212 M . Bunsen on the Preparation of Rubidium. 



The sulphuric acid from the combustion of pyrites contains 

 arsenic. To get rid of this, Kuhlmann placed a supplementary 

 chamber before the ordinary chambers in which the sulphurous 

 acid is converted into sulphuric acid, which was so large that 

 the gases becoming cooled deposited not only substances mecha- 

 nically carried away, but also volatile substances readily con- 

 densed, and especially arsenious acid. After some months of 

 a combustion of about 3000 kilogrammes of pyrites per diem, 

 considerable masses of arsenic and selenium are deposited, along 

 with mercury and thallium, amounting in some parts of the 

 deposit to ^ per cent. 



In works where this plan is not adopted, any thallium which 

 might be contained in pyrites would mix with the sulphate of 

 lead covering the floor of the first chamber, and would dissolve 

 in the sulphuric acid as fast as it was formed, so that the deposits 

 of sulphate of lead would contain traces of this substance so 

 small as to be inappreciable even to the spectroscope. 



The following observations on the preparation of rubidium 

 have been communicated by Prof. Bunsen in a letter to Prof. 

 Dumas*. 



The material for the purpose was extracted from the lepido- 

 lite residues left in the preparation of lithium. In separating 

 caesium from rubidium, use was made of the difference in solubility 

 of the neutral tartrate of csesium (which is deliquescent), and of 

 the bitartrate of rubidium, which is very little soluble t- 



The reduction of carbonate of rubidium by charcoal is more 

 difficult than that of sodium, and less so than that of potassium. 

 To effect it, the following mixture was heated in a potassium- 

 furnace : 89| parts of bitartrate of rubidium, 8 J parts of tartrate 

 of lime, and 2 parts of lampblack from turpentine. The metal 

 was received in a vessel containing naphtha ; 5 grammes of metal 

 w r ere obtained from 75 grammes of bitartrate. 



The metal melts at 38 0, 5, and its specific gravity is 1-516. 

 According to recent determinations at Heidelberg, sodium melts 

 at 95 0, 6, potassium at 62 0, 5, and lithium at 180°. 



Like potassium, rubidium burns on water with a rotatory 

 motion, and in its other properties has the greatest analogy with 

 that element. 



M. Dietzenbacher J has observed that the presence of a small 

 quantity of chlorine, bromine, or iodine modifies the properties 

 of sulphur to a remarkable extent. When a mixture of 400 

 parts of sulphur and 1 part of iodine is heated to about 180°, 



* Comptes Rmdus, January 26, 1863. 



t See also Mr. Allen's paper on the subject at p. 18.9 of the present 

 Number. J Ibid. January 5, 1863. 



