or
owners of the papyrus were chiefly interested in making ornamental
jewelry and not in practical metals such as bronze and steel. At any
rate the recipes for alloys in this papyrus are the earliest detailed
quantitative directions for alloy manufacture that we have knowledge
of. Other ancient writers such as Pliny and Dioscorides who touch upon
technical subjects are singularly lacking in details, indicating their
lack of direct knowledge, but the papyrus here considered is certainly
a direct laboratory document and hence its importance for the history
of chemistry.
Next
in importance to the making of the alloys themselves come the recipes
that deal with refining, cleaning, coloring, and otherwise treating
metals. The second recipe in the papyrus is an example of the
purification of metals by adding reducing agents to the molten metals,
pitch and oils being used for this purpose. Another method of
purification that was evidently in use in ancient times was the
addition of various chemical salts to fused metals and alloys to serve
as fluxes and solvents for the impurities. Alum, iron sulfate, crude
soda ash, and common salt were most commonly employed for this purpose.
Several recipes are given for cleaning and polishing the surface of
cold metals. The softening and hardening of metals was also quite
well-known then as several of the recipes show, and this is borne out
by the fact that the hardening of steel bv tempering was a familar
operation in Roman times. A curious sidelight on the impurity of the
crude metals then employed is shown by the fact that recipes for
hardening lead are in reality only those for removing excessive
impurities, an indication that the crude metal was mixed with
quantities of oxides.
The
coloring of metals superficially was evidently widely practised.
Mercury was applied to alloys and base metals to give a silvery
appearance as well as being incorporated in the alloys themselves. A
curious method of gilding with gold is given in Recipe No. 38 in which
a mixture of powdered gold and lead are fastened upon an object with
the subsequent burning off of the base metal. The use of gold amalgam
in gilding silver is also fully explained in No. 57. Besides using
metals for coloring metallic surfaces they also employed various
colored varnishes and dyes as several of the recipes of the papyrus
indicate. Recipe No. 89 is especially interesting from the chemical
point of view as being evidently a preparation of a solution of
sulfides of calcium, the original lime-sulfur mixture. This is the only
actual preparation of a chemical salt listed in the collection.
Probably this was used to color the surfaces of metals also.
The
crude methods of testing gold and silver for purity employed in those
times are well described in Recipes No. 43 and 44. The discoloration
of the metals by the formation of metallic oxides was depended upon to
indicate fraud. No doubt this was sufficiently accurate to indicate
