Analysis by Spectrum-observations. 341 



have employed this liquor as the source of the material which we 

 have used in the present investigation. 



The following observations served as the foundation for the 

 mode of separating the csesium-salts from the compounds of the 

 other alkalies. 



If the mother -liquors of the Diirkheim mineral water be freed 

 from alkaline earths by the ordinary methods, so that the mass 

 which remains after volatilization of the ammoniacal salts con- 

 sists solely of salts of the alkalies, and if the solution of these 

 salts be then treated with bichloride of platinum, a yellow cry- 

 stalline precipitate is obtained, which, when placed in the spec- 

 trum-apparatus, exhibits an intense potassium reaction, but 

 shows no trace of the blue lines of csesium. If the platinum 

 precipitate be boiled out twenty times with small quantities of 

 water, the successive solutions, as is the case with the rubidium 

 compounds, gradually become less and less yellow-coloured. 

 Examined from time to time in the spectrum-apparatus, the po- 

 tassium lines Ka, K/3 are seen to grow fainter and fainter, and 

 the blue caesium lines gradually become visible on the fading 

 background of the continuous potassium spectrum. The double 

 chloride of platinum and csesium is therefore, like the corre- 

 sponding rubidium-salt, more difficultly soluble than the chloride 

 of platinum and potassium. 



In our first experiment, conducted as above described, we 

 employed 50 grms. of the mother-liquor, and obtained only 1*2 

 milligramme of the impure double chloride of platinum and 

 cassium ; still, with this minute quantity, the spectrum reaction 

 was so well defined and characteristic that we did not hesitate at 

 once to commence the preparation of the salts of the new metal 

 on a large scale, in which 240 kilogrammes of mother-liquor, 

 obtained from 44,200 kilogrammes of water, was employed. 

 The difficulty of working up the immense mass of raw material 

 used in the preparation of the csesium-salts described in the pre- 

 sent memoir, was lessened by the kindness of Dr. Gundelach, 

 who arranged that the rougher portions of the operations should 

 be conducted in an alkali-works, in the following manner. 



The mother-liquors were treated with sulphuric acid in a salt- 

 cake furnace, and the sulphates thus obtained boiled for some 

 time with water containing caustic lime. The excess of lime 

 was separated from the aqueous solution by means of oxalic acid, 

 and then the greater part of the sulphuric acid precipitated with 

 nitrate of barium, whilst the last portions, together with the 

 soluble magnesian salts, w r ere removed by the addition of hydrate 

 of barium. The filtered liquid, neutralized by nitric acid, yielded 

 on evaporation a salt which was worked up in the Heidelberg 

 laboratory. 



