Experiments with Metol and ascorbic acid.

Patrick;

I'm going to take an extreme case here but bear with me.

Lets assume that you have Borax that is 10% impure, or onlly 90% pure! Lets also assume that the impurity is Sodium Chloride.

A saturated Borax solution will have less Borax in it than expected due to the common ion effect. This causes the less soluable of two sodium salts to precipitate more than predicted.

The 10% Sodium Chloride would become MORE saturated in solution and therefore the impurity level would be increased.

So, your saturated solution is less pure than the starting example.

This hypothetical example shows what you can do to yourself if you don't know the basic guidelines of what you are purifying or how you are purifying it.

Now, if there were a less soluable sodium salt, such as Sodium Aluminate (IIRC), it would concentrate in the solids that remained behind. So the precipitated Borax would end up with more of the alumiate salt.

Either way, you can make things worse.

PE

Photo Engineer said:

Patrick;

I'm going to take an extreme case here but bear with me.

Lets assume that you have Borax that is 10% impure, or onlly 90% pure! Lets also assume that the impurity is Sodium Chloride.

A saturated Borax solution will have less Borax in it than expected due to the common ion effect. This causes the less soluable of two sodium salts to precipitate more than predicted.

The 10% Sodium Chloride would become MORE saturated in solution and therefore the impurity level would be increased.

So, your saturated solution is less pure than the starting example.

This hypothetical example shows what you can do to yourself if you don't know the basic guidelines of what you are purifying or how you are purifying it.

Now, if there were a less soluable sodium salt, such as Sodium Aluminate (IIRC), it would concentrate in the solids that remained behind. So the precipitated Borax would end up with more of the alumiate salt.

Either way, you can make things worse.

PE

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The basic guidelines of Technical grade borax powder are well known, and the worst case I have seen is guaranteed to have less than 700 ppm of chloride. Under what circumstances could that amount of chloride NOT be dissolved in the first solution? I am depending on the total chloride, sulphate and iron which total 1330 ppm max in the original charge of borax to be dissolved in the first charge of water, 95% of which will be removed by decanting it. That solution certainly would yield a more contaminated borate powder than the original if it were evaporated. I would in fact be happy if it had only the soluble impurities and no borax. Instead, it will be discarded or used for drain cleaner or one of several other household uses. How can what remains in the undissolved borax not have less chloride than it had before? What if it does have more insoluble impurity? I am not using the insoluble impurity that remains. I am making a second saturated solution from it, leaving insoluble impurities behind. The second saturated solution removes doubt about hydration of the powder and MUST have smaller percentages of chloride, sulphate and iron. Why, in the name of good science, don't you read thoroughly what I wrote?

Patrick, using the simple principle of solubility and the common ion effect, I have explained to you how you can either concentrate an impurity in the mother liquor or in the solid. It is that simple. To do what you are describing, you must know what you are doing. If I cannot explaine some simple facts of chemistry to you, then I'm sorry.

You have to know what you are about, before you undertake it.

And, I said that what I had given was hypothetical, but nonetheless, your procedure as outlined will concentrate all halide and phosphate impurities along with other soluable sodium salts in the concentrated Borax solution.

I'm sorry, but that is a chemical fact.

PE

Here is an example. Let us assume compund X is 90% pure and dissolves in water at the rate of 50 g/l. It contains Y which is soluable at 100 g/l as an impurity.

Therefore, 50 g of X contains 5 g of Y.

If you take 100 g of XY mixture and place it in 100 ml of water, you will dissolve 50 grams of X and ALL OF Y. This means that the solution is now a saturated solution of X which is now 10% impure. By using bad procedure, you have doubled the impurity.

If you are after the solid, it is more pure than that in the liquid, but if you assume a third ingredient Z which is less soluable than X, then you have concentrated the Z in the solid as well.

Do you understand?

PE

Photo Engineer said:

Patrick, using the simple principle of solubility and the common ion effect, I have explained to you how you can either concentrate an impurity in the mother liquor or in the solid. It is that simple. To do what you are describing, you must know what you are doing. If I cannot explaine some simple facts of chemistry to you, then I'm sorry.

You have to know what you are about, before you undertake it.

