Chemical Examination of Algerite. 121 
as a carbonate from the fact that it is at once taken up by 
hydrochloric acid with effervescence. Another portion of 
the mineral decomposed by hydrochloric acid, in Laurent's 
apparatus, gave a large portion of potash, mixed with a little 
soda ; no lithia could be detected in the alkalies. 
The quantitative analysis effected by the process above 
mentioned, gave the following results. 
Silica, . : : 49-82 contains oxygen 26-60 
Alumina, . SUO TOI 
Peroxyd of kii . 1:85 
Magnesia, . oa ES 
Potash, ; 
10:21 t 211 
Soda-traces, ; crm : 
Water, z ; mi 
Lime, 2°20 
3°94 
Carbonic acid, 1°74 : J 
| 99:45 
The composition of the mineral, deducting the carbonate 
of lime, is evidently a hydrated silicate of alumina and pot- 
ash, in which small quantities of magnesia and iron, replace 
in part the alumina and water. Representing AE (alumini- 
cum) as Al, and Fe$ (ferricum) as Fe$, we have, taking 
silica as Si O, and considering the Mg as replacing in part H 
and Fe, the following formula as very closely expressing its 
constitution, 5S1 O,4-4HO, KO, 6 $ A150, 4 FeO or 5Si O, 
+12MO, which if we take silica as Si O is evidently at once 
brought to Si, M, O, or in M. Gerhardt’s notation Si, M, O,, 
Which is one of the typical forms which M. Laurent has de- 
duced from his researches on the natural silicates. This 
requires a ratio between the oxygen of the silica and that of 
the other oxyds of 5: 4, and that of the silica being 96-60, 
theory demands for the bases 21-28 while experiment gives 
SHE: Although it will be difficult to arrange the elements 
ona in a a satisfactory manner, according to the ideas of the 
! Am. Jour. of Science, vol. iv. p. 407. 
: JOURNAL B. S, N. H, 16 DEC. 1849. 
