504 PHILOSOPHICAL TRANSACTIONS. [aNNO 1754. 



Exper. 6. — 1 . The spirits of sal ammoniac, prepared both by quicklime and by 

 fixed alkaline salts, added to solutions of platina diluted with distilled water, 

 precipitated a fine red sparkling powder ; which, exsiccated, and exposed to the 

 fire in an iron ladle, became blackish ; without at all fulminating, which calces 

 of gold, prepared in the same manner, do violently. On washing some of this 

 precipitate on a filter, by repeated affusions of water, the greatest part of it dis- 

 solved ; only a small quantity of a blackish matter remaining, and the liquor 

 passing through of a deep, bright, golden colour. A very large quantity of the 

 fluid was tinged of this colour by a small one of the powder. 



1. Salt of wormwood, fixed nitre, the lixivium saponarium of the Lond. 

 Pharmacopceia, precipitated a powder similar to the foregoing, except that its 

 colour was less brilliant. 



3. Sal ammoniac likewise, one of the ingredients, to which the menstruum 

 owed its power of dissolving the platina at first, precipitated great part of it in 

 form of a similar powder. 



4. The liquors remaining after all these precipitations with saline substances, 

 appeared of a yellow colour, almost as deep as before the precipitation. Fixed 

 and volatile alkalies being added alternately, the liquor still continued yellow : 

 but either of them, added after sal ammoniac had performed its office, threw 

 down a fresh precipitate, which left the liquor colourless. 



5. The addition of tin likewise, after either of the salts separately had thrown 

 down all they were capable of doing, occasioned a fresh and complete precipita- 

 tion ; provided a little more of the menstruum was dropt in, to enable the liquor 

 to act on the metal. 



Exper. 7 • As gold is totally precipitated by alkaline salts, but platina only in 

 part ; and as a minute portion of platina, remaining dissolved, tinges a surpri- 

 singly large quantity of the fluid of a yellow colour ; it was presumed, that a 

 small admixture of platina with gold might by this means be readily discoverable. 

 A few drops of a solution of platina were therefore mixed with above 100 times 

 the quantity of a solution of gold ; the whole diluted with water ; and a pure 

 alkaline salt gradually added, as long as it occasioned any effervescence or preci- 

 pitation. The remaining liquor was of so deep a yellow colour, that it was 

 judged the platina would have discovered itself, though its proportion had been 

 less than 1000th part of that of the gold. 



Exper. 8. — 1. Zinc, which totally precipitates all the other known metallic bodies, 

 put into a diluted solution of platina, was very quickly acted on, and threw 

 down a blackish calx. The liquor in good measure preserved its yellow colour ; 

 a n ark that part of the platina remained suspended. 



2. Iron, wnicn precipitates all the metals from their solutions, except zinc. 



