The Pnictogen Wing

plate 39, opaque & polarizing objects, and plate 42, rocks, from the micrographic dictionary: a guide to the examination and investigation of the structure and nature of microscopic objects, 1883 (biodiversity heritage library)

honestly I wouldn't be surprised if someone hadn't tried this, back in the early days of photographic invention, when an enormous host of photochemical reactions were tried for making photographic negatives and prints. there's "anthotype", for example, a method in which photochemical bleaching of anthocyanin pigments from flowers was used to create an image.

a more durable method of photographic chemistry is the "cyanotype" or "blueprint" method, which takes advantage of the photochemical reduction of iron(3) in certain complexes, like tris(oxalato)ferrate(3) or Fe(C₂O₄)₃^≡, and subsequent reaction of iron(2) with hexacyanoferrate(3) or "ferricyanide", Fe(CN)₆^≡, to yield the deep blue pigment known variously as "Prussian blue" or "Turnbull's blue". one can purchase cyanotype papers commercially, "develop" them and then wash out the residual soluble iron compounds with water to get a permanent "blueprint". it's a very striking method and simple to replicate in the laboratory...and it's prompted us to wonder about the possibility of a related method, using cobalt compounds.

like iron, cobalt tends to prefer to exist, in aqueous solutions, as divalent and tervalent compounds—Co(2) and Co(3). and like iron(3), cobalt(3) forms a tris(oxalato) complex. potassium tris(oxalato)cobaltate(3), K₃Co(C₂O₄)₃, is readily prepared as a deep green crystalline compound by dissolving cobaltous oxalate in an excess of potassium oxalate solution and oxidizing the Co(2) to Co(3) with hydrogen peroxide (or prolonged exposure to oxygen.) and like the iron analogue, tris(oxalato)cobaltate(3) is subject to photochemical reduction upon exposure to sunlight.

this suggests to us a possible "cobaltotype" method that may directly yield a black print rather than a blue one: prepare a photographic paper that contains a tris(oxalato)cobaltate(3) salt (perhaps along with some photosensitizing dyestuff) and expose it to light, whence the Co(3) salt will decompose and deposit insoluble cobaltous oxalate, CoC₂O₄, which is pink. wash away the remaining soluble salts and then treat the paper with an alkaline oxidizing solution—common sodium hypochlorite bleach may do the job—and the pink CoC₂O₄ will be oxidized to insoluble black Co(3)-containing oxides, like Co₃O₄. the end result should be a black-on-white photographic print...if our surmise is correct about the chemistry involved. we would like to test the method, though first it will require cleaning up our workroom and preparing a number of cobalt salts. my daughter Alyx Woodward is quite keen on such a project.

~Mona Drafter of Pnictogen

awoo

🐉 I am smol derg but I can awoo. awoooooo! :} :} :} ~kel

Am woof. When I see other's go awoo, I just want to awooooo! too 🐺💖

awoo

🐉 I am smol derg but I can awoo. awoooooo! :} :} :} ~kel