HISTOUY 01? GOLD. 537 



If it be placed between the eye and the light, we shall perceive, 

 by the blue tint, that the gold begins to mingle with the pur- 

 ple powder. 



The aqueous sulphuric acid likewise enlivens the purple. Sulphuric acicf. 

 because it takes from it a httletin; but its action goes no 

 farther. 



The sulphate of tin at a minimum likewise precipitates gold Sulphate «t 

 in tSie state of the purple powder of Cassius. ^'"° 



0/ Gold precipitated by some Vegetable Juices. 

 I have shown elsewhere, that there are few vegetable juices, Gold precipita- 



whether acids, gummy, saccharine, extractive, &c., which ^t^ ^^ ^**^''*^^" 

 . ' ble substances, 



have not the property of disoxidating gold ; but among the 



extractive and colouring juice^, there are several v.hich unite 



with this metal, and form with it purple lakes of a deep and Purple lakes. 



frequently very fine colour. Such unions still farther confirm 



the disposition gold has to form combinations of a particular 



order. 



If a solution of gold be poured into a very clear solution of With dragon's 

 dragon's blood, and the lake be suffered to subside, washed 

 several times in boiling water, and then dried, we shall have 

 a lake compounded of metallic and colouring matter, united 

 by actual combination. 



If 100 grains of this lake be burnt, and the ashes fused with 



a little borax, a button of gold, weighing 40 grains, will be 



produced. A hundred parts of gold, therefore, carry down loo parts of 



with them 250 parts, or twice and half its weight of colouring ™«^talh(> gold 



^ o o chemically 



matter. The following facts will show, jfirst, that the gold is combined with 



in the metallic state in this compound: and secondly, that a 250 of colour- 

 *■ •" ing prmciple. 



combmation takes place. 



Water is a solvent of the principles contained in dragon's proofs of com - 

 blood : yet water takes nothing from this auriferous lake, ^'i'^a^icn. 

 Alcohol, which dissolves dragon's blood completely, takes 

 nothing from this lake; it is not even slightly tinged by it. 

 Potash takes from it a great portion of colouring matter, but it 

 does not completely divest it of this ; for there still remains a 

 lake of a very fine purple, in which we find the gold united to 

 the colouring principle. Three applications of potash were 

 incapable of reducing the gold to its original purity. 



Vol. XIV,— August, 1806. Xx Aramo« 



