[ 6 54 ] 
2. Platina was digefted in a quantity of aqua regia 
infufhcient to diflolve the whole ■ and the refiduum 
diflolv’d in a frefh parcel of the menftruum. The 
two folutions, treated as above, yielded fomewhat 
different phenomena, but no tendency to a purplifh 
caft could be perceiv’d in either. The latter, which 
looked yellow from not being fully laturated, was, 
when diluted with water, almoft colourlefs. Never- 
thelels, on the addition of the tin, it became yellow 
again, then red, and at length of a dark brownifli 
red confiderably deeper than the other more faturated 
folution. On handing for fome time, it grew per- 
fectly clear, depofiting a paler, yellowifh precipitate. 
3. To determine whether platina was capable of 
preventing a fmall proportion of gold from difeover- 
ing itfelf on this trial, one drop of a folution of gold 
was let fall into feveral ounces of a folution of pla- 
tina diluted with water. On adding fome plates of 
tin, the whole became immediately of a fine purple. 
Remark. It may be proper to obferve, that in 
thefe kinds of experiments, plates of tin are far more 
eligible than the folutions of tin ufually employ’d : 
For the folutions fail of ftriking a purple colour with 
folution of pure gold, unlefs certain circumftances 
are obferv’d, which are not eafily hit upon ; but tin 
in fubflance conftantly fucceeds, and requires no par- 
ticular precaution. 
Experiment 
As gold is reviv’d from its folutions by inflammable 
fpirits, the metal gradually arifing to the furface, in 
form of a bright yellow cuticle ; 
