RICHARDS. — ATOMIC WEIGHT OF STRONTIUM. 383 



free it as much as possible from clilorine (Stas). The mixture of pure 

 slightly moist hydrogen bromide, nitrogen, and hydrogen was now 

 dried by calcic bromide free from chlorine and iodine, and thus 

 became ready for use. 



The hard glass tube used for heating the platinum boat containing 

 the strontic bromide was ground very tightly into its socket of soft 

 glass, since it was not advisable to risk the presence of phosphoric 

 acid here. The powdered nearly anhydrous strontic bromide, haviug 

 been packed tightly into the boat and carefully pushed into position 

 in the fusion tube, was thoroughly dried at 200° in a stream of pure 

 air. The elaborate apparatus for preparing the mixture of gases was 

 now connected with the fusion tube, and when all the air had been ex- 

 pelled the boat was slowly heated to cherry-redness until the strontic 

 bromide was wholly fused. The temperature was then allowed to fall 

 a little below 600°, and the solidified bromide of strontium was freed 

 from any possible excess of hydrobromic acid by a current of dry hy- 

 drogen and nitrogen free from acid, delivered through a short-cut tube 

 (see page 382). 



The almost red-hot boat was now transferred as quickly as possible 

 to the light weighing bottle, within which it was allowed to cool. In 

 the preliminary work (and in Analyses 13 and 14) this bottle was 

 stoppered at once and cooled in an ordinary desiccator. Subsequently 

 an improved desiccator was devised for this purpose. A wide glass 

 tube capable of containing the weighing bottle was drawn out at one 

 end to a fine tube, which was fitted with a ground-glass stopper. The 

 other open end was made slightly conical and ground into a recepta- 

 cle which was in its turn attached to a drying tube containing fused 

 potash. The following sketch supplements this description. 



While the boat was still hot within the fusion tube, the stopper of 

 the weighing bottle was placed in the horizontal desiccator tube. The 

 moment after the transference of the boat into the bottle, both to- 

 gether were slid into the momentarily opened desiccator tube by 

 means of a glass rod which projected from the receptacle. The bot- 

 tle was held by means of a glass carriage during this manipul ition. 



The open weighing bottle, with its stopper and fused contents, could 

 now be heated indefinitely in a current of pure dry air at any tern- 



