Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 71,919   Posts: 1,584,805   Online: 1115
      
Page 5 of 11 FirstFirst 1234567891011 LastLast
Results 41 to 50 of 104

Article: Borax Project

  1. #1
    gainer's Avatar
    Join Date
    Sep 2002
    Posts
    3,726
    Images
    2

    Borax Project

    My Borax Project
    Borax is useful in many ways. Some of us worry about the purity of the commonly and cheaply available 20 Mule Team Borax. There is another concern in cases where accuracy of weight is important. Borax has 2 possible states of hydration, decahydrate and pentahydrate. If a 100 gram sample of pure borax has pentahydrate and decahydrate mixed, the assay will show a greater weight than 100 grams. If 5 grams of a 100 gram sample are the pentahydrate and the rest the decahydrate, no matter how purely the saple is composed only of sodium tetraborate and water of hydration, the assay will show 101.5 grams of the decahydrate. There is no way you can tell at time of collecting a sample from a large batch of pure mixture how much of each hydrate you are getting.
    A common solution to both problems is literally a solution. A saturated solution of borax at a given temperature contains a known weight of borax expressed as the decahydrate, whether the solid used to make the solution was penta- or decahydrate. If the solution was made saturated and separated from the solid at a low temperature, it will have a constant weight of borax per unit weight of solution at any (reasonable) higher temperature. The weight per unit volume will stay constant enough for most uses.
    A simple way to purify a large quantity of borax at the expense of a smaller amount is to make a concentrated solution in boiling water, allow it to crystallize at a temperature below that desirable for keeping, and decant the clear liquid and discard it or use it for cleaning. The soluble impurities in the original borax are presumed to be uniformly distributed in the liquid, so that if, say, 90% of the liquid is removable by decantation and/or fitering, the remaining impurities will be reduced by 90%.
    656 grams of borax decahydrate are soluble in a liter of solution at 100 C. If the temperature is reduced to, say, 15 C, there will remain only 37.9 gram in the discarded solution. The remaining 618 grams of borax has been cleansed of about 90% of its original soluble impurities and is sufficient to make 16 liters of borax solution.
    When I first proposed this approach it was considered by certain of our resident chemists to be a complicated alternative to paying the money for analytical reagent grade of borax and weighing it to the milligram, even though it is well known among other chemists and for the same reason I stated above that such a degree of precision is not warranted by the uncertainty of the state of hydration of borax. Then, to top it off, I had a senior moment and recommended the use of 10 times more of my borax solution than was proper for D-76. That was seen as proof that I knew not whereof I spoke. Furthermore I made the assertion that 10 times too much borax was not as bad as it might seem. In the process of defending my assertion, I found a variation of D-76 that I may (or may not) call "serendipitol". Serendipity is exemplified by the fellow who accidentally walked barefoot through a certain kind of animal excrement and discovered it to be an excellent cure of athlete's foot. I seem to remember that the animal was of the male bovine type.
    I made 3 liters of D-76, two with 10 times the prescribed amount of borax in the form of 425 ml of a 4.71% solution. To one of these were added 20 grams of boric acid crystals. The third liter was made as old-fashioned D-76, using 42.5 ml of the 4.71% borax solution. The rule of this game was to pretend I didn't know about the extra borax and treat it the same as store-bought. I shot 36 exposures of HP5+, bracketing plus and minus 1/2 stop. Any consecutive 4 frames had all three exposures. As it turned out, the nominal exposure was quite good in all three cases.
    I have three cases to show. Each one shows a low resolution scan of an 8x10 print to show its chiaroscuro and a high resolution scan of a portion of that print to show resolution and granularity. The one labeled "D-76" is Metol, 2 grams, hydroquinone,5 grams, 42.5 ml of 4.7 % purified borax solution, and demineralized water to make 1 liter. "D-76 B+" is Gadget's mistake with 425 ml of the borax solution. As cure of the resulting high contrast, I took a cue from more recent D-76 and added 20 grams of boric acid crystals per liter of the mistake and called it "D-76 BB". I used VC paper. I had the contrast turned all the way down for the D-76 B+ negative and no filtration for the other two. I set printing exposure for each print to make the whitest part of the fuzzy stuff in front of my great granddaughter's teddy bear the same.
    I got the expected high contrast from Gadget's Mistake, but grain and resolution were not seriously affected. Adding boric acid to make D-76 BB brought contrast back to near normal.
    Would there be a technical reason for making D-76 BB? Its pH is lower initially than that of traditional D-76 but its activity is nearly the same, at least on short strips. Its buffering capacity should be greater, both locally and overall, which should make a difference in the effect that different types of agitation make on gradations, but the effect may not be what one is looking for. In any case, it is another possible pictorial control.
    Gadget Gainer

