belt, and transported on to the ship. Not a good method if you are trying to keep something from getting contaminated with dirt, but, again, this was bulk soda ash (like what is in the pool pH plus chems).

 

We did the tests specified to meet the certifications required for soda ash. The tests were simple tests, much the same as described in the other thread. Unfortunately I don't have a copy of the specifications, but I can tell you they were pass/fail tests. Things like moisture content, a turbidometric (nephalometry - see the other thread where I descibed this test) for halogens (choride, bromide..), insoluble matter and other tests in this vein.

 

But as you say, your pool chems have been meeting your needs, so why not use them. Ron's concern is that some people have higher needs, and materials like this may not meet those needs without a lot more testing.

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Ron - Nice piont about teflon, but I can tell you that there is a chemical reaction going on there. The teflon is being oxydized (burned) they the heat of the cigarette, and it is producing hydrofluoric acid. Not something you want in your lungs. In addition to testing soda ash years ago, I also did plastics identifications - one of the tests for identifing teflon and other fluorocarbon plastics is to burn them with a bunsen burner and test the pH of the vapours that are produced. When most things burn, the vapors have a mildly acidic pH (4-5), when fluorinated materials burn, they have a very low pH, about pH 1 or so.

 

Since we've all realized that MSDSs are for safety info, let's look at a few lines from Dupont's MSDS for Telfon - "Hazardous decomposition products including carbon dioxide, carbon monoxide, hydrogen fluoride, toxic gases or particles may be formed during combustion. These products may cause severe eye, nose, and throat irritation or toxic effects. [...] Wear self-contained breathing apparatus. Avoid breathing decomposition products."

 

And since we're on the subjust of inert materials, try heating up some concentrated sulfuric acid in a teflon beaker - it will make a big mess - but probably because the teflon melts at those temperatures. But incompatable materials nonetheless.

 

By the way Ron, thanks for the title of "expert" - but I'm not really. I just have more experience than most others here as I have to use tools like MSDS and chemical analyses on a daily basis.

 

It sounds to me like Lex could give some more input as well on this subject as well.

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Kirk;

 

I knew about the HF, but it was my impression from an article that there were effects from inhaled CFs in the lungs that were absorbed into the blood stream. Something that gave the flu like symptoms that could not be explained by HF. HF would have just caused serious lung problems.

 

The symptoms described among teflon workers went beyond HF inhalation or absorption.

 

Anyhow, this effect was known long ago. Even overheated teflon coated cookware can cause problems.

 

Thanks for the contributions and clarifications.

 

Ron Mowrey

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I've spent a fair amount of time pondering edge effects and acutance, since that's the main battle with my PPD formulas. Those effects are really important, but I don't ignore the H&D curve either. The problem is that I use a variety of chemicals, sometimes Kodak, sometimes Photographer's Formulary, and sometimes grocery store and pool chemicals. The number of potential combinations, and possible effects of contaminants, are huge. Unmanagable in fact, and I don't have the time or inclination to do the tests. I like to think I have enough experience to spot problems quickly, and identify the cause, but there are certainly subtle things that could get by me. The reason I don't lose much sleep over any of this is something I've stated in other posts- I don't experiment with images I consider important. I have a few very specific film & developer combinations I use when the results are important to me. Specifically, FP4+ with FX2 (made from PF chems), and Tri-X in HC-110 dilution B. Even though my PPD formula seems to be working well, I don't yet treat it as a bulletproof receipe. I need to know how it ages, how it works with a variety of films, and how it works with "real" chemicals, vs the supermarket stuff I started with. Bottom line is that I'm pretty conservative. Remember though, the more knowledge you have, the more potential problems you can probably identify. That should be balanced by the fact that we have remarkably few reports of anyone actually having a problem due to contaminants. BTW, IDK on the type of hydrate, and I should!
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All of the concernes over chemical purity are valid in theory, but in my personal practice are simply not a factor. I've made up liters of highly concentrated developers of Patrick's formulation, and have had the most consistent results I've ever had with any developer. These developers are made up with TEA and PG, and are very active, requiring only 10-20ml of concentrate per roll or 8x10 sheet of film, making them very economical in addition to being very stable, and between the two formulae, I can make up any kind of developer I need, including paper developer. I know that you are arguing a specific, theoretical point about what CAN happen when using chemicals of unknown purity, but I thought I'd share what HAS happened. While I don't own a balance, I do have a densitometer, and Kodak Control Strips with which I measure the activity of my developers periodically, and I can see that these developers are a lot more stable than the developers we used at the pro lab where I worked. These developers just don't move, even with my teaspoon measurement of Ph Plus and 20 Mule Team Borax. I know; I'm not a chemist and have no business discussing these issues with men of your collective education, but I believe that it was for people like myself, dedicated amateur photographers, that Patrick developed these formulae, and in my case, the formulae work as intended with absolute predictability. Its very easy and safe to recommend only the purest chemicals available, but I encourage you to find a failure in practce before condemning the methods and chemicals that Patrick suggests.
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Re: the decomposition of hot Teflon -- I believe that in addition to oxidation, Teflon can be "heat-cracked" to revert to the monomer and related compounds. Tetrafluoroethylene should be a strong electrophile and not very healthy! I'm not sure what the precise "cracking" conditions are.

