136 EUB1D1TJM AND CESIUM. PAET i. 



chloride of platinum free. Thus the precipitate of the 

 bichloride of rubidium and potassium is the least soluble 

 of the two. The yellow colour is evidently due to the 

 potassium. Caesium may be distinguished from potas- 

 sium by the same process. The carbonates, hydrates, 

 and other salts of the two metals were determined ; their 

 carbonates were shown to be readily separated, because 

 the carbonate of caesium is soluble in alcohol, which the 

 carbonate of rubidium, is not, and finally the metal 

 rubidium was separated. It has an extreme avidity for 

 oxygen, and burns in water like potassium, and possesses 

 many other analogous qualities. It melts at the tem- 

 perature of 38*5 Cent., and has a specific gravity of 

 1/-516. Bubidiuin is abundant in the mineral lepidolite 

 in many parts of Europe and North America, and M. 

 Grandeau has detected it in the ashes of beetroot, 

 tobacco, coffee, tea, and grapes by spectrum analysis. 

 It exists in various mineral waters, and in fact is very 

 general. Traces of various metals are met with in the 

 same vegetable ; thus the spectrum of tobacco gives lines 

 characteristic of lithium, potassium, rubidium, and lime. 

 Mr. W. Crookes discovered the new metal thallium by 

 means of its spectrum, which differs from every other in 

 having one bright green line upon a dark ground. He 

 obtained its various salts, and the metal itself, which he 

 describes as being heavy, dense, and very like lead, but 

 of greater specific gravity. Its fresh surface has a bright 

 metallic lustre, not so blue as that of lead, but it 

 tarnishes more easily. It is so soft that it can be 

 indented by the nail, yet it can be drawn into wire, and 

 in chemical properties it resembles mercury, lead, and 

 bismuth. Altogether it is more like a metal than a 

 metalloid, perhaps something between the two. Thal- 

 lium is completely volatilized at a temperature below 

 red heat, whether single or in composition. If the 

 quantity be small, the green line appears in a sudden 