And, I said that what I had given was hypothetical, but nonetheless, your procedure as outlined will concentrate all halide and phosphate impurities along with other soluable sodium salts in the concentrated Borax solution.

I'm sorry, but that is a chemical fact.

PE

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And it is also a chemical fact that the solution I am keeping is not the solution you are talking about. I am using the sediment from it to make a second saturated solution which cannot, according to your own lecture, be as impure as the first because the first has dissolved and carried away 95% of the soluble impurities. You apparently do not know what I am doing. Read it again or forever hold your peace on this subject. I gave a numerical example illustrating exactly what tou are preaching. The first saturated solution carries with it the soluble impurities in the 200 grams of borax, while dissolving only about 40 grams of borax. The remaining 160 grams of sediment contain only about 5% of the original soluble impurities. The first saturated solution is discarded or used around the house. The 160 remaining grams of borax are sufficient to make at least 3 liters of saturated borax solution. Have I said anything wrong so far? I'm beginning to think you are the one who flunked out of chemical engineering. This method of using differential solubilities to purify is very old. If I had a solvent that would dissolve everything but borax, I could eventually get very pure borax without losing any, but it would not be in the sediment. It would be in the last saturated water solution I made.

gainer said:

the specs required of Photo Grade borax.

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Author: American National Standards Institute.
Title: American national standard specification for photographic grade sodium tetraborate pentahydrate and sodium tetraborate decahydrate.
Published: New York, N.Y. : American National Standards Institute, c1982.
Physical Description: 3 p. ; 28 cm.

Subject (LCSH): Photography --Standards.
Photographic chemicals --Standards.
Other Name: National Association of Photographic Manufacturers, Inc.
Other Title: Specification for photographic grade sodium tetraborate pentahydrate and sodium tetraborate decahydrate.
Notes: Caption title.
"Revision of ANSI PH4.230-1976."
"ANSI PH4.230-1982."
"Approved February 26, 1982."
Other Identifying Number: ANSI PH4.230-1982

Come to think of it, people in Virginia use it on Smithfield hams. The ham must be soaked in water for quite some time, the water removed and replaced by fresh, and the process repeated several times to get the salt to the point where a person can safely eat the ham. And you pay a lot for the privilege of doing it.

gainer said:

Come to think of it, people in Virginia use it on Smithfield hams. [...]

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Are you talking about salt (sodium chloride), borax, or perhaps TSP (trisodium phosphate) here? It's hard to tell.

Neanderman said:

Author: American National Standards Institute.

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We all know where to find the specs. We just don't have a copy of it. Perhaps you do, Neanderman?

gainer said:

And it is also a chemical fact that the solution I am keeping is not the solution you are talking about.

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I missed that you were tossing the first leaching of the tech grade borax on the first reading myself. I did not find it clearly stated it was discarded. Anyway...

I still have issues with using saturated solutions as a form of calibration. It's just so tricky using them as thye are so dependant on temperature. It's just so much simpler to weigh something out and dissolve it in solvent. I can't think of any analytical procedures where a saturated solution of anything is used as a "calibrated" solution. They are usually used as a reagent solution that is being added to a solution in order to supply an excess of a reagent, never to supply a precise amount. If you are careful and use good temperature controls and make sure you don't get your solution too cool and crash out your reagent, you could use a saturated solution as you describe.

But it really looks like a pain... Just buy a grade of high quality reagent and work from there. None of these mechanations to turn a sow's ear into a silk purse. (There, I was able to tie it back in with your ham comment!)

gainer said:

The basic guidelines of Technical grade borax powder are well known,

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Well known? - didn't you just point out that there are two different specs for the same grade of borax? Granular and powder - both called Technical Grade, have differing specs?? That's pretty precise!

Also, you say,

gainer said:

Let me point out that the highest grades I have seen specified by Rio Tinto and others guarantee the sodium tetraborate decahydrate equivalent to be between 99.9 and 105 or even 110 %.

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That's not the highest grade that you have seen. Technical grade is usually considered the lowest grade. Surely you read the assay that Mick listed for the results of his ACS Analyzed Reagent Grade Borax - it listed "Assay = 99.101%". (there was a url link here which no longer exists)

Let's think about that for a second to let it sink in... One grade has a precision of 5 digits, the other grade has a precision of 10%. Now which one should we consider to be the higher grade? I hope you answered this one by saying "AR Grade" to yourself.

