This section is from the "Elixirs And Flavoring Extracts. Their History, Formulae, & Methods of Preparation" book, by John Uri Lloyd. Also available from Amazon: Elixirs and flavoring extracts,: Their history, formulae, and methods of preparation;
Elixir of pyrophosphate of iron, 8 fluidounces.
Elixir of pepsin, 8 fluidounces.
Mix them together, and, if not neutral or of slightly alkaline reaction, cautiously add ammonia water until it will change blue litmus paper to red.
Each fluidrachm (teaspoonful) of the finished elixir contains one grain each of pyrophosphate of iron and such a modification of pepsin as can exist under the conditions necessary to form the elixir.