206 Mi Stas on the Determination of Atomic Weights. 



After solution in water the bromide of potassium from the pre- 

 vious experiment left traces of silica. Filtered through spongy 

 platinum, the filtrate decanted, after standing a day, was par- 

 tially evaporated and the residue fused in a current of nitrogen. 

 100 parts correspond to 110*360 parts K Br. The rest of the 

 solution of K Br was evaporated to crystallization, and the se- 

 parated salt divided into three portions. Each crystallization 

 obtained was fused in a platinum boat and in a current of ni- 

 trogen. Only in the presence of bromate of potassium does fusing 

 bromide of potassium attack platinum vessels. From bromide 

 of potassium once crystallized 110-312 parts were obtained for 

 100 parts silver; from twice crystallized, 110*346 j and from 

 the salt which had been three times crystallized, 1 10*338 parts 

 KBr. 



A fresh portion of bromate of potassium which had been five 

 times recrystallized was changed into K Br. 100 parts of 

 silver corresponded to 110*360 of this bromide of potassium. 

 The same salt, recrystallized in the manner just described, showed 

 the relation 100 Ag : 110-336 KBr. The mother-liquor and 

 wash-water from it evaporated, and a part of the residue ignited 

 in a current of bromine-vapour, gave a bromide of potassium 

 which exhibited the relation 100 Ag : 110*314 K Br. Another 

 part of the residue was changed into chloride by ignition in 

 chlorine gas, and this volatilized in a current of nitrogen. A 

 residue of 0*005 per cent, silica was left. 



Bromide of potassium from bromine and caustic potash. — In 

 order to prepare pure potash, pure cream of tartar was lixiviated, 

 heated almost to decomposition, then crystallized seven times, 

 and carbonized in a silver crucible. The carbonate of potassium 

 still contained silica, alumina, and traces of iron. It was de- 

 composed in a silver crucible by hydrate of lime prepared from 

 precipitated carbonate of lime. The lye was added to the bro- 

 mine, evaporated, and the residue exhausted with absolute alcohol. 

 The bromide of potassium was washed away by ice-cold water, 

 and the residue, bromate of potassium, repeatedly recrystallized 

 and at length ignited. After the separation of the bromate of 

 potassium, bromide of potassium was prepared from the mother- 

 liquor, which was heated to fusion. It was dissolved in bromine- 

 water, evaporated, and smartly dried. The salt then dissolved 

 completely in water. In the spectrum-apparatus this salt ex- 

 hibited no stronger reaction than other salts. 100 parts of 

 silver correspond to 110*332 and 110*343 parts of bromate of 

 potassium. 



Bromide of potassium from bromide of barium. — Bromate of 

 barium which had been four times recrystallized was precipi- 

 tated with carbonate of potassium. The filtrate evaporated, dis- 



