ALL
A L O
( 44: )
ALLAN1TE.*
This mineral occurs in oblique tetrahedralprisms, the alternate angles of which measure117° and 63, or in compressed hexahcdralprisms terminated by tetrahedral summits; italso occurs uncrystallized and then is eithermassive or disseminated being mixed with blackmica and felspar. Its specific gravity as far ascan be ascertained on account of the intimatelyintermixed mica, is between 3.1 and 4.0. Itscolour is brownish-black; when bruised darkgreenish grey. Externally it is dull. Internallyit exhibits a small conchoidal fracture with ashining lustre between resinous and metallic.It is opake, in hardness ranks between felsparand glass ; is brittle and easily frangible. Be-fore the blow-pipe it froths and melts into abrown slag. It gelatinizes in nitric acid, andloses about 4 per cent, of its weight by strongignition.
The substances obtained from 100 parts ofit on analysis by Dr. Thomson, are
35.4 silex9.2 lime4.1 alumine
25.4 per-oxkle of iron
33.9 oxide of cerium
4.0 volatile matter
112.0
Allanite is a native of Greenland , but of itsgeological history we are as yet entirely ignorant.
ALLOCHROITE. b Splittriger GranatK.
The colour of this mineral is yellowish orbrownish-grey. It occurs in opake amorphousmasses. Its fracture is uneven passing to splin-tery, with a slight degree of lustre. It givessparks with steel, and is difficultly frangible.Sp. gr. 3.5. Before the blow-pipe it is fusiblewithout addition into a black shining opakeenamel.
It has been analysed both by Vauquelin andRose, with the following results :
V.
35.
30.5
8 .
17.
3.5
6 .
R.
37. silex30. lime5. alumine
18.5 oxide of iron6,25 oxide of manganese0. carbonate of lime
100.0 96.75
This mineral is considered by Karsten as avariety of garnet, and in fact its analysis nearlycoincides with that of melaruta or black garnet.
It occurs generally in pieces covered by car-bonate of lime, and by dodecahedral crystalswhich appear to be garnet. These dodecahe-drons are implanted by their Ijvs'er extremitiesin the allochroite, into the substance of whichthey appear to pass by insensible degrees. Thecarbonate of lime in Vauquelin’s analysis is nodoubt foreign to the composition of this mineraland is to be attributed to the calcareous sparwith which it is mixed.
It occurs in the iron mine of Virums, near'Drammen in Norway .
Three analyses have been made of thissubstance, of which the following is an abstract.
The first we shall mention is that of M.Braconnot. c
Aloes is a dark brown semi-transparent ex-tract, easily reduced to powder, and very bitter,prepared from the natural juice of severalspecies of the aloe plant, either by natural orartificial heat. The finest species is preparedonly by inspissation in the sun’s heat. Thefinest sort was selected for the following ex-periments :
50 grammes were heated per se in a retort,with a heat at first vety gentle, and afterwardsincreased. The first product was a waterloaded with the flavour of aloes, then a colour-less water holding some acetous acid but noammonia: then a red oil soluble in alcohol;and then at a higher heat much carburettedhydrogen with oil. The coal contained nopotash.
Aloes rubbed in a mortar with water pro-duces a viscous mass like turpentine whenpressed with the fingers. A large quantity ofwater however dissolves the whole, exceptinga little woody impurity, and the solution ofthe last portion is as bitter as the first. Byheating the water, the solubility of aloes isgreatly increased, and the hot saturated solu-tion will assume somewhat of a crystalline formby cooling. The watery solution of aloes red-dens litmus. Its colour is rendered deeperby lime-water and the alkalies, but nothing isprecipitated. Goulard’s extract produces adeep precipitate, and the supernatant liquor be-comes colourless.
The watery solution when long exposed tothe air becomes mouldy, and then gives anabundant precipitate with gall-nut, but when
* Hauy Tab. Comp. 57.
a Nich. Journ. Jtxix. 48.
* An. Chim. Tom. 68,