CHEMICAL SCIENCE. 175 



with a kind of lepidolite which contains three per cent, of rubidium ; 

 and that Mr. O. Struve, manufacturing chemist at Leipzig, is ready to 

 deliver a raw salt containing twenty per cent, of chloride of rubidium 

 at the comparatively moderate price of 23 francs the kilogramme. 



The Properties of Rubidium. Bunsen, who has succeeded in re- 

 ducing rubidium to a metallic state, thus enumerates its properties : As 

 a metal, it is very brilliant, like silver, white, with a scarcely perceptible 

 tinge of yellow. In the air it oxidizes instantly to bluish-gray suboxide, 

 and takes fire, after a few minutes, much more easily than potassium. 

 At -10 C. it is still as soft as iron : it melts at 58. 5 C., and below a 

 red heat is converted into a blue vapor with a shade of green. Ac- 

 cording to Bunsen, the true fusing point of sodium is 95.6 C., and that 

 of potassium G2.5 C. ; the latter does not pass through an intermediate 

 pasty condition in fusing. The density of rubidium is about 1.52. It 

 is considerably more electro-positive than potassium, takes fire upon 

 water, and burns with a flame which cannot be distinguished from that 

 of potassium by the eye. Rubidium burns with brilliancy in chlorine, 

 and in the vapor of bromine, iodine, sulphur, and arsenic. 



Additional Facts Respecting Thallium. This new metal, which was 

 first publicly shown at the London International Exhibition, 1863, has 

 since that time been produced in comparatively large quantities. At 

 the meeting of the British Association, 1863, Mr. Crookes, its discoverer, 

 exhibited a mass weighing upwards of a quarter of a hundred-weight, 

 and demonstrated its more obvious properties. It is the softest of the 

 new alkaline metals, being easily scratched by a point of lead. When 

 obtained, in larger quantity, thallium will doubtless be employed to 

 furnish a magnificent green flame. Eight parts of chlorite of thallium, 

 two of calomel, and one of resin, yields a splendid light on being ignited, 

 and a very little reduction in price would enable it to be used for 

 ship-signals ; its extraordinary intensity and monochromatic character 

 enabling it to penetrate through a hazy atmosphere, which alters alto- 



f ether the color of the ordinary green lights produced by the salts of 

 aryta. 



Mr. Crookes finds, in testing for thallium in the fine dust which 

 accumulates in the flues of furnaces burning iron pyrites, that the 

 spectrum analysis is comparatively useless from its extreme delicacy ; 

 ToVo P ar t f thallium in a mass being indicated as strongly and vividly 

 as the pure metal itself. Mr. Crookes has been experimenting upon 

 several tons of this dust. The most ready method of extraction he 

 finds to consist in washing it with pure water, acidulating the liquid 

 with hydrochloric acid, so as to convert the thallium into chloride. In 

 this manner, he has obtained from three tons of flue-dust sixty-eight 

 pounds of impure chloride, which was afterwards converted into 

 sulphate by heating with sulphuric acid ; this conversion into chloride 

 and reconversion into sulphate being repeated, in order to get rid of 

 impurities. Finally, the sulphate was reduced to the metallic state by 

 fusing with black flux or with cyanide of potassium. Thallium melts at 

 550 Fahr., and can consequently be easily fused over a gas jet, its 

 surface being protected from the air by a stream of coal-gas. Mr. 

 Crookes also detailed the following circumstances connected with the 

 discovery of this new metal : About three years ago he was engaged 

 in the examination of a residue from a sulphuric acid manufactory at 



