in Porcelain Painting . 143 
is slowly brought to a red heat in a s;lass retort. As the, 
volatile neutral salt, combined with the platina in this 
precipitate, becomes sublimated, the metallic part re- 
mains behind in the form of a gray soft powder. This 
powder is then subjected to the same process as gold; 
that is to say, it is mixed with a small quantity of 
the same flux as that used for gold, and being ground 
with oil of spike is applied with a brush to the porce- 
lain ; after which it is burnt in under the muffle of an 
enamelier’s furnace, and then polished with a burnishing 
tool. 
The colour of platina burnt into porcelain in this 
manner is a silver white, inclining a little to a steel gray. 
If the platina be mixed in different proportions with 
gold, different shades of colour may be obtained ; the 
gradations of which may be numbered from the white 
colour of unmixed platina to the yellow colour of gold. 
Platina is capable of receiving a considerable addition 
of gold before the transition from the white colour to 
yellow is perceptible. Thus, for example, in a mixture 
of four parts of gold and one of platina, no signs of the 
gold were to be observed, and the white colour could 
scarcely be distinguished from that of unmixed plati- 
na : it was only when eight parts of gold to one of platina 
were employed that the gold colour assumed the supe- 
riority. 
I tried, in the like manner, different mixtures of plati- 
na and silver; but the colour produced was dull, and did 
not seem proper for painting on porcelain. 
Besides this method of burning-in platina in sub- 
stance on porcelain, it may be employed also in its dis- 
solved state; in which case it gives a different result 
both in its colour and splendour. The solution of it 
in aqua regia is evaporated, and the thickened resi- 
duum is then applied several times in succession to 
