837 
some of the Substances which accompany it, See. 
Theory would certainly give a general preference to platina, 
from its resistance both to heat and to acids ; and practice will 
justify this preference, in all but a single instance. If a quantity 
of potash be kept for some time in fusion, in a platina crucible, 
it will be found that the crucible has lost several grains of its 
weight. The platina so dissolved may be looked for in the pot- 
ash ; and, if this be saturated with muriatic acid, and evaporated, 
we shall find the well-known triple salt, formed by the combi- 
nation of muriatic acid with potash and oxide of platina. This 
action of potash upon platina, does not depend upon any me- 
chanical cause, such as friction, the force that determines it being 
purely chemical. If a salt formed by potash, or a salt formed 
by ammonia, be mixed with a salt of platina, a precipitate en- 
sues, which is a triple salt ; and it is by this method, that the 
Spanish government detects the platina, in the ingots of gold 
sent from their American possessions. It is therefore evident, 
that an affinity does exist between potash and platina, in a cer- 
tain state ; and I imagine it to be this affinity, which causes the 
©xidizement of the platina, when potash is kept in fusion upon 
that metal. I must however observe, that my crucible was 
prepared by Janetty, in Paris, according to a method he 
has published in the Annales de Chimie ; and that he always 
employs arsenic, a little of which certainly remains united 
to the platina. What influence arsenic may have, remains to be 
determined. Soda does not form a triple salt with the oxide of 
platina for I have frequently kept this alkali in. fusion, in, a 
platina crucible, for a long time ; yet very little action was pro- 
duced upon the metal. This fact seems to corroborate my 
assertion, that the affinity of potash for oxide of platina, deter- 
mines the oxidizement of the metal. 
