840 Professors Kirchhoff and Bunsen on Chemical 



siting on boiling as a fine heavy powder, which, examined under 

 the microscope, is seen to consist of small shining regular 

 octahedrons, transparent, and of a honey-yellow colour. The 

 compound is quite insoluble in alcohol, and much more difficultly 

 soluble in water than the corresponding potassium salt. 100 

 parts of water dissolve of this salt — 



at 6-0C 0-193 part 



at 13-5C 0135 „ 



at 48-OC 0-195 „ 



at 60-OC 0-263 „ 



at 100-OC 0-641 „ 



The above numbers are the mean of a number of experiments 

 which agree so well amongst themselves, that the result given 

 at 13°"5 C. as the minimum of solubility may be regarded as 

 certain. This seems to show that at a lower temperature the 

 salt contains water of crystallization. 



The bichloride of platinum in the salt loses some of its chlorine 

 when a current of hydrogen is passed over it in the cold • and the 

 whole of this chlorine completely disappears when the salt is 

 heated, leaving a residue of chloride of rubidium and metallic 

 platinum. For the purpose of analysing the salt, 1*9398 grm. 

 of the double salt prepared from pure bichloride of platinum, 

 and completely dried at 150° C, was reduced in a current of 

 hydrogen, and thus lost 0'4850 grm. The chloride of rubi- 

 dium, obtained by extracting the residue with water, weighed 

 0-7891 grm., and yielded 0-9252 grm. chloride of silver. The 

 reduced platinum weighed 0*6620 grm. Hence the composition 

 of the salt is found to be — 



Calculated. Found. 



t,. , , ., , , ,- fPt. . 91-10 3408 34-13 



Bichloride of platmum| cl2 _ ^.^ ^^ ^ m 



ril ., , ,- r jfRb . 85-36 29-35 28-88 



Chloride of rubidium .^ C1> 35 . 46 12 - 19 n . 79 



282-84 100-01 99-80 



The somewhat considerable deviation of the found from the 

 calculated numbers is to be accounted for by the fact that the 

 reduction of the salt was made in a crucible with a perforated 

 lid, and that a small quantity of the chloride of rubidium was 

 thus volatilized. 



III. Of the Occurrence, Preparation, and Atomic Weight of the 

 Ccesium Compounds. 



We have always found this metal associated with sodium, 

 potassium, and rubidium. It occurs in the largest quantity in 

 the mother-liquor from the mineral water of Durkheim • and we 



