Technikatörténeti szemle 10. (1978)

A MÉRÉS ÉS A MÉRTÉKEK AZ EMBER MŰVELŐDÉSÉBEN című konferencián Budapesten, 1976. április 27–30-án elhangzott előadások II. - Szabadváry F.: Tömegmegmaradás elve; mérés és számolás a kémiában

role not only in practical life but also in religion, as demonstrated by numerous surviving paintings. The balance was always present in the laboratory, and the oldest branch of chemistry, namely analytical chemistry cannot exist without a balance. Analytical chemistry was called into existence by the need to assay gold. While the quality of everyday goods could be determined by use or by organs of sense, the quality of gold could not be decided by its taste, touch, shine or tinkle, exact methods were necessary for this purpose. Archimedes set up his thesis in connection with the quality control of gold, and necessarily used a balance for this purpose. The assay method of noble metals developed in antiquity and used up to the present time, namely cupellation, also requires a balance. It involves melting with lead and driving off the lead, followed by weighing the residual gold corn (termed gold king in German assay terminology). This gold assay method was first regulated in detail in Hungary, by the decree of King Karoly I issued in 1342. One year later, the decree issued by Philippe VI, King of France, described the method with almost standard-like accuracy, specifying for instance that the assayer should not use the balance in a cold and draughty room, and should avoid to influence the balance plate by his breath. Assaying balances were fairly sensitive, we know that their accuracy was in the order of centigrams. The balance is of fundamental importance in analytical chemistry up to the present day. Although a large variety of other instruments are now at disposal of the chemist, their signals must somehow be reduced to mass, and this is where the balance comes in, either in the determination itself or in calibration. In chemical theories, as we have seen, measurement plays a role since the age of medical chemistry. It was not the principle of conservation of matter that made chemistry into a quantitative science, insofar as it did become quantitative. It is much more difficult to measure in chemistry than in physics or in astronomy. It is difficult to guess what to measure at all, since no such obviously and visibly measurable values as in the mentioned sciences exist. Classical analytical chemistry was capable of stating with more or less accuracy what and how much of a substance is contained in something, but this did not, in itself, disclose much on the internal order of substances. Chemistry became a quantitative science by the recognition of the weight proportions of the constituents in the compounds, by the development of stoichiometry. However, even after this all the mathematical apparatus needed in chemistry was the rule of three, whereas physicists of that period already operated with differential equations. Ever since, chemists have had an inferiority complex and have felt nostalgic towards higher mathematics. Nowadays this takes the form that chemists often force very impressive mathematical deductions into their papers, although these do not add anything essential to what the author wishes to communicate. In my own line (analytical chemistry) quite a lot of mathematical apparatus is being used that shows off very well at the blackboard or in print, but is eliminated in the actual determinations by using reference standards and operating with the good old rule of three. The chemists of the 18th century intuitively felt that there must exist some system expressible in numbers that defines the composition of compounds, i.e. that