MEDICINAL PREPARATIONS OF GOLD. J SI 



The cause of this is not known ; but the authors ascribe it, 

 1, to the formation of a soluble triple muriate, which tak,es 

 place when the potash is poured into the solution of mu- 

 riate of gold: 2, to the excess of acid always present in this 

 muriate: 3, to the more or less caustic state of the alkali 

 employed : 4, to the greater or less quantity of this sub- 

 stance added to the muriate of gold. 



When a solution of caustic potash is poured into a Oxide of goli 

 saturated solution of gold by muriatic acid, a yellow do^l™"" 1 

 precipitate is formed*, which, when collected on a fdter, 

 does not amount to move than 40 grs of oxide from 72 grs 

 of the metal in the solution. The remaining liquid is of a triple muri- 

 a very deep colour, and contains a triple muriate of gold T !ate remdil » 

 and potash. A fresh quantity of the caustic alkali will from whj 'L" 

 cause nx> farther precipitation, unless the liquid be kept more alkaii 



several hours in a gentle heat: but in this case a new ^ e . at 



" throw dovrn 



precipitate will fall down, extremely bulk)'', and of a deeper gold apparent** 



colouv than the former, and apparently at a different iy ''* a dff ^" 



\ s J en t state oi 



degree of oxidation. Several weeks are necessary to com- oxidation. 



plete the precipitation ; and even at last a certain portion 



"of gold will remain, which must be thrown down by a slip 



of tin, if we would lose nothing. 



If the solution of gold be very acid, there will be scarce- SupeiHuom 

 ly any perceptible precipitation: and this might be ex- acidi '>' ot ttis 

 pected, as the alkali finds a sufficient quantity of free avoided. 

 acid, to form muriate of potash enough for the production 

 of the triple salt. Indeed no precipitation at all ought to 

 take place, when the solution is extremely acid: but here 

 experience does not entirely agree with therory, for a very 

 small quantity of oxide of gold is always produced. 



The causticity of the potash is of great importance; Causticity of 

 for, if the neutral carbonate be employed, no change will Por ^j! t# •■'**" 

 take place without the assistance of heat. This, expelling Action of th« 

 a considerable portion of carbonic acid gas, will alter the carbom:e - 

 colour of the solution from yellow to greenish. If it be 

 then filtered, traces of the purple oxide of gold will be 

 found; and it will effervesce with acids, having its fine 

 golden colour restored. A few drops added to a glass of 

 water will not colour it; but, if the water be acidulated, 



• It is necessary tp employ heat. 



the 



