بررسی خواص آماده سازی مواد شیمیایی باستانی: رنگدانه ها و داروها در قرون وسطی اسپانیای اسلامی

The analysis of the contents of an Islamic glazed ceramic pot found in Zaragoza (Spain) revealed an ancient ‘chemical’ preparation (11th century AD). The use of several analytical techniques (optical microscopy, scanning electron microscopy with X-ray energy-dispersive spectrometry and X-ray diffraction, and pyrolysis-gas chromatography/mass spectrometry) enabled us to identify mineral, organic and vegetal components: orpiment, a fig, and some grape seeds, together with a small amount of gypsum. The purpose of this mixture may have been for colouring because orpiment, the yellow sulphide of arsenic, has been used as pigment in painted decorations and manuscripts since ancient times. Nevertheless, since “yellow arsenic” was also one of the most common remedies in Arabic pharmacology and medicine, the components we identified may have been part of a medical treatment. Moreover, knowledge of the chemical composition of the contents of this pot provides a means of establishing the best way to conserve them.

The characterization of archaeological materials is very valuable in terms of what it reveals about the artistic and manufacturing techniques of the past. An in-depth analytical study of ancient products can reveal information on how advanced technologically ancient societies were, and also on their diet, trade, rituals, and everyday activities (Goffer, 2007). Knowing the composition of archaeological findings also enables us to assess the state of conservation and ongoing degradation processes, to set up exhibition and storage conditions, and to plan the right conservation treatments. This paper reports the results of an investigation on the original contents recovered from a small glazed pot. The object was found during archaeological excavations from the ancient wall of Zaragoza (Fig. 1). This city wall was constructed in Roman times. For centuries some buildings were attached to the wall and part of these houses have remained buried in the sediments at the foot of the wall. The small glazed pot (Fig. 2) was found in these sediments, in the inner side of the wall, together with ceramics —almagra (red slip) and manganese-decorated pottery— and a large number of glass fragments, that suggest they belonged to an Islamic context, dating to the 11th century AD or Taifa period (Carrasco et al., 2009). The ceramic pot is 6.5 cm high, with a maximum diameter of 6.6 cm, completely glazed both inside and out, is yellow-honey in colour, and decorated with brown-black stripes. This type of decoration was common in Islamic ceramics of Taifa period, it was produced on an alkali-high lead glaze (around 3% K2O + Na2O and 45–48% PbO) and painted with manganese pigments (Pérez-Arantegui and Castillo, 2002); the pottery was made with calcareous clays, producing a cream body. Unlike in most other finds, part of the contents was blocking the mouth of the pot and it was not empty. This enabled us to study and analyze the complex contents. The main objective of this study was to understand the composition, but also the purpose of the products contained in the ceramic pot, using samples as small as possible. The knowledge we acquired of this composition means that sustainable methods can be found in order to conserve the pot and its contents. A multi-analytical approach, based on the use of complementary techniques, was carried out on the material collected from the pot in order to identify the materials in the object. Optical microscopy (OM) and scanning electron microscopy with an energy-dispersive X-ray spectrometer (SEM-EDX), together with X-ray diffraction (XRD), were all used to highlight the composition and the nature of the inorganic components and the presence of vegetal components. Pyrolysis-gas chromatography coupled with mass spectrometry (Py-GC/MS) was complementary used to reveal the presence and the composition of other organic substances.

The analysis of the contents of an Islamic glazed ceramic pot highlighted the ingredients of an ancient ‘chemical’ preparation. Mineral, organic and vegetal components were identified thanks to the use of several analytical techniques in few micro-samples. In the moment of the finding, the small pot contained a fig, three grape or raisin seeds, a significant quantity of orpiment (6.5–7 g) and a small amount of gypsum. The purpose of this mixture may have been as a colouring agent: a pigment with a possible yellow, orange or “golden” tint. Nevertheless, due to the lack of knowledge available on medieval compounded drugs, the mixture may have been used as part of a preparation of a medical treatment. Orpiment and figs were well-known components of remedies, as “simples”, thus the use of both ingredients in conjunction may have been to modify their result or even to prevent the poisonous effects of the arsenic. Knowledge of the composition of the contents will also help in choosing a suitable conservation treatment of the pot and its contents. The natural perishability of the fig and the seeds, and the chemical reactivity of the orpiment require special conservation procedures. On the one hand, the organics must be preserved and on the other, the orpiment requires an inert environment for. In addition, due to the poisonous nature of the As2S3, the exhibition and storage conditions need to be carefully selected.