A bought a gallon awhile back and it is indeed 99% pure. You can tell by the lack of smell. As far as PF is concerned, I won't buy from them. They are expensive and I wonder about the actual purity of the chemicals they sell. As I said the Chemistry Store's TEa is intended for topical use in lotions and so cannot contain DEA or MEA. The liquid is viscous, water white and has the correct Sp Gr for TEA 99%. I used it to make up an ascorbic acid developer (Dimezone, ascorbic acid, TEA, propyelene glycol) and it worked fine. They also sell several other chemicals that are of use in photography such as hypo. sodium sulfite, sodium carbonate, propylene glycol, Triton X-100, etc. They also sell PET bottles. Their prices are more reasonable than most other suppliers.
Retail prices are set at their levels for all sorts of reasons. Even here in Australia, where nearly everything costs more, 5L of 99% TEA cost me $20 (Aust dollars, at the time less than US dollars). I had to bring my own container. The vendor was a firm specializing in specialized lubricants for industry.
Originally Posted by albada
Boric acid B(OH)3 and borates are a bit of a problem since boron likes to make B-O-B bonds. So the actual structures may be more complicated than the stochiometric formulas would indicate. If boron behaved normally you wound expect something similar to the following series of compounds which phosphorous exhibits; PO(OH)3, NaO2(OH)2, Na2O3POH, Na3O4P. As one goes from phosphoric acid to sodium dihydrogen phosphate to disodium hydrogen phosphate to trisodium phosphate the pH rises so that the trisodium salt is a very strong alkali almost as strong as sodium hydroxide. For borates with complex structures you simply cannot base alkalinity on the number of boron atoms in the molecule.
In the titration of boric acid you would expect to see a three step curve as each of the three OH groups is neutralized. However what is seen is a somewhat smooth rise in pH as NaOH is added. To see the steps clearly the simple sugar mannitol is added to the solution to break any B-O-B bonds. The boric acid then behaves more like a normal acid and exhibits a three stepped curve like phosphoric acid.
To add to what Jerry said, buffer capacity can be looked at as the total number of moles of alkali present in a solution. Thus, water has zero buffer capacity and lets say that it is at pH 7 (protected from CO2 in the air of course). So, if we add a pH 7 buffer, then the buffer capacity rises but the pH stays constant.
Addition of dilute acid or base to plain DW will change the pH rapidly, but adding dilute acid or base to the buffered DW will cause a slower change if any takes place at all.
Jerry and john_s:
You've convinced me! I'll be buying some 99% TEA from ChemistryStore this evening, and I'll adjust the developer formula.
And thanks for the postings about the interesting behavior of borates and buffering. The more I learn about chemistry, the more I appreciate how many things need to be determined (or at least verified) by experimentation.
Here's a modification of the TEA-based concentrate versus XTOL:
Notice the slight elbow at 1.5 on the X-axis. I've seen that before, and I suspect it's due to rotating developer in the tank developing the outside of the test-strip more than the center. So I'll be making baffles to stop movement of liquid and run more strips. As Michael R pointed out, we're down to such slight differences that a micro-densitometer is needed, and I don't want to distort things with uneven liquid-flow.
Here are crops of the latest TEA-type concentrate:
Xtol:Attachment 54617, TEA con:Attachment 54618
Xtol:Attachment 54619, TEA con:Attachment 54620
The densities aren't quite the same due to hassling with exposure on the scanner, but these should give you a good idea of the grain.
Your TEA concentrate looks sharper and less grainy.
Thanks for the encouragement. I guess the next step is to mix it as a concentrate and make sure it doesn't crystallize. And then comes the boring tests that must be done.
Originally Posted by Photo Engineer
It occurred to me that since the crystallized stuff (with the high concentration ratio) has cream-like viscosity, it might be dispensed out of a squeeze-tube like lotion. But one would get controlled amounts of it by dispensing one of more strips onto the left portion of a ruler. Then one would use the ruler as a stirring-paddle when mixing the developer. This scheme has the advantages of very high concentration and ease of use, but I wonder if the cream will be subject to separation. In the bottle, due to excess PG, the top third is liquid and the bottom two thirds is cream. I don't know if the cream alone would separate into more liquid. Oh great, another idea to explore...
Jerry and john_s: The deed is done! I just gave $116.39 to the ChemistryStore.com for several chemicals. One third of that total is cross-country shipping.
Just curious: Jerry mentioned that (poly)borates react with mannitol which breaks up polyborates. Upon further investigation this reaction is not specific to mannitol, in fact many polyalcohols do this. Is there a chance that PG also does this? Could this mean that Mark's formulation already takes advantage of this effect?
I only mentioned mannitol because it is what is typically used when titrating boric acid. Boric acid combines with glycerol which is also used for the purpose mentioned. The only restriction that I know of is that the OH groups must be on adjacent carbon atoms. Of course this is always true with glycols.
The carbon backbone can be either aliphatic or aromatic an example of the latter is catechol. In the case of catchol the developing capability is effectively destroyed by the formation of the borate ester. The only change in a borate buffer system would be the pH with the addition of the glycol.
Those of you who run test-strips of neg's might be interested in my latest test-setup:
The strip is held down with hobby-magnets, with corresponding magnets under the bottom. The big white thing is my latest addition: It's a baffle to prevent developer from rotating in the tank and developing the outside more than the centre. It's a PVC extrusion which happened to fit well, but anything that blocks rotation of fluid should work. I glued shims on the bottom so it won't touch the neg. The neg you see is in fixer, and was developed in XTOL. Here's the graph of that neg:
My goal is to get corporate-quality test-results on a home-budget. If somebody has a better idea for developing strips uniformly, I'm all ears.