Cesium - Named From the Blue Sky

Once Bunsen and Kirchhoff had developed their spectroscope in the middle of the 19 century they were keen to use it to examine different natural products. Mineral waters were attracting great interest at this time. What did waters from different springs contain Why did they have effects on people s health In 1860 the two scientists wrote to the academy of sciences in Berlin  

We brought a droplet of mineral water from Durkheim into the flame in front of the spectroscope. Then we could recognize the characteristic lines of sodium, potassium, lithium, calcium, and strontium. From a larger water volume we precipitated calcium, magnesium and strontium with well-known chemical methods. The remaining solution was evaporated to dryness and the residues were moistened with nitric acid and dissolved in alcohol. From this solution lithium was precipitated with ammonium carbonate. 

The spectroscope revealed the presence of sodium, potassium and some lithium in the filtrate. In addition we observed two remarkable blue lines, very dose together. One of them was in the part of the spectrum where a well-known strontium line is situated. No element, earlier identified, has a pair of lines in this part of the spectrum. Our condusion is that we have discovered a new alkali metal and we propose the name cesium for this new element. 

The background of the name is the designation caesium, used by the ancients for the blue of the upper part of the firmament. 

In 1846, before the development of spectroscopy, C. F. Plattner, the metallurgy professor in Freiberg, had analyzed the mineral pollucite from Elba. He was recognized as a very clever mineral analyst but failed in this investigation. When he summed all the components he had determined, the total was 92.75%. After the discovery of cesium it was shown that pollucite has a considerable content of this element Plattner died in 1858 and never heard of the alkah metal that had created such great difficulties for him. 

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