VOL. XlVIir.]| PHILOSOPHICAL TRANSACTIONS. 499 



That the pure platina is a white metallic substance, in some small degree mal- 

 leable ; that it is nearly* as ponderous as gold, equally fixed and permanent in 

 the fire, equally indestructible by nitre, unaffected by sulphur, dissoluble by 

 hepar sulphuris. That it is not to be brought into fusion by the greatest degree 

 of fire procurable in the ordinary furnaces, whether exposed to its action in close 

 vessels, or in contact with the fiiel ; by itself, or with the addition of inflam- 

 mable, saline, vitreous or earthy fluxes. -)- 



PAPER II. 



The more obvious properties of this extraordinary mineral, and its habitus to 

 fire, singly, and in conjunction with the various substances called by the che- 

 mists fluxes, made the object of the first paper. In this, it is proposed to exa- 

 mine the effect of acid spirits, simple and compound, applied after various 

 manners ; in order to determine not only its relation or habitus to them, but 

 likewise its less obvious agreement or disagreement with the metallic bodies, 

 whose history is more known. 



The platina employed in the following experiments was previously freed from 

 its fine dust by a sieve ; from the mercury, by ignition ; and from the golden 

 and some of the other heterogeneous particles, by the eye assisted with glasses. 



Exper. 1 . — Platina with the FitrioUc Acid. 1 . Several parcels of platina 

 were digested for some hours, in a gentle heat, with spirit of vitriol, both con- 

 centrated, and diluted with different proportions of water. No solution hap- 

 pened, nor any sensible alteration, either in the liquors or the platina. 2. Three 

 ounces of well-dephlegmated spirit of vitriol were boiled with one ounce of pla- 

 tina, in a tall, narrow-necked glass, for some hours. The liquor remained 

 nearly of the same quantity as at first ; and no change could be perceived either 

 in it, or in the platina. 3. The glass being cut off a little above the liquid, the, 

 heat was gradually increased, till the liquor, which now began to evaporate, had, 

 in 5 or 6 hours, totally exhaled, and the platina become dry, and red-hot. 

 When cooled, washed with water, and exsiccated, it was found exactly of the 

 sam^ weight as at first, and its grains not divided, or apparently altered. 



Remark. — Platina appears therefore entirely to resist the vitriolic acid ; which, 

 by one or other of the above processes, dissolves or corrodes every other known 

 metallic body, except gold. 



Exper. 1. — Platina with the Marine Acid. 1. Weak and strong spirits of 

 salt being digested, separately, with -^ their weight of platina, in a gentle 



• More ponderous than gold when duly purified, its specific grarity being then 23.000; wherea* 

 that of gold is only 19.3. 



+ White arsenic excepted ; for on exposure to a sufficient degree of heat, with such an addition, it 

 may be brought into fusion. 



3s2 



