I have refrained from posting in this thread until now. I feel that I have to clarify my position as well.
Originally Posted by Kirk Keyes
Kirk not only has his chemistry straight, he has also stated in this quoted post my own thoughts on this matter.
The most common impurities are halide salts and insoluable colloidal salts. Patrick has alluded to the latter in the past saying that some of his Borax solutions are cloudy and the cloudy suspension cannot be filtered out.
This whole thing may be summarized by saying that Patrick is trying to prove his point, that he can compound usable developers. That is conceded, but due to lack of full checks, we don't know how they compare in detail to off the shelf developers. In fact, in some test comparisons shown in other threads, I (and others) have given the tip of the hat to the commercial (albeit modified) developer.
I am not a borax chemist, but in private notes, I have exchanged similar, but less specific informaiton with Patrick discoraging him from the view that an ester or other type of compound is being formed. This was obvious to me, but the details were unclear and I had no text references for help. I thank Kirk for giving us the complete story on this.
interesting! up until a couple of months ago when another member very generously gave me about twenty pounds of old photo chems, I had always used 20 Mule Team Borax from the grocery store in my home brew ....
That stash of chemistry included a one pound jar of Kodak Borax - which I have been using ever since.
I too noticed the cloudiness with the grocery store Borax...and now that it is mentioned, I have not noticed it with the Kodak Borax.
Very interesting. I think I'll leave the 20 Mule team in the laundry room from now on.
I'm no "borax chemist" myself, but as an analytical chemist, you can be exposed to a lot of different analytical techniques that are sometimes forgotten in the modern world of chemistry. Nowadays, to measure boron content, an ICP (Inductively Coupled Plasma atomic absorbtion spectrophotometer) or even an ICP-MS (one with a mass selective spectrometer attached) would be used. 50 to 20 years ago, an AA (atomic absorption spectrophotometer) would have been used. The titration with glycerine was used from about 100 years ago until labs could afford AA's in the 50s and 60s.
In point of fact, the borax that I used in these later experimental developers was the photo grade from Photographers' Formulary. My main interest at this time has shifted from borax to glycerol. I had been using it as a solvent at time when I had no propylene glycol at hand. At room temperature, it seems to serve as well except for the higher viscosity for the preparation of higly concentrated stocks like PC-Glycol. It occurred to me that the high solubility of borax in gylcerol would allow a single solution concentrate of Phenidone, ascorbic acid and borax in glycerol. I am pretty sure that in the process of heating the mixture for faster solution to between 250 and 300 F I did form the glycerol borate. The pH of the working solution was considerably lower than I would have gotten from a water only solution of the same small amounts of Phenidone, ascorbic acid and borax.
The 1+25 working solution of the glycerol stock seems to have buffering properties, as the addition of fairly large amounts of borax produces little change of pH, which stays below that of a 0.1N borax solution. The resulting developer is quite good, but slow.
There is also a glycerol sulfate, which gave me the idea test the solubility of Metol in glycerol. I have dissolved, with heating, 10 grams each of Metol and ascorbic acid in 180 ml of drugstore glycerol, which is nearly anhydrous and of medicinal quality.
The very first thing I did was to prepare a nearly saturated solution of borax in very hot water. After cooling, most of the borax had settled out, leaving only about 47 grams/liter in solution along with most of the soluble and colloidally suspended impurities. Decanting the solution thus removed most of the soluble impurities. There is no point in trying to filter out any impurities, be they truly dissolved or colloidally suspended, if they can be decanted at the cost of only a few percent of the original amount of borax. Furthermore, even the best grade of borax is likely to be a mixture of pentahydrate and decahydrate, so in any case where an accurate assay of Na2B4O7 is required, the standard procedure is to prepare a saturated solution. This solution, if kept at a temperature above that of its formation, will have a known borax content expressed as weight percent of the decahydrate. Thus, a saturated solution formed at 20 C will contain 4.71% sodium tetraborate decahydrate, or 47.1 grams per liter.
Originally Posted by Photo Engineer
I think you will see if you look at my developers, that I have for many years spent most of my effort designing sulfite-free developers. The major thing I have against sulfite is cost and local avilability. It is often the most expensive component, and among the hardest to get. Anyway, it's part of my fun to see what I can do with what I can get in the middle of Wild and Wonderful West Virginia.
It's easy to get it at a photo store. At least the photo shops around here.
Originally Posted by gainer
Pat - do you make corrections for when your borax solution is not at exactly 20C?
Originally Posted by gainer
I hope you have an accurate and precise thermometer. If you are off by 1 degree, you will get a 4.52% solution if you are low, and 4.94% if you are high. That's an error of 5% for just a change of 1 degree Celcius.
I have to say I think just wieghing your borax is a lot simpler and more expedient. And more accurate.
And that's assuming you have time to let your borax solution sit around so that it's truely saturated - not undersaturated and not over saturated.
Kirk, if the saturated solution has been decanted from the undissolved sediment at 20 C, it will contain 47.1 grams of borax per kilogram of solution at any higher temperature. For practical purposes, even if you measure by volume at a higher temperature, the change due to expansion of the liquid will not throw you off as much as the possible variation in weight per mol of Na2B4O7 due uncertainty of the average amount of water of crystallization. How do you ascertain that number? Every time you open the container, the contents are subjected to possible changes in humidity. The 5 pounds I bought from the Formulary has huge lumps, small lumps and powder, which indicates changes in water of crystallization have occurred, but from what to what?
If you are going to be a stickler for precise measurement of borax, your best bet is a saturated solution. I think the best way to make it is to start from saturation at a higher temperature and to let it cool to the desired temperature. If it takes a while, so be it. as the saying goes, "Think ahead."
I did not continue my formal study of chemical engineering, but changed to aeronautical. I am an engineer by nature, as anyone who knew me during my years at NACA-NASA would testify. As one of our instructors in engineering was fond of saying, "Engineers can do anything."
I think that phrase should be "Engineers will do anything". This does not give it the stamp of approval however, nor does it ensure that their chemistry is correct as Kirk has pointed out.
Imagine building the port on a Mercury capsule (an example given by Patrick in another thread), and it has a 5% variation in size. One would leak (too small), one would crack (too big), and one would be just right! I think that this analogy is apt although the results would be far less draconian in photography. If you had a 5% variation in alkali content, your pictures might be usable but you might wonder why your contrast or sharpness varied as much as it did.
And what makes you think I might have had a 5% variation in alkali content? I told you I used the photo grade borax I got from PF. Is it that bad? Even the stuff I get by processing the household variety is better than 5%.
By the time the Mercury became a project, I had been assigned to do basic human factors research, and to design star charts to be used as backup reentry alignment. What did my education in AE have to do with that? It made me ask questions and search for answers. I no longer have the technical library I could access at Langley Research Center.
Kirk, there is no photo shop within 100 miles of here in any direction. My formulas are not only for my use, but have been used in remote locations in New Zealand. (Jacko Twist, where are you?)