406 THALLIUM. 



metals or any of their salts. Thallium on the other hand, which was^ 

 discovered much later than the two last mentioned, is now manufac- 

 tured in large quantities, has been tolerably well investigated and 

 promises to be of considerable n&e in some of the industrial arts. 



It is curious to remark that two if not three of these metals for the 

 discovery of which we are indebted to spectrum analysis, should be 

 found to belong to the class of the alkalic metals, for ceesium and 

 rubidium are so similar as to be with difficulty distinguished from 

 potassium, and thalliiim which was at first ranked with lead, is now 

 by many associated with the alkalies or rather forms a connecting 

 link between two groups, exhibiting some of the characteristic proper- 

 ties of feoth. 



On this account thaHium is one of the most isteresting metals, and 

 as the different papers describing its combinations are scattered through 

 Tarious journals, the following resume may not be without interest 

 to our chemical readers. 



The new metal seems to have been discovered independently both 

 by Mr. Crookes and M. Lamy, but the priority is due to the former, 

 who discovered the element in March 1861, and had prepared several 

 of its compounds as early as January 1862, and at the time of the 

 exhibition in 1862 was quite aware of its metallic character, although 

 M. Lamy had succeeded in obtaining: it in a denser form exhibiting 

 completely its claim to the character of a metal. 



Both chemists obtained it originally from some seleniferous deposits 

 from the chambers of a sulphuric acid factory, and as it will be- 

 lecoUected that Berzelius discovered selenium in his examination of 

 such a deposit from Gypsholm it feecame interesting to ascertain 

 whether that substance had contained thallium as it would not in all 

 probability have escaped detection under the hands of so acute a 

 chemist as the Swedish philosopher. Fortunately, Mr. Crookes was. 

 enabled to examine some of the original Gypsholm deposit, and found 

 it to contain no trace of thallium. 



The new metal seems to be very widely distributed, existing im 

 native sulphur and in most pyrites, and in many other ores and com- 

 mercial products.^ It has also been detected in the mineral water of 

 Nauheim and in lepidolite and mica, although it has been objected 

 that possibly the thallium may have been contained in the reagents 

 employed, as was proved to be the case with arsenic some years since. 



The principal source of thallium appears to be the different kinds 



