Various, Notes and Queries, Number 173, February 19…
“ Shadbolt, I may observe, to one who is in the habit of iodizing paper, a considerable amount of the passage relating to cyanide of potassa could not be misunderstood; the nitrate of silver being added to the iodide of potassa, forms at once a precipitate which it is required to take up. The old double iodide says, add iodide of potassa till it does so, and it will do so; but the cyanide of potassa does it much better, and the cyanogen is lost as the paper dries, otherwise it would take no image at all. ”
