CAPACITY FOi; Hi AT OF METALS AT DIFFERENT TEMPERATURES. 185 



allowed to cool. If a thick film is desired, additional coatings can be given. Care 

 should be taken to prevent contamination by flame-gases ; if this occurs the surface 

 should be brightened by means of ordinary metal polish. 



The next step is to " tin " the surface, and this requires care. The tube is gently 

 heated and rubbed with a lump of resin ; the solder melted on with a clean soldering 

 iron which should be only sufficiently hot to just melt the solder. With care the 

 entire platinised surface may be coated with an irregular coating of solder. Vigorous 

 rubbing of the surface with the soldering iron should be avoided, as it would probably 

 tear the film away from the glass. 



The tube is then ready to be soldered into the metal ferrule which should be 

 " tinned " on the inside. 



VOL. CCXIII. A. 2 B 



