MR. W. CROOKES OK THE ATOMIC WEIGHT OF THALLIUM. 
311 
of thallium are then quickly removed from the warm water of the carbonic-acid bath, 
rapidly wiped dry with warm cambric while in the carbonic acid, and put into the 
weighed tube of water. It is found that no appreciable oxidation takes place during 
this transference, and that the whole of the moisture can be removed. The tube and 
its contents are then weighed again. 
Fig. 8 represents a vessel for the conversion of thallium into its nitrate, the pure 
metal as weighed in the manner described above in a tube of water being placed in the 
bulb a, and the pure nitric acid in b. The tubes are accurately ground and fitted to 
each other at c. d is a permanent stopper to the upper bulb, well ground, e and f are 
platinum wires for the support of the flask in the balance. The process of converting 
the thallium into its nitrate coincides in detail with this apparatus with the process 
ultimately adopted, and particularly described in the succeeding pages. With an appa- 
ratus of this kind the determination A was performed, the metal being purified by the 
process already described under a (p. 308). 
Fig. 9 is a further improvement. The nitric acid in acting upon the metal in a 
evolves fumes, which mechanically carry off traces of nitrate of thallium. In the vessel 
shown in fig. 8 these fumes are washed in the nitric acid, offering, however, no great 
advantage ; but in the series of bulbs shown in fig. 9, b contains the nitric acid, which 
can, by means of the tap c, be admitted in the required quantity to the metal. The 
fumes are washed in the water contained in c/, the water being evaporated to obtain the 
nitrate of thallium held in solution. In this apparatus, and with metal purified by the 
process described under the letter the determination B was effected. The metallic 
thallium is weighed sealed up in hydrogen in the following manner : — 
The lump or ingot of pure metallic thallium prepared by the process a, already 
described, is cut up into parallelograms, all the original surface being removed with a 
very sharp steel knife. The parallelograms, immersed and boiled in very dilute sul- 
phuric and hydrochloric acids, are subsequently washed, boiled repeatedly in water, and 
then transferred to the glass tube a, fig. 10. Into this tube pass and are fused the 
platinum wires b , c, these wires being the reducing and oxidizing electrodes respec- 
tively in connexion with two Grove’s elements. At d the tube is drawn out to a fine 
orifice, and at e is passed in a current of pure hydrogen prepared as before described, as 
shown in fig. 10 a. The electric current being passed through the water, to preserve the 
j pure metallic surface of the thallium, heat is applied until the water is entirely volatilized. 
At this point, and while the tube is very hot, the dry hydrogen still passing, the end of 
the tube at d is sealed up, and then the tube at h, previously much contracted, is closed 
before the blowpipe. The metal is thus enclosed hermetically in an atmosphere of pure 
hydrogen. The tube and its contents are then cooled for six hours, and when cooled, 
weighed first in air and then in the vacuum-balance. The tube is now cut across the 
middle with a cutting diamond, wrapped up in smooth platinum-foil to secure any 
splinters of glass which might be thrown off, and then broken with a sharp blow oppo- 
site the cut. The thallium is carefully removed from the pieces of tube, and introduced 
2 t 2 
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