ALUMINUM. 1 J: 



Series B. 



12.1023 grm. of the alum gave 1. 3660 grm. AljOg. 11.2S7 per cent. 



10.4544 " 1. 1796 " 11.283 " 



6.7962 " .7670 " 11.286 " 



8.5601 " , -9654 " 11.278 " 



4.8992 " .5528 " 11.283 " 



Mean, 11.2834, ±: .0011 



Combined, these series give a general mean of 11.2793, ih 

 .0008. Hence Al = 27.075, =i= .011. 



The aluminum bromide used in the second series of ex- 

 periments was prepared by the direct action of bromine 

 upon the metal. The product was repeatedly distilled, the 

 earlier portions of each distillate being rejected, until a con- 

 stant boiling point of 263.°3 at 747 mm. pressure was noted. 

 The last distillation was effected in an atmosphere of pure 

 nitrogen, in order to avoid the possible formation of oxide 

 or oxy-bromide of aluminum ; and the distillate was col- 

 lected in three portions, which proved to be sensibly identi- 

 cal. The individual samples of bromide were collected in 

 thin glass tubes, which were hermetically sealed after nearly 

 filling. For the titration pure silver was prepared, and 

 after fusion upon charcoal it was heated in a Sprengel vac- 

 uum in order to eliminate occluded gases. This silver was 

 dissolved in specially purified nitric acid, the latter but very 

 slightly in excess. The aluminum bromide, weighed in the 

 sealed tube, was dissolved in water, precautions being taken 

 to avoid any loss by splashing or fuming which might re- 

 sult from the violence of the action. To the solution thus 

 obtained the silver solution was added, the silver being 

 something less than a decigramme in deficiency. The re- 

 maining amount of silver needed to complete the precipita- 

 tion of the bromine was added from a burette, in the form 

 of a standard solution containing one milligramme of metal 

 to each cubic centimetre. The final results were as follows, 

 the figures in the third column representing the quantities 

 of bromide proportional to 100 parts of silver. Series A is 

 from the first portion of the last distillate of AUBrg; .series 



