192 ANNUAL OF SCIENTIFIC DISCOVERY. 



discover ^oW * TpW P ar ^ ^ a milligramme of quinine. This ex- 

 traordinary sensibmty exceeds anything that the analysis of the alka- 

 loids has furnished to this time, the reactions of strychnia only show- 

 ing a close approach to such great acuteness. 



THE NEW METAL THALLIUM. 



This new metal, it will be remembered (see Annual of Scientific 

 Discovery, 1862), was discovered last year by Mr. Crookes, of England, 

 by means of the new process of spectrum analysis, in the residuum left 

 after the combustion of sulphur for the manufacture of sulphuric acid. 

 The name thallium is derived from the Greek dahhog or Latin thal- 

 lus, a budding twig, a word which is frequently employed to ex- 

 press the beautiful green tint of young vegetation, chosen on account 

 of the green line which it communicates to the spectrum, recalling 

 with peculiar vividness the fresh color of early spring. 



From researches undertaken by Mr. Crookes, since the first discov- 

 ery of this new body, it would appear to be by no means a very rare 

 substance, as he states that he has found it in many mineral ores 

 from various localities. It was present in more than one-eighth of the 

 specimens in a large collection of cupriferous pyrites from different 

 parts of the world ; he has rarely found it, however, in pyrites in 

 which copper was absent. In most cases it s is only necessary to 

 powder a small fragment of the mineral and ignite a little of it in the 

 flame on a moistened platinum wire, when the green line is distinctly 

 seen in the spectroscope. Mr. Crookes thinks that in some of the 

 large English copper, sulphur, and sulphuric-acid works, thallium is 

 now thrown away by the hundred-weight. A slight modification of 

 the present arrangements of the furnaces and condensing flues, or 

 even an examination of some of the residues, would enable nearly the 

 whole of this to be saved. Owing to the frequent occurrence of thal- 

 lium in copper ores, it is very probable that this element may some- 

 times be present in commercial copper, and may give rise to some of 

 the well known but unexplained differences of quality. 



The following, according to Mr. Crookes, are the properties of the 

 new metal : " In the pure state it is a heavy metal, bearing a remark- 

 able resemblance to lead in its physical properties. Its specific grav- 

 ity is, however, higher about twelve. The freshly-scraped surface 

 has a brilliant metallic lustre, not quite so blue in color as lead, and it 

 tarnishes more rapidly than this latter metal. It is very soft, being 

 readily cut with a knife and indented with the nail ; it may also be 

 hammered out and drawn into wire, but has not much tenacity in this 

 form. It easily marks paper. The fusing point is below redness, and 

 with care several pieces may be melted together and cast into one 

 lump. There is, however, generally a loss in this operation, owing to 

 its rapid oxidation. The metal itself does not appear to be sensibly 

 volatile- below a red heat. I have made 110 special attempts at present 

 to determine the atomic weight, although, from two estimations of the 

 amount of sulphur in the sulphide, it appears to be very heavy. The 

 figures obtained did not, however, agree well enough to enable me to 

 speak more definitely on this point than that I believe it to be above 

 one hundred. Thallium is soluble in nitric, hydrochloric, and sulphu- 