 

And Kirk -- Is pool-grade sodium carbonate really just unrefined soda ash? Obviously the pool stuff ain't analytical grade and there will be impurities, as we've been discussing for a long time, but I've never seen the claim before that it is completely unrefined material.

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Jay;

 

That is good information to have, and the first I have seen here that has some reliable checks and balances, the control strips.

 

Thanks for that contribution.

 

Do you have any information on image sharpness and granularity to share? I would be very interested in your data.

 

BTW, did you see my post in your paste thread? I chimed in too late, but added some information you might be interested in.

 

Ron Mowrey

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Rowland, thank you for the goo information in the paste thread, it is a real priveledge for me to be able to discuss my hairbrained schemes with a man of your education and experience. Regarding the developers I've been using, I'm afraid I don't know how to measure sharpness and granularity quantitatively. I have no resolution test targets, or a microscope. If there is a procedure that I could perform to generate the information you want, I'd be happy to do so, and send you the print/negative for evaluation. I will post scans of 8x10 prints from 6x7 negatives when my scanner comes back to life, but I can't imagine that they will have any quantitative value.
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Jay,

Good question - I have been hinting at that, haven't I? I was trying to be lazy and hope that someone would do that research for me! But since you called me on it, let's look into soda ash some more - check out this web site:

 

http://www.ocichemical.com/webapp/ociapp/products/prodfamily.jsp

 

Check out the second product - the OCI Lite. It is decribed as "OCI Lite? is particularly useful in the production of granular detergent type products where high bulk is desired and the product must remain free flowing in the presence of liquid wetting agents. It is also the product of choice for many water treatment applications..." This is what I believe your pH plus pool chemical is (note water treatment suitablility).

 

Click onto the product sheet and there is a list of specifications, scroll half way down the page to the specs and typical assay for "OCI Lite":

 

Sodium Carbonate (%Na2CO3) 99.2 minimum 99.80 Sodium Oxide (%Na2O) 58.1 minumum 58.40 Sodium Sulfate (%Na2SO4) 0.15 maximum 0.085 Sodium Chloride (%NaCl) 0.09 maximum 0.03 Water Insolubles, % 0.05 maximum 0.03

 

OK - Here we go. That's a little more precise and descriptive of our product than the MSDS. Here's the link to the MSDS for this product:

 

http://www.ocichemical.com/webapp/ociapp/products/msds_us.pdf

 

The MSDS lists the content of sodium carbonate in the soda ash as "100%", but as we can see from the product specification above, that the sodium carbonate content of this soda ash product, is NOT "100%". In fact, it can be a MINIMUM of 99.2%.

 

The manufacter does say that 99.80% is a more typical value though. I want to point out that even though they did not state this, I bet the manufactuer does not worry if they have an assay that is OVER 100% -I bet that they may not sweat getting a 100.3% assay.

 

So now note that the choride content for this product has a maximum spec of 0.09% sodium chloride (that's 900 parts per million) - nearly 0.1% . I just looked at a bottle of Mallingkrodt anhydrous sodium carbonate, analyzed reagent (AR) grade, and it is 0.0006% - 6 parts per million. That's quite a difference between these two products. Now that we have some actual, working specifications for this one product, I'll let Ron let us know if this chloride content is significant, photographically speaking.

 

Also note the water insolubles - spec'ed at 0.05% - that's 0.05 grams in every 100 grams of the product of what most of us would call "dirt".

 

Looking over the specifications for OCI soda ash - the OCI Dense product actually has a slightly lower specification and typical concentration for choride than the OCI Lite product. Perhaps we should be looking to glassmaking factories for our soda ash supplies instead of pool chemicals...