Now if you are really determined to purify your own technical grade borax into the equivalent of reagent grade, then I would suggest incorporating the following suggestions:

First, boil your solution. And do it for a while, like an hour. It does not have to be saturated while you boil it - that would be a pain as the solution would want to crystallize out as you are boiling it. And it doesn't have to be a hard boil, just keep it near boiling for the hour. The reason is that you want to try and use the high pH and temp of the boiling borax solution to hydrate any silicates in the borax. This will help them drop out of solution and make them easier to filter out.

Second, filter your solution to remove insoluble matter. Get yourself a large (like a 20 or 30 cm diameter) Buchner funnel and some glass fiber filter paper. The Buchner funnel can readily be found on ebay for less than $20. Get a glass filber filter paper like Whatman GF/C which has a pore diameter of about 0.45 um. This will remove all particulate.

Third, after you've done your leach to remove the chloride and other things that are more soluble than borax, use enough water to dissolve your remaining borax so that it makes a saturated solution at a temp of about 80 to 100F. This way, after you've boiled your borax solution, you can let it cool down some to make it safer to handle, and then filter it with the Buchner and a vacuum to help it pull through the filter. So filter it when it reaches about 125F and the borax will stay in solution and not clog the filter.

So now you have a filtered solution of borax, with no insoluble solids. Since we dissolved enough borax into the liquid so that we would reach saturation at about 80F, we will get some crystals of borax precipitatating out of our solution when we get below 80F. Go ahead and cool it and hold the temp at your 63.6F. That's the hard part of your procedure - hitting that temp and holding the solution there until all the borax drops out of solution. Constant agitation from a magnetic stirrer would be good here. Let it sit at that temp for a significant period with the excess crystallized borax in the bottom of the container. When you think it's been long enough at 63.6F, then decant the solution into another bottle and store it at a temperature that is higher than 63.6F.

Chemically pure sodium tetraborate powder will assay as almost 200% chemically pure sodium tetraborate decahydrate because it can make that much decahydrate by absorbing water. You can look up the NF grade which has practically no soluble or insoluble impurities and you will find that as the decahydrate it will assay as between 99.9 and 110%. I don't know where you learned your chemical engineering, but I hope you didn't learn all they were teaching. Most reputable schools would be better than that.

You will not precipitate any water insoluble solids from technical grade borax decahydrate powder.

You are saying that if I don't filter my borax solution, it will have insoluble solids in it.

First, Virginia ham is cured with Sodium Nitrate and Sodium Nitrite, not with Borates! Again, chemicals are being mixed up and this mixup can cause a deadly accident if someone tries to make their own cured ham.

Second, Patrick, I read your posts, you did not read mine. I said that you could concentrate impurities in BOTH the solid Borate that does not dissolve and in the saturated liquor.

Kirk has described a sound laboratory method above. I described a scenario which you obviously did not read or understand in any way. It is a hypothetical case illustrative of what I'm saying to you.

PE

Kirk Keyes said:

We all know where to find the specs. We just don't have a copy of it. Perhaps you do, Neanderman?

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Try a library. That citation came from the Illinois State Library on-line catalog. I live in Cincinnati, my public library has some of the ANSI/ISO standards.

Ed

Photo Engineer said:

First, Virginia ham is cured with Sodium Nitrate and Sodium Nitrite, not with Borates! Again, chemicals are being mixed up and this mixup can cause a deadly accident if someone tries to make their own cured ham.

Second, Patrick, I read your posts, you did not read mine. I said that you could concentrate impurities in BOTH the solid Borate that does not dissolve and in the saturated liquor.

Kirk has described a sound laboratory method above. I described a scenario which you obviously did not read or understand in any way. It is a hypothetical case illustrative of what I'm saying to you.

PE

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I didn't say Virginia ham, I said Smithfield Ham. If you've never seen one, there's no use trying to describe it. I wasn't talking about the particular substancesto be removed, but about the method of removing...washing, in essence.

