How to precipitate Chloroplatinic acid? For the precipitation reaction, I have to react $\ce{H2PtCl6}$ with $\ce{(NH4)2CO3}$ while maintaining the $\ce{pH}$ in the range of 7-8 at 60 °C. But the problem is Chloroplatinic acid is not precipitating. Instead, the acid evaporated by making holes in the aluminium foil which were not present before.
Can you please point out what I'm doing wrong?

Theoretical reaction:

$$\ce{(NH4)2CO3 (aq) + H2PtCl6 (aq) -&gt; (NH4)2PtCl6 (s) + H2O (aq) + CO2 (g)}$$

PS: Aluminium foil was just used for proper heating
I suspect that you could be forming an aqueous solution of $\ce{(NH4)2PtCl6}$.

I would like to make an observation as a person who has done platinum group metal chemistry, the anionic chloro complexes of PGMs like $\ce{PdCl4^2-}$ and $\ce{PtCl4^2-}$ are very toxic. They can induce a nasty allergy to PGMs. I would suggest that you do not work at home with these substances.

Also in my experience at least with $\ce{PdCl4^2-}$, I have always found that if you want to bring it out of solution then cation methathesis with a potassium salt can bring the substance out of solution as a brown solid. I suspect for the hobby chemist that low sodium salt would be the best reagent for doing this transformation.

For the lab chemist I would suggest using tetramethyl ammonium chloride or even tetraphenyl phosphonium chloride