 

Also, if you really want to get some of this stuff cheap, read closely to the product specification and you will see that it can be purchased in several different sized containers - 50- and 100-lb. net weight paper bags, Bulk trucks, Jumbo hopper rail cars, and Ocean vessels! ! ! ! You probably get a great deal on the ocean vessel sized lots! !

 

Ron and Jay mention using the purest chemicals possible. I would like to point out that this is not really a proper approach either. What is needed are chemicals that meed the specifications for your needs. There is no point in paying extra money to get an "ultra pure" greade of any chemical if you do not need it. It is very typical for labs (and I suggest photographers too) to buy the grade that just meets the specifications for your needs. Grades that do not meets the specs needed may have problems, and grades that greatly exceed you needs waste money.

 

Let's look at the specs for photograde POTASSIUM carbonate that were given by Bill C in an earlier thread: http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=008Yy1

 

Bill gives the ANSI spec for photograde POTASSIUM carbonate as 0.06% (600ppm). Assuming that photograde sodium carbonate has a similar spec to the potassium carbonate, it is slightly under the OCI soda ash limit. If you get a "typical" batch of OCI Lite soda ash, you are probably OK choride-wise (but you may not be so lucky with insoluble matter...)

 

So maybe in this particular case, things DO work out - but I think that the point here is that unless you do the research necessary to determine these what your needs are and if the materials meet those needs, you may have some real issues and not know where they are comming from and you may have other issues that you can not even try to quantify.

 

 

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Jordan - you asked specifically about "unrefined" - I didn't mean to imply that the material is what one may consider "unrefined". I suspect it is "minimally refined".

 

Even if it is dug or pumped straight out of the ground, there is still some "refining" going on. I think in the other thread I talked about how soda ash (and in my example of the potash mine near Moab, UT) does have some refining steps by using evaporationg ponds to recrystallize solutions of the material. This is certainly considered to be refining.

 

But if you mean that there are special chemcial reactions that are being performed on the materials before it gets into the pH plus bottle, I suspect they are really minimal. You know there is no real reason that they can not actually be adding certain chemicals to the evaporating ponds to "clean-up" the product, but I don't really know the details of the process that well.

 

One thing though - I'm sure the soda ash is dried to remove as much moisture as possible - to make the material more concentrated for shipping needs. Why transport all that water to China or when shipping it to the pool chem place? If they need water there in it, they can add it! So, there's one refining step that I know is done.

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Jay;

 

Thanks for the kind comment. I'm just happy to help, and I don't think I'm anything special. I've just had a lot of experience in this area. You each have your own area of expertise.

 

Kirk;

 

Thanks for the lead in. An impurity level of 0.1% of NaCl in a particular developer that I know of, at the level of Sodium Carbonate used as buffer, would just about DOUBLE the level of NaCl in the developer and render it entirely unfit for use. I can't give more details, as the developer is proprietary, but the results would change curve shape and speed drastically.

 

I would like more clarification on the Na2O as well Kirk. If that is present in any large amount, the resulting solution would be more alkaline than pure Sodium Carbonate. That could be detrimental as well. The pH and buffering capacity could change from batch to batch.

 

Also, in your comment about using pure chemicals, of course I don't mean that one should use analytical grade. You are entirely correct in stating that the purity should be as high as needed for the purposes intended (to paraphrase your remark). My feeling at the start of this was that I had a strong doubt that 'pool grade' sodium carbonate was pure enough for photographic use. A photographic grade chemical is pure enough for me.

 

My bottom line though is that Na2CO3 as you have posted above would probably be entirely unsuitable for many developers due to NaCl variations and Na2O variations, as well as the grit introduced by insoluable materials. This would not be the case for all developers but rather would have a different effect on every photographic film and paper to a different extent. If it was consistant from batch to batch, you could work around it, but if not, it would become a real hassle. Someone designing or using a developer from one batch could see a discontinuity if he changes batches. This is what I wanted to warn about.

 

Thanks again Kirk for an excellent and most helpful post. You are quantizing the things that I have been trying to make people aware of.

 

Ron Mowrey

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Ron - you ask about the Na2O content. That's just another way of assaying the soda ash. Actually it is really common in assaying minerals or materials that are made from minerals, such as lime, cement, concrete or rocks themselves. It makes the assumption that the material has been heated up to say 1000F to breakdown any minerals to simpler forms so that they can be analyzed. Especially when working with things like concrete or cured cement, it makes things much easier by doing this. It removes the water (and carbonates in things that contain lime like soda ash) and the material gets much weaker. (Here's something to toot my own horn - you may have figured out that I used to do this type of analysis too. I did. I actually did the analysis on the original mortar that was used in Crater Lake Lodge. It was analysed so that they could duplicate it when the reconstruction of the lodge was done in the 1990s.)

