BUNSEN MEMORIAL LECTURE. 6ii8 



have been prepared by a .simple process as a bye-product. I uni .•alii,,- 

 the new metal N;a^sium; from 'aesius' blue, on account of th7. 

 splendid blue line in its spectrum. Next Sunday J hope to find time 

 to make the lirst determination of the atomic weight." 



The rare combination of mental and manual dextei-ity cliaractei-istic 

 of Bunsen is nowhere more strikingly shown than in the investigation 

 of the cesium compounds. From these 17 grams of ca^sium chloride, 

 obtained as above described, he not only succeeded in preparing and 

 analyzing all the more important compounds, but in crystallizing the 

 salts in such a form that he was able to determine their crystallo- 

 graphic constants and then to supply all the necessary data for tixiiig 

 the position of this new element and its compounds in relation to its 

 well-known relatives, potassium and sodium. 



All the w^orld knows that shortly after his discovery of ceesimn the 

 birth of another new alkali metal, rubidium' (Berlin Monatsh., IhtJl, 

 (6), 273), was announced by Bunsen, and the application of spectrum 

 analysis led, in other hands, to the isolation of thallium in 1861, indium 

 in 1863, germanium in 1886, gallium in 1875, and scandium in ls7i», 

 but alongside of these came announcements of the discovery of other 

 new metals whose existence was more than doubtful. Concerning 

 these he writes to m3''self : 



"The frivolous wa}^ in which new metals are now discovered by 

 dozens and sent forth into the world duly christened is certainly no 

 gain to science; onl}^ later inquirers will be able to decide what 

 remains new and serviceable out of this chaos of material." 



I may here remind you that cjesium is not only interesting as being 

 the first metal to have been discovered ])y spectrum analysis, but 

 because, even before 15unsen\s discovery, chemists had worked with 

 csesium salts which they had mistaken for potassium compounds, so 

 closely do the properties of the two metals coi-res])on(l. IMattner, in 

 1846, analyzing a mineral from Elba termed "pollux," could not bring 

 his anah^sis to add up to 100 parts and was unable to explain the 

 anomaly. After Bunsen had established the existence of ca'sium. 

 Pisani, in 1864, took up the reexamination of the mineral and showed 

 that the alkali metal was cajsium, with an atomic weight of i:il.".>, and 

 not potassium, with one of 38.85. thus accoiinfing for the mi.ssiiig 

 percentage. 



In the Christmas vacation of 1863 an extraordinary accident, illus- 

 trating in a painful manner the close analogy which exists between 

 the properties of the potassium compounds and those of rubidium, 

 occurred in Bunsen's laboratory. It is thus desciil»e(l in a Ictt.T fn.ui 

 Bunsen to myself: 



"For a week I have been in a very depressed and sad state of mind 

 owing to a fearful misfortune which has taken i)l:icc m the l:il.o.;.tory. 



~ 1 Aulus gellk^cte^Attka. II, 26. - Kubidiii. autc-.n e-.t vuiu. atriur ot uigro.v 

 multo inustus." 