I know you can concentrate insoluble substances in the remaining solid and soluble substances in the saturated liquor. That is the purpose in making the liquor. When you dispose of the liquior, that disposes of most of the soluble impurity, leaving only that in the liquor adsorbed by the undissolved borax. When I make the SECOND batch of saturated liquor, It will have less soluble impurity than the first, in the example I provided, by a factor of at least 16.

I have accomplished two things by this rather simple procedure: I have a solution with less soluble impurity than if it had been made by dissolving the raw borax, whatever grade it started as, and I know the weight percentage of borax decahydrate with a certainty greater than you know the weight percentage of the dry powder, no matter what its grade, for the simple reason that sodium tetraborate could be in any of three states of hydration in the powder, but only one in the saturated solution. You can buy the NF Powder grade, which has as its only impurity =<20 ppm heavy metals and you will see that the guaranteed percent of Borax Decahydrate is 99.0 to 105.0. That uncertainty is due to the uncertainty of the water content, not the borate. Thus, if I have a saturated solution whose weight percentage I know to be between 3.95 and 4.05, I know as much about my measure of borax decahydrate as you would by weighing the powder directly. The slope of the curve vs temperature in that vicinity is about 1.6 wpc/decree C. How do you know the water content of the batch of AR you got after you've had it a while?

Neanderman said:

Try a library.

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I've tried the local state university. Nothing. I guess I need an interlibrary loan.

gainer said:

I didn't say Virginia ham, I said Smithfield Ham.

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Pat, I'm a Yankee. I'm not familiar with one of these hams. It was too obscure of a reference. I see they are dry cured and need to be rehydrated so they are fit for human consumption.

You said:

gainer said:

Come to think of it, people in Virginia use it on Smithfield hams. The ham must be soaked in water for quite some time, the water removed and replaced by fresh, and the process repeated several times to get the salt to the point where a person can safely eat the ham. And you pay a lot for the privilege of doing it.

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Your statement is unclear in respect to the previous dicussion. It's really easy to assume you are talking about "it" being borax.

When I make posts, I type them out as I would when speaking, and then I go back over them and reread them to look for where I can make them more clear and precise. I replace a lot of "it"s with the actual item name or decription so it reads more clearly.

By the way, Borax was used as a "bug killer" in the production of hams beginning in the 1880s or so - it keeps the "skippers" out, some kind of fly that spoils ham. The FDA does not allow this use, as we all know and with your propensity for talking about borax as a home remedy, who can tell what you are talking about?!

Both Viginia and Smithfiled hams are salted and cured in the Sodium Nitrate/Nitrite solutions. They may or may not be dried, I don't remember which is and which is not. Prosciutto hams are made much the same way by salt curing and air drying with no other treatment.

One type is soaked in water before cooking or is cooked in water that is discarded. The other can be eaten directly if properly cured and or smoked during the curing process. They may be 'cold' smoked or 'hot' smoked just as fish is often smoked both ways.

As for your procedure with Borax, yes, it requires repeated recrystallizaations to work properly and does depend heavily on the types of impurities present, but I stress REPEATED recrystallizations as you stressed. One sequence will often not work and this is what you have to understand. This involves so much extra labor and uses so much water (as I said in previous posts) that the user is well advised to buy pure product to start with or the cost will soar.

I think that this is going quite astray by trying to prove that lower quality materials can be used. They can work, but you can also pay a price in terms of quality that can bite you in many different ways as I have pointed out before.

I should add that not knowing the starting purity of an impure substance often leads one to using an incorrect number of recrystallizations. I had to run purity tests after each recrystallization that I ran in graduate school to prove the purity before I sent it out for analysis to get the 'final' purity verified. We did much the same at Kodak.

I remember one chemical that was so difficult to make and purify that they used the largest reactors to run it and ended up with a tiny bottle of photograde material at the end which was worth thousands of dollars, just to get the purity level needed. It was an ingredient that went into an emulsion.

PE

I have to apologise for being unclear about what happened to the first batch of saturate. I thought I had said "Throw it out or use it for drain cleaner". As for rewriting, you shold have seen the first three versions.

