THE FUSION OF ARGENTIC SULPHATE. 77 



rent of air could then be either used in a pure dry state by passing through 

 L or F, or else charged with sulphur trioxide by bubbling twice through 

 fuming sulphuric acid in the bottle E. This acid was kept saturated by 

 an excess of solid sulphur trioxide. A current of air mixed with any 

 desired proportion of sulphur trioxide was thus delivered through G into 

 the quartz tube H. The delivery tube (G) and the quartz tube (H) 

 touched each other, but no attempt was made to secure a tight joint. 



Fig. 4. Apparatus for delivering appropriate gases into the quartz tubes. 



The argentic sulphate contained in the quartz tube was then fused with 

 a fish-tail Bunsen burner held in the hand. A red heat is required. When 

 all of the sulphate was fused, the stopcock (P) delivering sulphur trioxide 

 was closed and a rapid current of air was admitted through F. As soon as 

 the fumes of sulphuric acid could no longer be seen escaping from the end 

 of the quartz tube, the flame was removed and the tube was slowly rotated 

 by drawing out the platinum wire wrapped around one end. This causes 

 the argentic sulphate to solidify in a thin sheet around the tube. Unless 

 care is taken to keep the salt at least 1 cm. distant from either of the end 

 tubes, difficulty is experienced during the conversion into chloride. 



The final solidification in the current of pure dry air was carried out 

 very rapidly, in order to avoid decomposition and obtain a perfectly white 



