l 597 1

part is extracted pure by powdering and digesting them inwater. Though it might be suspected that this salt, invirtue of its containing not only the mineral but a portionof vegetable alcali, would precipitate part of the platina aswell as gold, I could not find that solution of platina suf-fered the least alteration from it, any more than from thenative or marine alcalies.

How far these salts may suffice, for the perfect separationof platina and gold that have been intimately combinedwith one another by fusion, I have not yet had directexperience. But it may be proper to observe, thatthough both the native alcali and bariglia are supposed ge-nerally to contain some sea salt in its whole substance,which for some purposes renders them unfit, yet this saltdoes not appear to be here of any disadvantage, for puresea salt occasioned no precipitation or turbidness in a solu-tion of platina, any more than in solution of gold. Theplatina employed in these experiments was such as hadbeen cupelled with lead and urged afterwards with repeatedstrong fires, page 570.

IV. Precipitation by sal ammoniac.

T he alcaline salts in the two foregoing articles precipitatethe gold, and leave the platina wholly or partially dissolvedin the liquor. Sal ammoniac has a contrary effect, preci-pitating great part of the platina, and leaving all the golddissolved; and on this principle platina may be discoveredin gold as readily and as effectually as on the other. Themetal being dissolved in aqua regia, add a little solution ofsal ammoniac made in water: if the gold contained anyplatina, the liquor will instantly grow turbid, and a fineyellow or reddish precipitate will quickly fall to the bot-tom : if the gold was pure, no precipitation or change oftransparency will ensue.

H h h h 2

V. Sep a-