1822.] are supposed to act as Acids and as Alkalies. 55 
alkali, that Mr. South has discovered, it possesses the power of 
turning turmeric paper brown. Again, Mr. Faraday informs me, 
that by boiling the solution of muriate of zinc, as usually ob- 
tained, with an additional quantity either of the metal or the 
oxide, a solution is produced, which acts on turmeric paper as 
an alkali. There cannot, therefore, be any doubt as to the power 
of oxide of lead and of oxide of zinc, to perform the function of 
an alkaline base. 
The property which oxide of lead possesses of combining with 
the alkalies, potash and scda, or in other words, performing the 
function of an acid, is as perfect as that of silica ; and it resembles 
alumina in forming a crystalline, and consequently a definite com- 
pound with an alkaline base. M. Berthollet, in the memoiralready 
alluded to, states that when oxide of lead is boiled with lime 
water, very small iridescent and transparent crystals are formed. 
Now this compound is the more remarkable, because it results 
from the combination of two bodies, which possess distinctly 
marked alkaline properties. ‘Similar observations may be made 
with regard to oxide of zinc ; it combines with ammonia, potash, 
soda, and lime, and therefore appears to perform the functions 
ofan acid even more extensively than oxide of lead. 
The powder of Cassius is a compound which it would be dif- 
ficult to describe, on the assumption that its formation depends 
upon the acid nature of one, and the alkaline nature of the other 
constituent. In fulminating gold, the metallic oxide appears to 
act as anacid, for itis incombination with ammonia; but with 
the acids, the oxide of gold performs the function of a base, 
giving rise to the well-known salts of gold. Oxide of tin seems 
in some compounds to act as an acid ; thus it combines with the 
alkalies, potash and soda; and italso exhibits distinctly the proper- 
ties of an alkali, as far as combining with acids is to be esteemed 
as such. If, however, the powder of Cassius be a compound 
of oxide of gold and oxide of tin, as is generally allowed, what 
functions can be attributed to them? Do they combine as 
acids, as is supposed to be the case, when the fluosilicic acid is 
formed ? or do they combine as alkalies, as when lime and oxide 
of lead unite? orif we consider one oxide as performing the 
- function of an acid, and the other that of an alkali, what rule 
have we for assigning to each its peculiar office? These 
remarks might be extended to a greater length, especially if 
the oxides of antimony were taken into the account: these 
have been supposed by Berzelius to act the part of acids, 
and he has accordingly adopted the appellations of antimoniates 
and antimomtes. There are many cases also in which metallic 
oxides combine with vegetable products, such as oxide of 
lead with gum, starch, &c.: now in these cases, the rules of 
nomenclature have been so completely set at defiance, and 
chemical propriety so violated, as to give these compounds the 
appellations of gummate and amylate of lead. Are we then to 