  2. #41
    Murray Kelly's Avatar
    Join Date
    Jan 2007
    Location
    Brisbane, QLD. Australia
    Shooter
    35mm RF
    Posts
    429
    Quote Originally Posted by gainer View Post
    I'm posting the comparison that really counts, the one between SPF-3 and Rodinal 1+25. All I have to do now is find where I saved them.
    They are "hybrid" photos, using a flat bed scanner at 600 dpi to read 11x14 analog prints. If you print them to 8x10, you should view them from about 6 ft to get proper perspective.
    Now, there's a difference! Not like the almost too close to call Microdol-X comparison in the other thread on the 'dead' metol.
    I have to say, tho, I've never used Rodinal that strong and don't know if dilution is a factor. The tonality matches but the detail isn't there. SPF-3 looks good to me.

    Given the unusual solubility (amount and curve) my idea was to fractionally crystalise out the tetra and leave any more soluble contaminants in the supernatant. I didn't do it in the end. I merely weighed the plastic pots and contents, making a note under them and will reweigh when I need to open another one up for use. This assumes the contents were indeed tetra as stated on the MSDS to start with.
    Murray

  3. #42
    gainer's Avatar
    Join Date
    Sep 2002
    Posts
    3,726
    Images
    2
    Quote Originally Posted by Murray Kelly View Post
    Now, there's a difference! Not like the almost too close to call Microdol-X comparison in the other thread on the 'dead' metol.
    I have to say, tho, I've never used Rodinal that strong and don't know if dilution is a factor. The tonality matches but the detail isn't there. SPF-3 looks good to me.

    Given the unusual solubility (amount and curve) my idea was to fractionally crystalise out the tetra and leave any more soluble contaminants in the supernatant. I didn't do it in the end. I merely weighed the plastic pots and contents, making a note under them and will reweigh when I need to open another one up for use. This assumes the contents were indeed tetra as stated on the MSDS to start with.
    Murray
    The borate part of decahydrate and pentahydrate are identical. The difference is in the amount of water of crystallization. A saturated solution of either one at a given temperature contains exactly the same number of Na2B4O7 molecules. Once you have a saturated solution and have decanted the clear liquid, there is no point in trying to recrystallize the contents, because you are then back at the beginnibg. You still are not certain which of the crystals are pentahydrate and which are decahydrate. You still have to weigh the crystals to make any use of them, whereas the saturated liquid has a known content of the decahydrate per unit of volume and can be measured out with a graduated cylinder.

    The terms "pentahydrate" and "decahydrate" have no meaning in solution. However much water of crystallization was taken into a borax solution becomes part ot the solvent water. All you have in solution is Na2B4O7 molecules and H2O molecules. The molecule that entered as the pentahydrate carried 10 molecules of water with it. The molecule that entered as the pentahydrate carried 5 molecules of water with it. Now we have 2 molecules of Na2B4O7 floating around in 15 more molecules of water than we had before. There is no way we can tell which of the borate ions came in which which of the water molecules.
    Gadget Gainer

  4. #43
    Murray Kelly's Avatar
    Join Date
    Jan 2007
    Location
    Brisbane, QLD. Australia
    Shooter
    35mm RF
    Posts
    429
    Sorry - confusing my pentas, decas tetras etc. It's all greek to me.:rolleyes: Thinking metaborate. More greek.
    I dunno how it's done commercially but I'd presume if there's excess water the deca will form. Commercially it's cheaper to ship 3/4 ton of penta than 1 ton of deca and deliver the same amt. of borate. Therefore one might be led to suspect there is some contamination of deca with penta regularly since it's in the system.
    "You still have to weigh the crystals to make any use of them".
    Don't think you meant one could tell the difference by weighing the crystals. If you did I don't see how. Naturally one weighs crystals - how else?
    Is this one of Plato's Dialogues?
    Murray

  5. #44
    gainer's Avatar
    Join Date
    Sep 2002
    Posts
    3,726
    Images
    2
    In low huidity it shouldn't take much heat, but a lot of tumbling, to change the deca to penta. Whatever you start with, it's just as easy for me to put enough in a pot of water so that not all dissolves, decant the clear liquid, and note the temperature. As long as you keep it at that or higher temperature, your solution has a fixed % of the equivalent of sodium borate decahydrate. If you can't find the chart at www.borax.com I can send you a copy.

