MEDICINAL PREPARATIONS OF GOLD. 133 



removed. When this ceases to be reproduced, the liquor is 

 to be filtered, and the precipitate washed in distilled water, 

 dried in the shade, and powdered. This is the purple powder 

 ofCassius. 



If the oxide of gold be precipitated by a solution of tin, it Precipitate 

 is of importance, that the tin be in a fixed state of oxidation, of tin< 

 otherwise the product will vary both in its nature and quan- 

 tity. A uniform solution may always be obtained by dissolve Preparation of 

 ing slips of tin in muriatic acid at 12° [l'089], filtering, eva- the solution, 

 porating to the point of crystallization, dissolving the crystals 

 in pure water, and filtering again. Part of this solution 

 should immediately be mixed with the liquid muriate of 

 gold ; and the union of the two salts produces a precipitate, 

 which should be increased by adding fresh quantities of the 

 muriate of tin, as long as any thing is thrown down; after 

 which the precipitate is to be washed, dried, and powdered. 

 The quantity obtained appears to depend on the quantity of 

 water added to the solutions of gold and tin. The more they 

 are diluted, the more tin is thrown down. One drachm of 

 gold, the solution of which was mixed with ten quarts of 

 water, mixed with a very ddute solution of tin, yielded near 

 five drachms and half of a very fine purple precipitate. 



It does not appear to be a matter of indifference which of Difference be- 

 these two precipitations is used. When metallic tin is em- tween . tne two 

 ployed, the precipitate is brown ; and the gold, if not in the 

 metallic state, is nearly approaching it. On the contrary, 

 the precipitate produced by muriate of tin at a minimum of 

 oxidation is of a deep purple colour; and, though jt contains 

 a little metallic gold, has much more of the oxides of gold 

 and of tin ; whence, it is obvious, the efficacy of the two pre- 

 parations cannot be the same. 



The muriate of gold is so greedy of moisture, fhat it soon Muriate of 

 deliquesces, whence it can be employed only in the liquid xeTy . 

 state; and, as its great causticity renders even this difficult, 

 Dr.Chrestien thought of uniting it with the muriate of soda; 

 •thus producing a triple muriate, less deliquescent, and less 

 caustic. 



For this purpose a solution of muriate of gold in distilled Triple muriate 

 water, obtained as described above, is to be employed ; and °*" & olu an< * 

 it is particularly important, that this salt has not an excess of 



acid. 



