The following is an excert from the book ‘Pathfinders: the Golden Age of Arabic Science’ by Jim Al-Khalili, p62-65.
A great example of applied chemistry was the manufacture of soap, which by the thirteenth century had become industrialized: the town of Fez in Spain had some twenty-seven soap-makers, while cities like Nablus, Damascus and Aleppo became famous for the quality of their soaps. I am referring of course only to solid soap bars and not suggesting that the Arabs invented soap itself. But it is the industrialization of the manufacture of soap bars that is new.
The chemists’ understanding of the properties of alkalis and other chemicals gave the glass-making industry a lift, too. They discovered that the colour of glass could be changed using new chemicals like manganese and newly discovered metal oxides. With their industrial furnaces, some several storeys high, they were able to manufacture coloured glass in huge quantities.
What all the medieval Arabic texts on chemistry have in common is great attention to detail based on careful experimentation. The techniques that were developed drove a thriving and successful industry, but we also see in the work of Jabir the beginings of chemistry as an empirical science motivated by a desire to understand how the world is made up.
The Greeks’ belief in the four fundamental elements of earth, air, fire and water was a purely philosophical idea with little practical value. Chemists in the Islamic Empire changed that, for they were the first to use experimental observations to classify the substances they knew.
One of al-Razi’s greatest achievements was his classification scheme. Around the year 900 he classified all substances into four groups: animal, vegetable, mineral, and derivatives of these three. His minerals were further tabulated into six categories according to their chemical properties rather than superficial appearance, the same guiding principle that lies behind the modern periodic table. They were: spirits (such as quicksilver and sulfur), metals, stones, atriments, boraces and salts. Each group had a chemical property profoundly different from all the others: spirits were flammable, metals were shiny and malleable, salts dissolved in water, and so on. While these classifications are not how we organise chemicals today, the point is that, for the first time, al-Razi was grouping substances on the basis of experimental observations, not philosophical musings.