462 Prof. E. J. Chapman on some Blowpipe Reactions. 



in carbonate of soda, metallic oxides fall into three groups : — 

 (1) Easily soluble, e.g. PbO, Bi 2 3 , BaO, &c; (2) Slightly 

 or partially soluble, e.g. Mno0 3 CoO, &c; and (3) Insoluble, 

 e. g. Fe 2 3 , Ce 2 3 , NiO, OaO, MgO, &c. 



On the Detection of Bromine in Blowpipe Experiments. — 

 "When fused with phosphor-salt and copper oxide, the bromides, 

 it is well known, impart an azure-blue coloration to the flame, 

 much like that produced by chlorides under similar treatment, 

 although streaked more or less with green, especially at the 

 commencement of the operation. To distinguish these bodies 

 more closely, Berzelius recommended the fusion of the test 

 substance with 6 or 7 volumes of bisulphate of potash in a 

 closed tube. Bromides by this treatment become decom- 

 posed, as a rule, and give off strongly smelling brownish 

 or yellowish-red vapours of bromine. But this process does 

 not always give satisfactory results, as in some instances the 

 bromide is very slightly attacked. In this case, the following- 

 method, based on a peculiar reaction of bromide of silver, first 

 pointed out by Plattner, may be resorted to. If insoluble, 

 the bromide is fused with 2 or 3 volumes of carbonate of soda. 

 A soluble bromide of sodium is thus formed, with separation of 

 the base. To the filtered or decanted solution of the fused 

 mass a small fragment of nitrate of silver is added, in order 

 to precipitate bromide of silver. This, collected by decanta- 

 tion, is fused with a small quantity of bisulphate of potash in 

 a little flask or test-tube. The bromide of silver will quickly 

 separate from the flux in the form of a blood-red globule, 

 which becomes pale-yellow when cold. The little globule, 

 washed out of the tube by dissolving the fused bisulphate in 

 some warm water, is carefully dried by being rubbed in a 

 piece of blotting or filtering paper, and is then placed in the 

 sunlight. After a short time it will turn green. Chloride of 

 silver, as obtained in a similar manner, melts into an orange- 

 red globule, which changes to clear-yellow on cooling, and 

 finally becomes white, or nearly so. Placed in sunlight it 

 rapidly assumes a dark-grey colour. Iodide of silver, under 

 similar treatment, forms whilst hot an almost black globule, 

 which becomes amethyst-red during cooling, and dingy-yellow 

 when cold. In the sunlight it retains the latter colour. A 

 mixture of chloride and iodide of silver assumes a greenish 

 tint somewhat resembling the colour acquired by the bromide 

 globule. This, however, can scarcely give rise to any error, as 

 the presence of iodine is revealed, even if no violet-coloured 

 fumes be emitted, by the dark amethystine colour of the 

 bead whilst hot. 



On the Detection of Carbonates in Blowpipe Practice. — A 