 

The soda ash assay had an entry for sodium carbonate content - that assay is probably performed by titrating a known, dried at a specified temperature (maybe 285C), amount of the soda ash against an acid that has a known normality - something like 1.0 N hydrochloric (I'm kind if guessing on the actual normality - it could be 0.5 or 0.1N).

 

The Na2O assay is kind of a simplified way of looking at the soda ash - it assumes that you only are looking at the sodium content. This test is probably done on an atomic absorbtion (AA) or an emission spectrophotometer (ES). You dissolve some of the material in water and dilute acid and suck them into one of these big machines. The machine aspirates the solution into either -

 

1) an air/acetylene flame and measures the aborption of the amount of light from a sodium emission lamp that is focused through the flame (AA method)

 

or

2) you aspirate it through a plasma jet which rips the electrons off any atoms that pass through the jet and the machine then measures the light given off as the electrons fall back into their orbits (ES method).

 

(I used an AA for the Crater Lake Lodge mortars.)

 

Once you have the sodium content, you report the result back as the simple oxide form of the metal, e.g. Na2O, K2O, CaO, MgO, FeO, SiO2, MnO... As I said, this is common in that type of industry.

 

Actually, you kind of want to worry about the Na2O being present in large amounts - it's really the sodium carbonate there (note that the spec says 58.1% MINIMUM). So it's not something that's detrimental, it's just another way of figuring out an assay of a material.

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Conrad mentions above that he has been pondering things such as microdensitometry. And Ron brings it up as well as a major part of his arguement.

 

Does anyone here have a microdensitometer? I know that Dr. Richard Henry used one in his classic book "Controls in B&W Photography". (Side note, this book is a must for anyone that is even remotely interested in the types of subjects that we have been looking into here lately.)

 

I would be interested in hearing from someone that has access to one or actually owns one. Perhaps there is a revenue source out there for that person by doing some testing on our home-brewed solutions?

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Kirk;

 

Thanks for the clarification on Na2O. I didn't think it could be there as an impurity for long. You would end up with NaOH pretty darn fast.

 

I am really honor bound not to disclose formulas, for anything, but I guess I can tell you that any chloride or chlorobromide paper will be affected by the variations you are talking about. Usual papers use NaCl as one of the antifoggants, and it does not take much to alter speed or contrast. The variation you mention is ~15% in one very common formula at the carbonate level used, and is about 45% for another paper developer which is less commonly used. It would be about 30% in another paper developer formula which has been discontinued.

 

Hope that helps.

 

On the subject of microdensitometry, I think you can see how edge effects affect sharpness of an image. It also affects the micro H&D curve vs the macro H&D curve. The curve shape you usually plot is a good test for a given film, but if the developer is misperforming, micro tests are needed to quantify the error and diagnose it.

 

KI released by films changes edge effects, so if KI is too high or too low, this effect varies. Bromide varies the effects of KI being released by changing antifoggant restraint levels. The pH of the film drops very rapidly during development, and the buffer raises it. If the pH fluctuates too fast or unpredictably you get varying antifoggant rates and varying restraint rates. The ratios of silver complex types and amount are governed by solvation rates which depend in part on pH and silver halide solvent ionization etc.

 

Bunch of blather, but what it amounts to is that development is rather complex in films and can be totally upset by rather small changes sometimes, and those changes can be invisible to casual detection methods.

 

Ron Mowrey

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Kirk, you beat me to it! I was going to ask if anyone had or had access to a microdensitometer. I own just about every tool known to man, but I'm afraid that one isn't on the list. Heck, I've never even seen one. For now, all I can do is take great care in printing, and look at details and test targets under a good microscope. BTW, I've found little correlation between what you see under the microscope, and what you get when printing, probably due to illumination differences.
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The definition I quoted is from the glossary of terms and is the NIOSH definition of inert. You can reach that glossary from the URL I provided. The definition does not say that Teflon is unconditionally inert. Look again. Dihydrogen monoxide by any name is not listed as inert, nor should it be. I don't remember how all this got started, but I do know that every time I try to explain my position, someone else tells me that is not really my position. Phooey!

 

Lex, I have been called out about my background. If I may send it directly to you, I will, and will let you decide if it should be made public. Nobody will believe it in any case, but I can provide it if need be.

 

Yours in brotherly love,

 

Pat Gainer

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