238 Intelligence and Miscellaneous Articles. 



below 482° Fahr., and it then yields oxygen ; it is insoluble in water, 

 and is not either dissolved or decomposed by alcohol. Hydrochloric 

 acid converts it into metallic gold which separates, and terchloride 

 of gold which dissolves ; this reaction requires a quarter of an hour 

 to complete it when the acid is cold, but at a boiling heat it occurs 

 instantaneously ; in the former case protochloride of gold is at first 

 formed, which itself afterwards decomposes by the usual reaction on 

 the contact of water, 



3( Au^Cl) = Au^CP + Au^ 



Hydriodic acid when brought into contact with protoxide of gold 

 becomes of a deep yellow colour, and deposits protiodide of gold of a 

 greenish colour. The supernatant liquor is a solution of protiodide 

 of gold in hydriodic acid. If the whole be boiled, the iodine is dis- 

 engaged in the form of violet vapours, and the gold is precipitated. 

 There is not therefore produced, under these circumstances, a per- 

 iodide of gold corresponding to the perchloride. 



Hydrobromic acid acts like hydriodic acid ; it gives when cold a 

 brown deposit of bromide and becomes of a deep colour ; if it be 

 boiled the liquor becomes quite light- coloured ; aqua regia dissolves 

 the protoxide immediately, but neither sulphuric, nitric, nor acetic 

 acid has any action upon it ; potash and soda dissolve it only when 

 in the nascent state ; ammonia forms a violet fulminating compound ; 

 if rubbed with a hard body it explodes ; but detonation is not so loud 

 as that of the fulminating gold obtained with the teroxide of gold ; 

 hydrogen gas easily reduces it when hot, but without any sensible 

 phsenomenon. 



Protoxide of gold ought to be arranged with indifferent chemical 

 compounds, since it is capable of combining both with acids and 

 bases ; thus, while potash dissolves it in the nascent state (for ex- 

 ample, during the treatment of the protochloride with this alkali) 

 we shall find, on the other hand, that stannic acid readily combines 

 with it. 



The extraordinary changeableness which Berzelius supposed to 

 be a property of this protoxide, does not belong to it. It is in fact 

 much less alterable than the teroxide of gold, which is a usual cir- 

 cumstance, for the first degree of oxidizement of a metal is in general 

 more stable than the subsequent. Thus the protoxide of gold does 

 not decompose below 482° Fahr., whilst the teroxide undergoes it at 

 437°. 



Direct light, which reduces the teroxide of gold after a certain 

 time, has no action on the protoxide ; there are, moreover, a great 

 number of chemical agents which easily reduce the teroxide of gold, 

 that have no action whatever on the protoxide ; such for example 

 are tartaric acid, acetic acid and alcohol. 



When protoxide of gold has been dried, it is perfectly insoluble in 

 water ; but if at the moment of its preparation it be put into contact 

 with distilled water, there is then produced what is called apparent 

 solution ; thus when an attempt is made to wash on a filter the prot- 

 oxide obtained from the protochloride of gold by potash, it may be 

 observed that a small portion of the product is carried off by the 

 washing water, which passes through of a deep violet-blue colour, 



