42 REPORT — 1839. 



chloric acid has. But if it be persistent as a chloride, it should be decom- 

 posed by hydrobromic acid, since the chlorine and hydrogen are com- 

 bined with two bodies, gold and bromine, for which they have a less at- 

 traction than they have for each other ; they should therefore combine to 

 form hydrochloric acid, while the relinquished gold and bromine also 

 unite that a bromide of gold may be formed. When this experiment is 

 performed, the chloride is decomposed by hydrobromic acid, the bodies 

 added being the dissolved terchloride of gold, and hydrobromic acid ; 

 the products of the change are, the similarly dissolved terbromide 

 of gold and hydrochloric acid ; and the immediate proof of such a 

 change having occurred, is the alteration of colour which succeeds the 

 mingling of the two bodies. The solution of the chloride of gold has 

 a pale yellow tint ; the bromide has a dark red hue ; any conversion, 

 therefore, of the chloride into the bromide is indicated by the colour 

 of the liquid passing from pale yellow to dark red. To determine the 

 certainty of this decomposition, the liquid was separated, either by di- 

 stillation or by agitation with sulphuric ether, into the bromide of gold 

 and hydrochloric acid, which were respectively tested and ascertained 

 to be such. 



The certainty of the decomposition having been determined, and its 

 occurence in atomic as well as in irregular proportions learned by re- 

 peated experiment, the theory of the change may now be considered. 



The salt of gold, being a terchloride, will require three proportions 

 of hydrobromic acid for its complete decomposition. On the supposi- 

 tion of its dissolving as a haloid, its decomposition will occur thus : 



Decomposition of Terchloride of Gold hy Hydrobromic Add. 



( The figures express atoms.) 



Terchloride f Gold, 1 -^ Terbromide of 



of gold, 1. \ Chlorine, 3^-^^^.^-'""'^ gold, 1. 



Hydrobromic f Bromine, 3--'^'^^---,,.^^^ Hydrochloric 

 acid, 3. \ Hydrogen, 3 /'^^''^-^acid, 3. 



Again, let the liquid be supposed to contain a muriate of gold, it will 

 be thus : 



Decomposition of Termuriate of Gold hy Hydrobromic Acid. 



rr, • X 1 Hydrochloric acid, 3 



Termuna e Iq 3 — ::^Water, 3. 



of gold, 1. j^Jl J ^^^,^^--- 



Hydrobromic 1 Hydrogen, 3 " ~~-___Terbromide of 



acid, 3. J Bromine, 3 ^~~'~~" gold, 1. 



According to the former of these views, the hydrogen of the hydro- 

 bromic acid takes chlorine from chloride of gold, so that hydrochloric 

 acid is formed ; according to the latter, hydrogen takes oxygen from 

 the oxide of gold, and water is formed ; while hydrochloric acid, pre- 

 viously in combination, is set free. 



By a reference to the diagrams it will be seen, that in each of these, 



