ME. W. CEOOIvES ON THE ATOMIC WEIGHT OF THALLIUM. 
325 
WEIGHT OF THALLIUM*. 
Weight of thallium taken ==183*783921 
Air displaced by thallium = (H)1S907 
183-802828 
Deduct air displaced by weights = 0-012596 
True weight of thallium in vacuo . . . 183-790232 
Collecting the data, we have 
f True weight of thallium in vacuo =183-790232 grs. 
,, „ nitrate of thallium in vacuo . . =239-646066 „ 
,, ,, glass in vacuo =766-133831 „ 
The reduction of the atomic weight from data obtained in the manner of the preceding- 
weighings becomes a case of simple proportion ; but the values found are absolute in 
so far only as the atomic weights of nitrogen and oxygen are correct. The atomic 
weights of nitrogen and oxygen have been usually represented by the numbers 14 and 16 ; 
but Professor Stas found these elements represented, according to observation, by 
14"009 and 15-960. Therefore, oxygen (0 3 ) = 47-880, and nitrogen =14*009, or N0 S 
= 61-889. According to the old equivalents, NO c =62. 
Taking as data the series of weighings in vacuo, the quantity of N0 3 required to 
convert the thallium into nitrate is 
(239*646066 — 183*790232=)55 *855834 grins. 
We have, then, with Professor Stas’s determination of the atomic weights of nitrogen 
and oxygen, the following proportion : — 
Weight of Weight of Atomic weight of Atomic weight 
N© 3 . thallium. NQ 3 . of thallium. 
55-855834 : 183-790232 :: 61-889 : a-; 
.*. #=203*642. 
This number, it will presently appear, represents the atomic weight of thallium as 
nearly as the possibility of error will allow. 
Let us see what would be the atomic weight of thallium if one or other of the correc- 
tions introduced into the above determination had been omitted. The use of the old 
equivalent ( = 62) for N0 6 , with the data derived from the weighings in vacuo, gives 
55-855834 : 183*790232 :: 62 : 204-007 
as the atomic weight; but I cannot admit this number to be so correct as 203-642. 
If we take the corrected weighings in air of ordinary density, we have with 
N9 3 = 61*889, 
55-827438 ; 183-783921 :: 61-889 : 203738. 
* To save needless repetition, I only give the results of these calculations. 
t In this determination the thallium and afterwards the nitrate of thallium were weighed in the same glass 
apparatus as described. 
MDCCCLXXIII. 2 X 
