This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
Iron, in the form of fine wire and cut into small pieoes, fifteen parts; hydrochloric acid, eighty-six parts; nitric acid, distilled water, each, a sufficient quantity. Put the iron wire into a flask capable of holding double the volume of the intended product, pour upon it fifty-four (54) parts of hydrochloric acid previously diluted with twenty-five (25) parts of water, and let the mixture stand until effervescence ceases; then heat it to the boiling point, filter through paper, and, having rinsed the flask and iron wire with a little boiling distilled water, pass the rinsings through the filter. To the filtered liquid add twenty-seven (27) parts of hydrochloric acid, and pour the mixture slowly and gradually in a stream, into eight (8) parts of nitric acid, contained in a capacious porcelain vessel. After effervescence ceases, apply heat, by means of a sand-bath, until the liquid is free from nitrous odor; then test a small portion with freshly prepared test solution of ferricyanide of potassium - one part of ferricyanide of potassium in ten (10) parts of distilled water. Should this reagent produce a blue color, add a little more nitric acid and evaporate off the excess. Then add the remaining five (5) parts of hydrochloric acid and enough distilled water to make the whole weigh sixty (60) parts, and set this aside, covered with glass, until it forms a solid, crystalline mass. Lastly, break it into pieces, and keep the fragments in a glass-stoppered bottle, protected from light. Orange-yellow, crystalline pieces, very deliquescent, odorless, or having a faint odor of hydrochloric acid, a strongly styptic taste and an acid reaction. Freely and wholly soluble in water, alcohol or ether. Chloride of iron is dissolved for immediate use, best in some carbonated water drawn from the fountain, which is then airless; the solution is then filtered and quickly poured into the fountain, after the atmospheric air has been removed therefrom as directed.