44 



The New Metal Thallium. 



specific gravity is about 12, that of lead being 11*36. Mr. 

 Crookes says it is not so blue as lead, and M. Lamy describes 

 it as less white than silver, and resembling aluminium in hue. 

 A fresh cut surface has a brilliant lustre, which tarnishes quicker 

 than lead. It is soft enough to be scratched with the nail, and 

 very malleable, but possessed of little tenacity. It readily marks 

 paper, leaving a trace " with yellow reflexions." M. Lamy 

 also states that it becomes yellowish if rubbed with a hard 

 substance, a change which he attributes to oxydation. It is 

 so sensitive in the spectroscope that the last named authority 

 affirms that it may be discovered in one fifty millionth of a 

 gramme of one of its compounds. Mr. Crookes describes two 

 oxides of thallium, and thinks that a third is probably formed. 

 To one he ascribes basic properties, and we presume it is that 

 which is formed when the metal tarnishes, and which M. Lamy 

 states to be alkaline, with an odour like that of potash. The 

 next oxide, containing more oxygen, Mr. Crookes names thallic 

 acid, which may be obtained in a crystalline form. 



Iodine, bromine, sulphur, and phosphorus can unite with 

 the new metal, and it combines with sulphuric, carbonic, chro- 

 mic, phosphoric, and other acids. 



.M. Lamy exhibited to the French Academy an ingot of thal- 

 lium weighing fourteen grammes, obtained by a Bunsen battery 

 from chlorides which he formed by chemical means. The new 

 metal is far from rare, and is very likely to be extracted in 

 sufficient quantities to serve some economic use. Its spectro- 

 scope properties are highly important. In the words of Mr. 

 Crookes, " 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 sufficient temperature to bring the 

 orange line of lithium into view produces no addition to the 

 one thallium line ; and an application of telescopic power strong 

 enough to separate the two sodium lines a considerable distance 

 apart, still shows the thallium line single. I consider, there- 

 fore, 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 facilitated when 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 by mercury, bismuth, and lead, the metals to 

 which it has most chemical resemblance." 



