Scientific Intelligence. 



' the precipitant. 



Chromate of Thallium is a pale-yellow precipitate soluble in acids and re- 

 precipitated upon neutralization with ammonia. 



protochlorid of tin, oxalic add, carbazotic add, sulphurous add, or protosulfhaU 

 ofiron. 



The reactions are sufficient to prove chemically that the body tinder 

 examination is a new element. Its behavior in the spectrum apparatus is 

 perhaps the most conclusive test upon this point. When a minute per- 

 tion of the metal (the sulphid, chlorid, or in fact, any compound of thal- 

 lium) is introduced into the flame of the spectroscope, it immediately 

 produces a single green line, perfectly sharp and well defined upon a 

 black ground, and of extraordinary purity and intensity, almost equal to 

 the sodium-line in brilliancy. It' is not,' however, very lasting. Owing 

 to its great volatility, a portion introduced at once into the flame merely 

 shows the line as a brilliant flash, remaining only a fraction of a second; 

 but if it be introduced into the flame gradually, the line continues pres- 

 ent for a much longer time. If, also, a piece of metallic thallium be in- 

 troduced into the flame on a platinum wire loop, they fuse together, and 

 the alloy gives the green line rather more permanently, although of course 



Working c 

 free from sod 



substance is held on a loop of platinu 

 is most brillia^^ -^ i i 



this ready means of produ( 



could not fail to be applicable" to some useful purpose! 



The green line of the thallium spectrum appears to be unaccompanied 

 by any line or band in other parts of the spectrum. A flame of suft- 

 cient temperature to bring the orange line of lithium into view produces 

 no addition to the one Lhallium-line ; and an application of telescopic 

 power strong enough to separate the two sodium-lines a considerable dis- 

 tance apart still shows the thallium-line single. I consider therefore that 

 I am justified in stating that thallium produces the simplest spectrum of 

 any known element. Theoretical inquiries into the cause of the spectrum 

 lines, and their relation to other constants of an element, may be facihta- 

 ted now we know a metal which gives rise to luminous vibrations of only 

 one degree of refrangibility. The remarkable simplicity of the thallium 

 spectrum offers a strong' contrast to the complicated spectra given Dy 

 mercury, bismuth, and lead—the metals to which it has the most chem- 

 ical resemblance. 



The position of the green line does not coincide with any definite Ime 

 in the solar spectrum. According to Kirchhoff's theory, we "?"^^ ^^^^^^ 

 fore assume that thallium is not present to any great extent in the s • 

 Under the highest telescopic power of my apparatus, the line appears 

 be absolutelv irlftntioal in rAfrano.;Kn;t«^ rcUV, -. c>,orn well-defined line m 

 nd Kirchhoff bav^ 