I know that you are doing things with home made emulsions that require much more precise measurements than does film development, where much of the time we do not know for sure what contrast we need in the negative, and in roll film, we must often strike an average and do the rest in printing. The use of borax, metaborate, carbonate qnd many other chemicals can often be done as a chef does his favorite recipes..a dash of this and a pinch of that. To my knowledge, I have never in over 65 years used borax where a measurement error of 5 or 10 % would make a noticable difference. As for the guaranteed limits of chloride, sulphate and iron in technical grade powdered borax, a fingerprint on a mixing utensil might have as much effect. I know for a fact that I cannot see enough diference from adding 50 grams of sodium chloride to a liter of D-23 to make it worthwhile, so I cannot see how 700 ppm in 2 grams of borax would do any damage, nor 600 ppm of sulphate when 2 grams of Metol carries more than that into a liter of working D-76. Insoluble particles are specified <400 ppm in granular tech grade but none in powder tech grade. I suspect the insoluble particles are sand, but who knows? If so, it's not one of those things a production line would want to grind to powder.

Patrick;

You are doing your measurements qualitatively using the Mark I Eyeball which in your case is now over 80 years old IIRC.

I did mine with the IB sensitometer and the Macbeth densitometer and did it qantitatively.

I trust mine, and I trust the differences that I have seen. Papers can sense as little as 100 milligrams difference in bromide or chloride concentration in a liter of developer. It affects speed and curve shape both. In some papers, it affects fog as well.

PE

Yes, but I was talking about film. I do use metaborate in paper developer, but that's a different animal from the one we've been discussing. I do have a densitometer that I designed and built that can read to .005. Besides, if the tech borax meets specs, a saturated liter would have at most about 0.028 grams of sodium chloride.

Kirk Keyes said:

Well known? - didn't you just point out that there are two different specs for the same grade of borax? Granular and powder - both called Technical Grade, have differing specs?? That's pretty precise!

Also, you say,


That's not the highest grade that you have seen. Technical grade is usually considered the lowest grade. Surely you read the assay that Mick listed for the results of his ACS Analyzed Reagent Grade Borax - it listed "Assay = 99.101%". (there was a url link here which no longer exists)

Let's think about that for a second to let it sink in... One grade has a precision of 5 digits, the other grade has a precision of 10%. Now which one should we consider to be the higher grade? I hope you answered this one by saying "AR Grade" to yourself.

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The highest grade I have seen from Rio Tinto specs is NF, a pharmaceutical grade, which lists only heavy metals at <20 ppm. The difference between Rio Tinto Tech granular and powder is ONLY in the water insoluble particles, which are <400 ppm in the granular and none in the powder. The variance in measurement of percent borax decahydrate is in the water content, which will vary with storage conditions due to changes in humidity. the same variance can occur in any grade, including AR.

Your AR grade assay was for a particular sample of known hydration

If a cheapskate is using alternate-sourced borax instead of 'photo grade' (or photo company supplied), for cost reasons, then there will be a limit to how much lab refining the cheapskate is able/willing to spend time/money on. A 4 liter Pyrex beaker probably costs more than some of my other stuff and more than my chemicals combined.

I may be in the cheapskate category, but I'm sure I spent more buying bulk chemicals than I could have buying packages of developer, because I would have more fun with the DIY approach.

I DO find the discussion of the science interesting, however.

gainer said:

The highest grade I have seen from Rio Tinto specs is NF, a pharmaceutical grade, which lists only heavy metals at <20 ppm. The difference between Rio Tinto Tech granular and powder is ONLY in the water insoluble particles, which are <400 ppm in the granular and none in the powder. The variance in measurement of percent borax decahydrate is in the water content, which will vary with storage conditions due to changes in humidity. the same variance can occur in any grade, including AR.

Your AR grade assay was for a particular sample of known hydration

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Pat - Did does Rio Tinto Technical Grade Powder really say "none" for the insoluble particles? That surprises me as there should be a limit of some sort - i.e a value given in parts per million. As an analytical chemist, I can say that there is always going to be a little of something in most everything... unless you are talking about homeopathic medicine. Did it really say None detected or something, and that is based on the method of analysis, but really doesn't mean that there is "none". Just that that test can't detect any.

The AR grade assay had absolutely nothing to do with a "known hydration". Infact, I doubt the hydration was even tested for. It was an "assay", a measurement of the material of interest.