Scientific Intelligence. 



cut. It appears yellowish when rubbed against a hard body ; but this lint 

 is doubtless due to oxydation, for the metal precipitated by a battery from 



bluish grey tinge, which resembles aluminium. 



Thallium is very soft, and very malleable; it can be easily scratched 

 by the nail, and cut with a knife. It marks paper, leaving a yellowish 

 streak. Its density (11-9) is a little higher than that of lead. It fuses 

 at 290° C, and volatilizes at a red heat. Lastly, thallium has a great 

 tendency to crystallize, for the ingots obtained by fusion crackle like tm 

 when they are bent. But the physical property, par excellence, of thal- 

 lium,— that which, according to the beautiful researches of MM. Kirch- 

 hoflF and Bunsen, characterizes the metallic element,— that which led to 

 its discovery,— is the property which it possesses of communicating to 

 the pale gas-flame a green color of great richness, and to the spectrum ot 



yellow ray of sodium, or the red ray of lithium. On the raicrornetric 

 scale of my spectroscope this ray occupies the division 120-5, that of so- 

 dium being at 100^. The slightest portion of thallium, or of one of its 

 salts, gives the green line with such brilliancy that it seems white. The 

 fifty-millionth part of a gramme can, according to my calculations, be re- 

 cognized in a compound. 



Thallium tarnishes rapidly in the air, becoming covered with a thin 

 pellicle of oxyd, which preserves the rest of the metal from alteration. 

 This oxyd is soluble, is decidedly alkaline, and has a taste and smell sira- 

 liar to potash. By this characteristic, as well as by its optical properties, 

 thallium approaches the alkaline metals. 



Thallium is attacked by chlorine, slowly at the ordinary temperature, 

 rapidly at a temperature above 20a' C. The metal then melts, become 

 mcandescent under the action of the gas, and gives rise to a yellowisn 

 lifies on cooling to a mass of a little paler color. 



bromine, sulphur, and'phosphorus can also combine with thal- 

 , sulphids, ai 



this liquid at the temperature 



L'Mjjmg loaias, Dromids, sulphids, and phosphids. 

 ntly-prepared thallium preserves its metallic lustre ii 



but, by the aid of an acid, it separates its elements, disengaging hydrogen. 

 Sulphuric and nitric acids are those which attack thallium easiest, es- 

 pecially by the aid of heat. Hydrochloric acid even boiling dissolves" 

 with difficulty. Under these circumstances, there form white so ube 



salts, sulphate, and nitrate, crystallizing readily, and a slightly i 

 chlond, but capable also of crystallizing. , „, 



Natural State and Extraction.— IhsWrnxn cannot be considered.^ 

 ^ery rare in nature. It exists, indeed, in many kinds of pyrites, whica 

 are used at the present time in farge quantities, principally for the manu- 

 facture of sulphuric acid. I may especially mention Belgian pyrit^ f^ 

 Theux, Namur, and Philippeville. I have also found it in mioeralogica' 

 specimens from Nantes and Bolivia, in S. America. * * * * . 



As to the metal itself, it may be reduced from one of its saline combi- 

 nations either by the decomposing action of an electric current, or bj 

 precipitation with zinc, or by reduction with charcoal at a high temF*' 



