1822.] Mr. R. Phillips on certain Substances, &c. 53 
ArtTicLE XII. 
~ Qbservations on certain Substances which have been supposed to 
act as Acids, and as Alkalies. By R. Phillips, FRS. L&E, 
Xe. 
Tue first volume of the Annales de Chimie contains a 
memoir by M. Perthollet; the object of which is to show, 
that if the metals, when oxidized, perform the functions of 
alkalies with the acids, the same oxides also act as acids with 
the alkalies. Mr. Smithson (Phil. Trans. 1811,) adopting a 
similar opinion with respect to the action of silica upon other 
earths, has considered it as an acid, and has employed the term 
silicate to express its compounds: thus he says that zeolite 
may be regarded as a silicate of alumina and soda; and he 
considers the compound as bearing some analogy to alum. 
/M. Berzelius has not only admitted that silica performs the part 
of an acid in certain compounds, but has attributed similar 
powers to alumina, and employs the term aluminate. The fol- 
lowing passage from his Nouveau Systeme Minéralogique (p. 76), 
would however appear to indicate that he had not clearly de- 
termined the nature of the substances included in this class : 
“ Selon Ekeberg, le gahnite contient 
Alumine ........ 60°00 2 contenant §28°2 12 ou 6 
Oxide de zinc.... 24:25§ oxigéne 4-0 2 1 
Oxide de fer ... beg.bg comme oxidule 2:0 ] 
POLL, as wens 4:75 3-3 1 
On peut considérer ce minéral de plusieurs manicres. Si nous 
ne faisons pas attention au fer et a la silice, ce sera un alwmi- 
nias zincicus, dans lequel l’alumine contient six fois l’oxigéne 
de l’oxide de zinc, 21 A%, et qui peut etre coloré par le 
silicias ferrosus. D’un autre cété il peut encore tre composé 
d’un double aluminiate de zinc et de fer, c’est-da-dire former un 
trialuminias ferroso-zincicus, de sorte que l’alumine dans toutes 
ces combinaisons simples, contient trois fois autant d’oxigéne que 
le corps avec lequel elle se trouve combinée. Dans ce cas, 
la composition serait f A? + 227A? 4A° 8.” 
Dr. Thomson, in his System of Chemistry, has also adopted 
the idea of the action of silica as an acid; and when the au- 
thorities by which this opinion is sanctioned are considered, 
it will, Iam apprehensive, appear useless for me to endeavour 
to show, that by admitting silica and alumina tobe, or to perform 
the functions of acids, we are in danger not only of adopting 
a loose system of nomenclature, but also of attributing to bodies 
