Because I don't have Platinum metal on hand I’m forced to make an alloy of Lead metal and a 99.9% Platinum Chloride (PtCl) standard.
To accomplish this task I begin by cutting a 1 gram piece of 99.5% Lead from a small bar, which is hammered thin and flat. Then I curl up the outside edges to make what I refer to as a boat, as seen in the below image.

This image is showing the pipett dispensing a total of 2 ml of liquid platinum chloride into the Lead metal boat.
Each milliliter is supposed to equal 1 mg of Pt.
I suspect that some Pt will be volatilized as the propane torch heats the liquid.
No metal odor was detected as I drove off the liquid, but could certainly smell the chlorine.
Some caution is necessary to avoid melting the thin Lead edges and thus losing liquid.
When all the liquid has been dried the thin Lead is folded in half and folded again and again as shown below. Then this metal that now contains the residue from the liquid is hammered to somewhat seal-in this reside, so that when the lead is melted it will alloy with the Pt.

These above images are the melting and alloying (Pb & Pt) of the folded Lead metal boat.
Although these images are taken during the hot stage and will be significantly different when the plaster tablet has cooled they nevertheless provide sublimates of this heat range and potential alloy that when compared to Lead alone will be slightly different and as a result will provide valuable clues for future reference.

10x
This image shows the resultant cooled PbPt alloyed button from the above plaster images.
Colors are very close to accurate, excepting shadows and reflective light source.
The reddish feathery glob on top of button is Lead oxide (Pb3O4) that forms easily when using a heat source (propane torch) that blows considerable amounts of air, which will allow oxidation of the molten lead.
Direction of torch flame is from right to left.
This button was removed, reasonably cleaned of adhering plaster and minor slag and cupelled as shown in following images.

The yellow color is the sublimate of Lead oxide.
This and the following images attempt to demonstrate a simple cupellation procedure that anyone can do after a little practice. Thus, there is no immediate need of having expensive electric/gas furnaces to accomplish the normal laboratory setting and task of obtaining precious metal prills from cupelling lead buttons of any size.
For those who may decide to learn to cupel with this method should notice the position of intense heat, which is below the molten lead button. I gradually heat the cupel with the Lead button already in place (within the cavity). so that the lead melts only when the bone ash below the lead button is sufficiently hot enough to begin absorbing the molten Lead.
Furthermore, too much heat (flame and force) directed at the bead will vaporize considerable amounts of the precious metals, as well as allow the cupel to cool below the heat range of absorption, causing the button to freeze.
Prior to melting the Lead button I place a piece of silver under the lead so that the lead will absorb the silver and usually act as a collector of sought for precious metals.

The completed cupellation resulting in the precious metal silver prill.
As can be seen with this cooled cupel the colors have significantly changed and there is a brownish stain within the cavity that contains the prill. This brownish color is volatilized silver. Personally, I’d rather have this occur than not, because when I don’t see this dark stain I am suspicious that considerable amounts of Lead and other potential undesirable contaminates could be hiding within the silver prill.

10x
Colors are being influenced by the cupel stains.
The image shows the alloyed silver prill resting inside the cavity I previously dug out of the cupel to contain the original Lead button.
Although most of the molten lead is absorbed into the bone ash cupel a small amount is also vaporized and can be seen a wisp of smoke during the entire cupellation of the lead button till near the end of the procedure.
I always save the used cupels if they have not been totally saturated with Lead and whatever contaminates the Lead may contain. Usually, when I begin to re-use and previously used cupel I scrape away any obvious contamination from the surfaces and only place the new lead button on/in clean areas to conduct tests like this, thus avoiding using new cupels. As long as there is a sufficient amount of uncontaminated cupel surface and the cupel does not crumble into a mess while scraping a new surface and cavity for the Lead bead to be cupelled within then small tests like this one works quite well.
Conducting cupellations like this will cause an unavoidable loss of some silver and possibly other precious metals. However, it is a quick and inexpensive way to make reasonably accurate tests without having to resort to relying upon laboratory expertise.
Furthermore, if the prospector does not learn how to do simple tests then the prospector will remain at the mercy of those who capitalize upon the prospectors ignorance.
Notice the crack below the prill. Cracks can be a source of considerable loss.

30x
Obviously this is not a pure silver prill due to the surface irregularities.
This is one of the primary reasons for conducting tests like this so a prospector can learn to distinguish abnormalities of silver prills.

40x
This higher magnified view of the PtAg prill more clearly shows crystalline structure of this type of alloy and should be of significant aid in helping to make educated guesses as to what some precious metal prills might contain.
Because of the curved surface only a portion of this spheroid could be focused.
Color of bead is actually much whiter, but the surrounding cupel colors are masking the whiteness.
Naturally I keep all cupelled beads so I can conduct additional tests. Such as dissolving them in water/nitric acid baths and the utilization of chemicals to confirm or deny the presence of other precious metals within the silver.

1-01-07
Re-melted prill on cupel to be assured that no lead remained..
Size of prill = .07” or approximately 26+ mg or 26+ ounces to the ton.

40x
This image illustrates a more pronounced and unique crystal structure
3:15PM placed this prill in a glass slide-well and added 4 drops water & 1 drop nitric acid. Immediate reaction began, but quickly slowed down to almost no action at all.

40x
The bottom of prill v/s top that protruded out of the acid water has digested surface silver exposing the Pt and showing a distinct crystalline structure, especially when viewed on a full monitor screen.
Had to add heat to get the acidic water to begin digestion of prill.

40x
The blackish ring around base of prill is the unfocused bubbles generated by nitric acid with a little heat
3:30PM

40x
Prill covered in slick coat of solid black and black fragments being thrown off the prill and beginning to litter the glass slide.

40x
Same image as above, but focusing on the tiny black particles resting on slide that has peeled off.
There is the slight odor of coffee, but not the same as the Rh.

70x
Prill completely digested, leaving a black pile of definable black metal crystals (sponge).
Because this large mass of blacks does not allow discriminating visual clarity I focused on the outer perimeter/periphery of the pregnant acidic solution.
These tiny blacks have no disenable crystal structure at this magnification, and higher magnification only seems to produce a worse image.