186 —§ On the Combination of Silicium with Platina, 
The platina in the plain crucible did not melt; it only ac- 
quired a greater lustre. That in the charcoal crucible was com- 
pletely melted into a button. 
These experiments. were repeated several times, and always 
with similar results ; and the metal was fused much more readily 
when covered with charcoal powder. | ' 
It was perceived, that the melted platina gained a small in- 
crease of weight in the process, showing its combination with 
some substance, which was naturally concluded to be charcoal, 
since it was every where in. contact with this body. 
The melted platina exhibits the following properties: Its 
aspect is greyish-white ; it is with difficulty cut with a knife, 
does not easily yield to the file; its specific gravity is 20°5. In 
the cold it flattens a little under the hammer, but it soon cracks 
and presents a granulated fracture. When hammered at a cherry- 
red heat it becomes grained; at a very low red it slightly flat- 
tens, and then cracks. — It does not in any degree alter its tem- 
per by heating and gradual cooling. Exposed to the blast of a 
forge-furnace, it was not even softened. As this method was 
not sufficient to drive off the supposed carbon in its composition, 
it was cemented for an hour with oxide of manganese ; but the 
button of platina lost none of its properties, and remained equally 
refractory; and I then began to doubt of the presence of carbon, 
which I had taken for granted. It was, therefore, important to 
examine whether platina would, like iron, combine with char- 
coal by cementation. For this purpose I stratified slips of platina 
with powder of wood-charcoal in a crucible, which was heated 
very strongly for four hours, but to a degree short of the melting 
point of platina thus circumstanced. On examination, the platina 
was found to have lost part of its lustre, and its surface presented 
small inequalities, like blistered steel. Its specific gravity was 
from 17:5 to 18. It acquired in the process a considerable 
hardness, so as easily to scratch pure platina, and even iron, but 
not steel. Its hardness was not increased by quenching in cold 
water. It had gained by cementation, as well as by fusion, a 
small increase of weight. Perhaps this process might be of some 
use in the arts, either in cutlery, or particularly in gun- making, 
where the softness of common platina is complained of. 
Examination of the melted and cemented Platina, 
Eighty grammes of this platina were treated with aqua-regia, 
The solution was more difficult than with pure platina. No trace 
of carbonaceous residue appeared during solution; but, as it pro- 
ceeded, there was observed a transparent jelly, which covered. 
the bits of platina, and rendered the solution more difficult. By 
long digestion and much shaking, the whole, or nearly so, was 
dissolved ; 
