Crystalline Ferric Ammonium Citrate -another way to simple cyanotype?

[PGum]

This was a side project of mine in an attempt to see if simple cyanotype (simple FAC) could be made without the additional byproduct salt of ammonium nitrate. I thought that there may be a way to replace the oxalate in ferric ammonium oxalate (FAO) with citrate by precipitation. I used calcium carbonate.

I first added citric acid to the FAO. Then added in calcium carbonate with continuous stirring for about 20 minutes. Once all was done, I tested for free oxalate with calcium acetate (calcium chloride does not work), and free calcium with ammonium oxalate. If either produced a precipitation, I added a bit more of the opposite salt. I left it overnight and checked again. Once free of either, I left it to decant for a day and drew off the supernatant.

I left the mixture to dry to the point of a tarry residue and scrapped that up with a rod and placed it into a small glass vial. I placed this in the fridge for a week and noticed what looked like a small opaque mass, not being sure if this was crystals. I left it in the fridge for one more week, and checked again -no change!. I then removed the vial and left it at room temperature for a few days. I checked it again and there was significant crystal growth -the masses growing like cauliflower, which eventually filled the vial. It seems that the warm up accelerated the growth. Upon removing some crystals, adding a bit of water and letting it dry, the crystals did not reform on drying on a glass slide at RT, RH 40%, forming a glassy film. It seems that very specific conditions are needed to get crystallization.


Here are the amounts I used:

10 ml distilled water
2 g Ferric Ammonium Oxalate (FAO)
1.5 g Citric Acid
2.25 g Calcium Carbonate


I proceeded to make a test print. The dmax was less than simple cyanotype (Ware). Then I added a small amount of ammonium nitrate, which I had to make, as I don't see it available to buy, the dmax improved. It seems that the ammonium nitrate in the simple cyanotype is making a contribution. I have also used this approach to make ferric ammonium lactate and it worked quite well, but did not attempt crystallizing the FAL.

Peter Friedrichsen

close-up

 

[nmp]

This is cool, Peter. Thanks for sharing. I wonder if the original paper that characterized FAC with x-ray diffraction prepared theirs the same way. (EDIT: No, they actually made it from feN/CA/NH3 and then precipitated with ethanol - from Cyanomicon.)

Regarding ammonium nitrate, Mike Ware describes one of its roles this way:

(From Cyanomicon, p207)

It is also possible that the presence of ammonium nitrate in the
dried sensitized layer, which is consequently somewhat
hygroscopic, will assist print-out of the image by maintaining
humidity within the paper, (as it is observed to do in the Malde-
Ware print-out Pt/Pd process).

May be that's what is going on with the greater Dmax seen when you added external amount.


:Niranjan.

 

[PGum]

This is cool, Peter. Thanks for sharing. I wonder if the original paper that characterized FAC with x-ray diffraction prepared theirs the same way. (EDIT: No, they actually made it from feN/CA/NH3 and then precipitated with ethanol - from Cyanomicon.)

Regarding ammonium nitrate, Mike Ware describes one of its roles this way:

(From Cyanomicon, p207)

It is also possible that the presence of ammonium nitrate in the
dried sensitized layer, which is consequently somewhat
hygroscopic, will assist print-out of the image by maintaining
humidity within the paper, (as it is observed to do in the Malde-
Ware print-out Pt/Pd process).

May be that's what is going on with the greater Dmax seen when you added external amount.


:Niranjan.

Niranjan,

I am also curious to see if the AN is making a contribution to the lengthened tonal scale and reduced grain. I speculate that it may be playing a part here too. In the coming weeks I will run additional tests with and without AN.

As far as using the technique to make FAL, I found it had more iron than one would expect stoichiometrically, as we speculated with Mike Ware’s input. It still made a print however. More ammonia and citrate seemed to improve it.

 

[nmp]

I am also curious to see if the AN is making a contribution to the lengthened tonal scale and reduced grain. I speculate that it may be playing a part here too. In the coming weeks I will run additional tests with and without AN.

Generally my experience with various POP processes (salt, cupro, and cyano) is that a certain amount of moisture helps all of these - Dmax, tonal scale and grain. That might as well be the case here - barring any chemical interactions due to nitrate that might also interfere in the process, fortuitously or otherwise..

As far as using the technique to make FAL, I found it had more iron than one would expect stoichiometrically, as we speculated with Mike Ware’s input. It still made a print however. More ammonia and citrate seemed to improve it.

If I remember correctly the FAL process is to prepare the mix lactic and ammonium first and then add freshly prepared ferric hydroxide to it. So here you combined citric acid to ammonium carbonate and then added ferric hydroxide, right?

Speaking of FAL, by the way, I did do a considerable amount of work trying to make it using the Simple process. I hit a snag and then got side-tracked by many other things. The snag was that on addition of ammonia (by way of ammonium bicarbonate,) the solution gels above a certain amount (looked like a lovely green mayonnaise.) Never did do any printing though. Then I ran out of lactic acid and the project went by the wayside. Should have shared the results then. Now I don't even know where my notes are... May be one these days I will revive the project.

:Niranjan.

 

[PGum]

Niranjan,

Sometime I may revive that thread of making FAL using this approach. My approach for notes is that I have dedicated notebooks serialized by start and end date, writing those two dates on the spine, ”mostly” avoiding the temptation to jot things down outside of those. I don’t often get around to writing a table of contents however.

 

[nmp]

Niranjan,

Sometime I may revive that thread of making FAL using this approach. My approach for notes is that I have dedicated notebooks serialized by start and end date, writing those two dates on the spine, ”mostly” avoiding the temptation to jot things down outside of those. I don’t often get around to writing a table of contents however.

That's how we did it in the lab back in the day. And then get signed by a witness on every page in case any of that stuff was patentable. I started using loose sheets because they are easier to stick pictures and test prints to. I am generally good at writing notes but it's when I "organize" and file them in some folder, then forget which one, I get into trouble.... Now I will have to look at every folder and as Murphy's law would dictate, it will be in the last folder I would look in.

:Niranjan.