    Metaborate is another conundrum. It has two molecular weights which are identified as 4-mole and 8-mole, leading one to believe that these are states of hydration. However, one ghanges to the other in a closed container above a particular temperature and back again as the temperature reduces, obviously with no change of water content, so it is only of academic interest.
    Gadget Gainer

  6. #45
    gainer's Avatar
    Join Date
    Sep 2002
    Posts
    3,726
    Images
    2
    Quote Originally Posted by gainer View Post
    The molecule that entered as the pentahydrate carried 10 molecules of water with it. The molecule that entered as the pentahydrate carried 5 molecules of water with it. Now we have 2 molecules of Na2B4O7 floating around in 15 more molecules of water than we had before. There is no way we can tell which of the borate ions came in which which of the water molecules.
    I goofed and no one took me to task! What is the World coming to? The underlined word should, of course, have been "decahydrate".

    Now I have to worry that I don't expand the goof like the editorial correction to a newpaper article: "The reporter said that Officer McGurk, who made the arrest, was a defective on the police force. He should have said that Officer McGurk was a detective on the police farce."
    Gadget Gainer

  7. #46
    gainer's Avatar
    Join Date
    Sep 2002
    Posts
    3,726
    Images
    2
    Here is an interesting fact. 526 grams of borax decahydrate will dissolve in a liter of glycerol. I dissolved 120 grams in 500 ml, added 10 grams each of Phenidone and ascorbic acid, used 1+50 dilution of this solution to develop Arista Premium 400 for 16 minutes at 70F with excellent results. I think this might be a good stand developer. The pH of the working solution was about 8.5. The borax brings with it the water of crystallization, but at most that would amount to about 56 grams of water. If you have time for such frivolities, it's fun to play with. Even with heat it seems it will not all dissolve, but give it some time.
    Gadget Gainer

  8. #47
    gainer's Avatar
    Join Date
    Sep 2002
    Posts
    3,726
    Images
    2
    I was reading through a thread on Photo.net from 2004 dealing with accelerants for Gainer's developers. At the time, I had little interest in borax, but used carbonate or TEA. It turns out that the high solubility of borax in glycol is accompanied by formation of boronate esters that will be completely useless as bases. This is most likely to happen when heat is used to hasten solution. It explains why I thought my pH meter had gone bonkers. A working solution did a pretty good job of stand development at 45 minutes, 70 F.
    Gadget Gainer

  9. #48

    Join Date
    Nov 2004
    Posts
    1,180
    Why use 10g phenidone in 500 ml or 2g/100ml? Was it a typo or does this amount have a detectable different effect? In PC-TEA is only 0.25g/100ml.

  10. #49
    Murray Kelly's Avatar
    Join Date
    Jan 2007
    Location
    Brisbane, QLD. Australia
    Shooter
    35mm RF
    Posts
    429
    And presumably glycerol doesn't affect the buffering ability of borax like glycol?
    At 1:50 my scratchings on an envelope indicate there's 5g Borax - 0.4g Phenidone - 0.4g AA per litre (working). My maths has been known to err in the past but is there a decimal place wrong in there?
    Long ago I made up some PC-glycerol and it appears to keep just fine. I had no glycol.
    Murray

  11. #50
    gainer's Avatar
    Join Date
    Sep 2002
    Posts
    3,726
    Images
    2
    Quote Originally Posted by Alan Johnson View Post
    Why use 10g phenidone in 500 ml or 2g/100ml? Was it a typo or does this amount have a detectable different effect? In PC-TEA is only 0.25g/100ml.
    The pH of this working solution is considerably lower than that of the PC-TEA working solution. I added more Phenidone so I wouldn't have to wait so long. That is what prompted me to try stand development. 45 minutes was in fact somewhat too long, as there is some washing out of the highlight in the "mane" of my great grand daughter's hobby horse. You'll see it if I can get the photo transmitted.
    Attached Thumbnails Attached Thumbnails PCBGLYCOL50 STAND0001.jpg  
    Last edited by gainer; 07-07-2009 at 10:05 AM. Click to view previous post history. Reason: misspelling
    Gadget Gainer



 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin