The US patent literature is full of wondrous inventions and its easy access by computer-machine over the internets is a real boon to historians and hacks like myself.  In the course of my studies into 19th century gold metallurgy, I stumbled across US 7,521, issued July 22, 1850. This patent was issued to Albert N. Henderson of Buffalo, NY.  Mr. Henderson’s invention is entitled IMPROVEMENT IN THE APPLICATION OF ELECTRO-CHEMICAL PRINTING IN COLORS FOR TAKING AYES AND NOES. 

Henderson describes an apparatus for taking the ayes and noes by galvanic electricity and specifically proposed it for use in legislative assemblies. The concept was that at each desk in the assembly would be two keys (switches, as we now call them) for voting either Aye of No. The member would press one of the keys when called to vote, with the result of an electric current passing to a central apparatus with specially treated paper pressed between electrodes. The action of the current in the damp treated paper would be that a vote would be registered as a mark on the paper, recording the vote of the member.  In the end, the only gold connection in the patent related to gold electrodes as a preferred embodiment.

Claim 1.  This patent claims a mode of imprinting words, letters, & figures, etc, upon paper or other fibrous substances between two surfaces of a metal which is not acted upon by the substances employed, on one of which the letters or figures are raised by passing a current of galvanic electricity through the prepared material, substantially as above described.

Claim 2. Passing the electric current between metallic surfaces, as above described, through damp paper otherwise unprepared, and afterward applying a chemical solution, by which the effect of the electricity becomes visible whenever it has passed through the paper, for the purposes above described- telegraphing, etc.

Substances which may be used as part of the solution for the preparation of the paper- Copper sulfate (gives black impression), Potassium cyanide which may be acidified with H2SO4 or HNO3 (!!) to impart a green color with the galvanic current.  A strong solution of KCN with Ag chloride gives a green impression. All above leave white paper until acted upon by electricity.  A weak soln of potassium ferrocyanide (prussiate of potassia) colors the paper slightly and leaves a deep blue impression by the electricity. Henderson prefers to use electrodes of gold or platinum.

This invention has a kind of steampunk aspect that I find very appealing. On the other hand, it is hard to know what knowledge the inventor had with regard to the hazards of KCN or acidified solutions thereof. The patent is silent with regard to the chemical safety questions arising from the use of KCN treated paper.

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