ON PLATINA, 119 



nous fand, one of which is obedient to the magnet, and an- 

 other which is not attracted by the magnet, and which is only 

 partially adted on by acids, I fliall ("ay no more in this place The ferruglnousi 



concerning thefe bodies but (hat the firft contains titanium and 'f"'^' ""'^'^ 

 o ' 11 in UiTi and 



the fecond chromic acid, in confiderable quantity. chromic acid. 



The beft method to free platina of commerce from thefe ad- Mechanical 

 mixtures, is that recommended by Prouft, which con lifts in F"[,'^^^*^'°" ^ 

 fpreading out the platina on a fheet of paper, and carefully 

 blowing away the lighter parts by means of a pair of bellows. 



Platina thus purified I introduced into a porcelain retort, to Crude platina by 

 which a g^lafs receiver had been fitted, previoufly filled one- ^ioV"ffords'a*" 

 third full of water. After having placed the retort in a re- blue fublimate 

 verberatory furnace, I raifed the fire gradually, and increafed ^°'"'*^'^ '" ^^^"* 

 the heat to the utmoft I could produce, which was kept up for 

 two hours. Nothing particular attended this procefs, except 

 that the water with which the receiver had been partly filled, 

 acquired a greenidi hue towards the end of the procefs. On 

 the roof of the retort, a fine blue powder was fublimed, of 

 which I fliall fay no more at prefent than that it was foluble in 

 water. The water in the receiver, after having been fufl^ered 

 to ftand for a few days, had acquired a beautiful blue colour, 

 which furpafled the colour of the beft^ ultramarine. 



It was impoffible to get the platina out of the retort. On The platina 

 breaking the diftillatory veflTel, the metal was found aglutinated, f"|"!:*"^ 

 the upper furface of the mafs had a rufty appearance, the 

 middle wa§ lefs difcoloured, and the lower part had lufl^ered 

 no perceptible change. 



In order (o examine the colouring matter which tinged the The aqueous' 

 water of the receiver, I dropt into it a folution of an alcali; biu"^ matter af! 

 this produced inftantly a blue precipitate. Sulphuric and mu- forded a precipi^ 

 riatic acids, when mingled with this fluid, occafioned no jHabitudeTw'th 

 change. Nitric and oxiginized muriatic acids changed this icjds, &c. 

 blue fluid, firft to a lilac, but it foon loft this colour, and the 

 whole became limpid. Water holding in folution fulphuretted 

 hydrogen gas, occafioned no precipitate; but hidro-fulphqret 

 of ammonia threw down a grey precipitate, which became 

 blue by the afFufion of acids, and then was rendered foluble 

 again in hidro-fulphuret of ammonia. 



A fmall quantity of the blue precipitate colle6ied froin thq The blue fubll- 

 roof of the retort, when 'urged with the blow-pipe in con- ^^f^g j]^^''^,^^^^ 

 aft with borax, imparted no colour to this fait. When heated P'PeJ it ^'^^ not 

 perfe, it difappeared cempletely, *°'°"'" *!''"*• 



Having 



