THALLIUM. CROOKES. 121 



laboratory record only after freeing the same from the 

 blunders, fraud and folly which seem inseparable from the 

 personality known as William Crookes. 



The Atomic Weight of Thallium. 



Ad rent : Under these conditions it will be advisable to 

 determine the atomic weight of thallium, independently of 

 the earlier work of Crookes. 



There is the electrolysis of thallium sulphate effected by 

 Lepierre in 1893. He made 3 determinations on between 

 i and 3 grammes of the sulphate. The extreme ratios 

 run from 954 to 945, exhibiting a range of only 9. The mean 

 analytical ratio is 0.80 953, which is only i high, for the 

 atomic ratio is 



Th : Th O4 8 = 408 1504 = 0.80 952. 



The same chemist made 2 determinations on between 2 

 and 4 grammes of thallous oxide, which he dissolved and 

 submitted to electrolysis. 



The atomic ratio for this process is 



Th : Th Oa = 408 : 456 : 0.89 474, 



while Lepierre obtained in the first determination 13 more, 

 and in the second, i more ; his mean thus is only 7 high. 



Accordingly, there can be no doubt about the atomic 

 weight of thallium. It is 204, exactly. 



We have a number of other determinations, but they are 

 mostly made according to faulty methods and therefore do 

 not count here. 



Thus, the inferior silver chloride process, according to 



Tl Cl : Ag Cl = 239.5 : H3-5 = i-6 937, 

 gave Lamy, 1863, values differing in range by 938 ; the mean 

 was 23 low. Such determinations are worthless, of course. 



Hebberling, in 1865, obtained a mean 472 low, and Wells 

 and Penfield, 1894, obtained as mean 405 high. This shows 

 again simply that the method is bad, and that these chemists 

 did not know it. 



The reaction 



Tlz O4 S : BaO* 8 = 504 : 233 = 2.16 309, 

 has also been used, but is notoriously far from reliable. 



