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78.
How Germanium Was Discovered
In the beginning of March 1886 D. Mendeleyev received a letter which read: �Dear Sir, Allow me to present you with the reprint enclosed herein of a report from which it is evident that I have discovered a new element named �germanium�. At first I thought this element would fill the gap between antimony and bismuth in your remarkable and profoundly composed periodic system, and that the element would coincide with your eka-antimony, but the facts indicate that here we have to do with eka-silicon. �I soon hope to tender you more detailed information on this interesting substance; today I content myself with informing you of a very probable new triumph of your ingenious investigation and take the opportunity to express my deep respect for you. Faithfully yours, Freiberg, Saxony, Not in vain, it appeals, did Henry Cavendish almost a hundred years before the discovery of germanium, repeat time and time again that �everything is determined by measure, number, and weight.� In analysing argyrodite, a rather rare mineral discovered not long before in Saxony, Clemens Winkler found it to contain mainly silver and sulphur with small quantities of iron, zinc and mercury. But what surprised him was that the percentages of all the elements found in argyrodite added up to only 93 and stubbornly refused to make 100. What could the elusive 7 per cent be? The methods of analysis of most of the elements known by that time were well worked out and not one of them should have escaped the chemist�s eye. Then Winkler made the daring assumption that since these 7 per cent had escaped him with the existing analysis procedures, they must belong to an unknown element. His assumption was fully confirmed By slightly changing the procedure of the analysis Winkler isolated the elusive 7 per cent and proved them to belong to a new element, unknown at that time, which he named germanium in honour of his native land. Gravimetric analysis played an important part in the discovery of one more element, namely, argon, a representative of the zero group of Mendeleyev�s Periodic System. In the early nineties of last century the English physicist Rayleigh undertook a determination of the density of gases, and hence of their atomic weights. All was well until the investigator came to nitrogen. Here strange things began to happen. A litre of nitrogen separated from air weighed 0.0016 gram more than the same amount of nitrogen produced from chemical compounds, the kind of compounds having no effect on the final result. The ill-starred litre of nitrogen obtained from ammonium nitrite, nitrous or nitric oxides, urea, ammonia, or other compounds, invariably proved to be lighter by the same amount than atmospheric nitrogen. Not having found the reason for this strange difference, Rayleigh published an article in the London journal �Nature,� describing his results. Soon the chemist Ramsay responded and the investigators combined their efforts in an attempt to solve the riddle. In August 1894 they reported the discovery of a new element, the cause of Rayleigh�s first failures. Its content in the air was found to be about one per cent. Thus ordinary gravimetric analysis helped scientists to discover new elements. Not a single chemical laboratory can get along without it even today. In the long run ordinary weighing helps to determine the percentages of elements in complicated compounds and minerals. Of course, it must be preceded by painstaking chemical operations of separation of the elements from one another. |
