on different Combinations of Fluoric Add . 361 
cubic inches of silicated fluoric gas, and 60 of volatile alkali 
(barom. 30, therm. 60) in a small glass jar over mercury, 
being carefully collected and introduced into water, afforded 
five grains of pure silex, weighed after being well washed and 
heated to redness. 
The saline solution, since part of the silex of the silicated 
fluoric acid gas is separated during its production, appears to 
be a subsilicated fluat, or a combination of subsilicated fluoric 
acid and ammonia. Another mode of making it, more directly 
proves that this is its composition. When ammonia is added 
to the subsilicated fluoric acid in excess, this salt is formed 
without any precipitation. From these facts, it may be con- 
cluded, that independent of water, which appears to be essen- 
tial to its existence, 100 parts of it consist of 
28.34 ammonia 
71.66 acid 
100.00 
Subsilicated fluat of ammonia has a pungent saline taste. It 
just perceptibly reddens litmus paper. Slowly evaporated, it 
forms small transparent and brilliant crystals. The largest I 
could obtain, appeared to be tetrahedral prisms. The solid salt 
is very soluble in water ; but is not deliquescent. When heated 
it appears to sublime unaltered. It is curious that the solution 
of this salt, when evaporated by a heat near its boiling point, 
powerfully erodes the glass or porcelain vessel, and a residuum 
of silex appears, on the addition of water, to redissolve the salt. 
This erosion and residue of silex I have seen produced three 
times following, with the same quantity of salt. I mention the 
fact, which, I believe, was before observed by Scheele, without 
