M. Stas on the Determination of Atomic Weights. 199 



Another portion of iodate of silver was reduced by sulphurous 

 acid, and only the iodide of silver weighed. The iodate of silver, 

 after being dried at 180°, was weighed in exhausted flasks, then 

 heated to fusion, and freed from the last traces of water in a 

 current of air above 100°. It was then dissolved in dilute am- 

 monia and decomposed by sulphurous acid at 0°. From this 

 the composition of iodate of silver was calculated as follows:— 



Mean. 

 Agl . . 83-024 83-028 83-0239 83-0253 

 G . . . 16-976 16-972 16-9761 16-9747 



100-000 100-000 100-0000 1000000 



Hence the atomic weight of iodide of silver is in the mean 

 234-779, and the atomic weight of silver 107'928, and that 

 of iodine 126*857 (0=16), according to the synthesis of 

 iodide of silver. 



A complete synthesis of bromate of silver did not succeed ; for 

 on heating the salt there was finally and quite unexpectedly a 

 most violent explosion. Hence the salt, dried at 150°-160°, was 

 weighed in a glass bulb closed by a doubly perforated glass 

 stopper, in which delivery-tubes were ground. The salt was 

 fused in a current of dry air, which had been freed from organic 

 matter by being passed over heated oxide of copper ; it was then 

 fused, and after condensation of all aqueous vapour transferred 

 into weighed U-tubes containing pumice and sulphuric acid. 

 The salt was then reduced in the usual manner with sulphurous 

 acid. 100 parts of bromate of silver contain, 



Mean. 

 AgBr . 79-649 79*653 79-651 



The atomic weight of Ag Br is therefore = 187*87. Taking 

 into account the results of the synthesis of AgBr, the atomic 

 weight of silver is=107'921, and of bromine 79*91. 



Chlorate of silver was also reduced by sulphurous acid. This 

 salt is always rendered impure by traces of Ag CI, which arise 

 from the organic constituent's of the atmosphere. Like the iodate 

 and bromate, it persistently retains some water. It was there- 

 fore put into a large weighed glass flask, which was carefully 

 heated on the air-bath. At 243°-245° chlorate of silver fused, 

 and through it was passed a continuous current of pure dry air. 

 After cooling and weighing, the silver-salt was dissolved in water, 

 and the clear solution poured into another flask. In the first one 

 there remained only small traces of admixed chloride of silver, 

 which were weighed 'with the flask and allowed for. The solu- 

 tion of chlorate of silver was reduced by sulphurous acid. An 

 accurate investigation of the wash- waters showed that they con- 

 tained not a trace of silver dissolved. The chloride of silver 



