[Chemistry of cosmetics in antiquity]

Several texts, statues and paintings denote the importance of make up and eye medicines since the earliest periods of Egyptian history. We have investigated cosmetic powders that were preserved in original alabaster and reed containers. Quantitative crystallographic and chemical analysis of the mineral and organic components revealed surprising facts. In addition to the well known galena PbS and cerussite PbCO3, two unexpected constituents have been identified: laurionite PbOHCl and phosgenite Pb2 (CO3) Cl2, which are rare halide minerals found in lead slag only in certain places where the sea water has weathered lead debris left over from silver mining operations in Antiquity. Alteration of natural lead minerals is also unlikely, given the excellent state of conservation of the reed vessels. This evidence indicates that laurionite and phosgenite were synthesised artificially. Support for this statement comes from recipes of medicinal products to be "used in ophthalmology" reported by Greco-Roman authors such as Dioscorides and Pline (1st Century B.C.): silver foam PbO is crushed and mixed with rock salt and sometimes with natron (Na2CO3). The reaction seems to be straightforward. However, our experiments in the laboratory have shown a major difficulty, arising from the concomitant production of alkali, which raises the pH and leads to different products. It follows that the Egyptians very early mastered this kind of chemical synthesis and technology, a fact of great importance in the History of Sciences. Fire-based technology had been mastered to manufacture Egyptian Blue pigments since the third millennium B.C. The present results now suggest that wet chemistry was already known 4000 years ago. This key finding provides a new insight into the chemical technology of far greater antiquity than has previously been believed. Yet, an important question remains relative to the ultimate motivation for these technological developments. If the Egyptians initially only aimed at different nuances of grey, they could use cerussite, an easily accessible mineral, crushed and mixed with galena. Thus, one should seek other motivations; we shall propose to consider a religious-ritual context, ultimately linked to a pharmaceutical aspect.