62 Mr. W. Crookes on the Discovery of the Metal Thallium. 



In addition to this positive evidence, I will also refer to the pro- 

 babilities of the case. Though M. Lamy's results were said to be 

 obtained within the short space of one month, both he and his 

 friends assume that, during the whole year that elapsed between 

 my first publications on thallium and the exhibition of the spe- 

 cimens in 1862, I had either ceased to work on the subject, or 

 that my knowledge of the element had not advanced one step 

 between May 1861 and May 1862; that the black powder I 

 exhibited as thallium was obtained by precipitating with hydro- 

 sulphuric acid, not the black powder described as precipitated 

 by zinc*. They assume that because at the former date I was, 

 though doubtful as to the point, inclined to class thallium with 

 the semimetals, therefore at the latter date I was ignorant that 

 it possessed true metallic properties. 



I trust the improbability, nay, the impossibility of this being 

 the case, will be recognized by every chemist who has examined 

 thallium. It is an element as easily reduced to and preserved 

 in a metallic state as lead : can it, then, be imagined that I, 

 who was so much interested in determining its characters — who 

 had been for twelve months leaving no means untried to obtain 

 a more copious source of thallium — who during that time had 

 scarcely for a day relaxed working on this subject exclusively — 

 is it likely, I say, that I should have been such an egregious 

 blunderer as not to find out that it was a metal? Why, as 

 soon as I had obtained a dozen grains of one of its com- 

 pounds fairly pure, I could scarcely try the simplest experiment 

 without having the fact of its metallic character forced upon 

 me in too positive a manner to admit of doubt. Consistent 

 with this probability that I considered thallium to be a metal, 

 is the fact that it was exhibited as being a metal. 



Having thus stated the grounds on which I claim the dis- 



where it presented a coherent metallic appearance, of dark colour, but 

 which, when freshly scraped with a knife, gave a coloured metal similar to 

 lead. You also had a larger quantity precipitating on platinum in the 

 spongy form, which, compressed, gave metallic lustre, and when tried in 

 the spectroscope, gave the green line magnificently. 



* * % * * jj< 



" I remain yours very truly, 

 " W. Crookes, Esq., F.C.S." " John Williams." 



" having ourselves been shown by Mr. Crookes the wonderful 



green line in the spectrum in 1861, and a small disc of the metal itself in 

 January 1862, — dates earlier than any referred to by Lamy in the late con- 

 troversy." — The London Review, April 4, 1863. 



* In my first paper in this Journal for April 1861, I wrote, "From its 

 hydrochloric acid solution it is readily precipitated by metallic zinc in the 

 form of a heavy black powder, insoluble in the acid liquid." 



