DOI Seite / Zitierlink:
https://doi.org/10.11588/diglit.1327#0320
32,2
THE CRYSTAL PALACE AND ITS CONTENTS;
CRYSTALLISED SALTS. ~^^
_A_M01SrGST tlio various objects belonging to the Chemical Depart
none wcro ontitlod to a larger share of attention than the' v"'^'
Crystallised Salts, so valuable in their application to ni^nftust^118
processes. "-
First amongst these wa must mention the various largo and very beaut'r
specimens of the hydrated double sulphates of alumina and pptasli
ammonia, usually known by the name of common alum. This Bui'■■■■'-':
is sometimes discovevcel in a natural or native state ; ami wjiere ,
it occurs in volcanic districts in the form of a white flocculent powder
"™ermg the surface of lava and other trachytie bodies abounding ii Cr'
localities. In this form it occur
Sicily, and the vole
islands
l such
the south of France !,,
■them coasts ; but more piirtierda■)■'■
in the Grotto, di Ahnne on Capo Misenn
e lot ihtic it is colh ed I | ,
red-to deposit the earthy impurities ]lc]j
n'dcr to crystallise tlie alum which it con-
subsequently purified by repeated cm in).
revy minute
CAKBELMilUJJf.—BY MR. WEBB,
The candelabrum exhibited by Mr. Webb, of Bond-street, displayed great
merit, both in design and execution; stylo, that of the Venetian of the
sixteenth century. The cawing is bold" and effective, and the or-molu
branches are well arranged and beautifully chiscllod,
WAKDHOItl;.—by WII.KlXSOJf.
'fins wardrobe, in walnut-tree wood and pollard oak, is remarkable for its
good taste in the design, and simplicity in tho o mum en tat ion. It is not
ofteu wo meet with a work so uiieKueptiouaV.lv well linishej. with so little
attempt at meretricious display. (See p. 32S.)
tains. The salt thus procure
lisations. and, when brought into (he market, contains but a
amount of foreign matters. No fuel is used for the evaporation but the
natural volcanic boat of the soil in which the leaden pans are imbedded.
The alum thus obtained forms, however, but a very small proportion of
that which is annually employed in the arts; and much larger qiumti;:v;
are prepared in various localities by the chemical treatment of a niineiJ.
known by the name of alum-stono or alum-rock. This is a massive!
granular, partially crystallised, transparent, and not homogeneous rack'
which frequently enclose? quartz, sometimes iron pyrites and n 1 ancc:■;■*'■
ore. This mineral, which is a basic sulphate of alumina united with bu£
phatc of potash, is of a yellowish colour, sometime pas--:ug ;i:l> green or
brown, and is not unfrcquently found in the form of distinct crystals. Tho
ordinary alum-rock, although less pure than tho crystallised varieties, ha*
a nearly similar composition, and occurs in considerable - ::auvi-ie>. aiul m
a massive state, at Tolfa, near Civita Yccchia, in tho Papal States: a*
Montione, in the dukedom of Piombiuo ; in the Comitate of ISeregh ami
Zemplin, in Hungary; at Moht-d'Or, in France ; and in some of the islands
of tlie Greek Archipelago.
Alum is prepared from this substance by first burning the stones in
heaps or furnaces, and then transferring the residue to large wailed cistern-,
where it is repeatedly moistened will: water, and allowed to crumble j'w
three or four months; at the expiration of which Lime it is converted iiib
a, soft mud, tasting perceptibly of alum, which is subsequently washed out
with water and made to crystallise by the slow evaporation of the liquors.
Tho alum so obtained possesses most of the properties of ordinary seh:=:
alum, which will presently be described, but it has also certain distinct
characters, by which it may be distinguished from the latter salt.
The Roman alum always crystallises in opaque cubes, whereas tho
common variety assumes tho form of transparent octahedrons. It also
appears to contain a larger percentage of alumina than enters into die
composition of common alum ; for although perfectly soluble in pure water,
a deposit of that earth is determined by heating the solution to about
!U0 degrees Fahrenheit. The salt thus obtained is, however, of peculiar
value as a mordant for the purpose of lining colours, and as =ueh it is laiveiy
employed and much esteemed by the dyers of calico and other tc-xine tabfie-.
Originally the whole of tho alum consumed in Europe was produced nem
. alum-stone at Roeca, now called Edessa, in Syria—hence the name ''roc-
alum"-— and Was brought from the Levant to this and other European
: countries. About the year I-kiO the art of preparing alum was introduce:.!
! at Toll'a by Jolumn do Castro, who first discovered the alum-stone in ";■'■'
j district. Tho art spread from thence in various directions, and in m
| seventeenth century the manufacture of this substance was Qonunencw
both in this country and Germany, although tho materials used and tnc
I processes of preparing the salt wore very different from those previously
. employed for this purpose!
The greater portion of the alum at present consumed in the arts is aHHW
; from alum shale, which is a kind of clay slate impregnated with sulpinc'c-
I of iron and bituminous matters. This mineral is ton
! peninsula, in Bohemia, in the Harta, in Upper Bavaria, in Yoigtluud, ju L|:c
' mountainous districts of the Lower Rhine, near Whitby, in England, and °
I Hnrletand Campsie, near Glasgow. ...
When tiiese schists arc exposed to a high temperature, in contact »"a
air, the iron pyrites (or bi-sulphuret of iron) which they contain loses y:.»
one-half of its sulphur, and is converted into tlie simple sulphuret ot bi-
metal; which, speedily absorbing oxygon from the atmosphere, eecee;^
converted into sulphate of iron, or green vitriol. Th
transfers its acid to the clay with which it is mixed can ing hi 'tl
of sulphate of alumina and peroxide of iron. A portion of green vitri. i
however, remains mule composed, and tho quantity of this will be gree-
ns tho amount of the other salifiable buses contained in the schist K'co.^
reduced. When lime or magnesia is present iu the ore. they man'v.a-..
facilitate this decomposition, and afford corresponding amounts e:;he. ^-
sulphate of lime or sulphate of magnesia, which latter salt is ire'l^1'-^
ono of the secondary products obtained during tho manufacture of '^l11^.
alum from alum schist.. Tho undecomposed portion of sulphate oi no--._ •_
also wusheii mil. ;::ul crvstallised. and f.«-ms .in inmortunf item ni
also washed out and crystallised, ami forms tin important item i
proceeds of an alum manufactory^
When the shale docs not contain sufficient bituminous matter to «u
THE CRYSTAL PALACE AND ITS CONTENTS;
CRYSTALLISED SALTS. ~^^
_A_M01SrGST tlio various objects belonging to the Chemical Depart
none wcro ontitlod to a larger share of attention than the' v"'^'
Crystallised Salts, so valuable in their application to ni^nftust^118
processes. "-
First amongst these wa must mention the various largo and very beaut'r
specimens of the hydrated double sulphates of alumina and pptasli
ammonia, usually known by the name of common alum. This Bui'■■■■'-':
is sometimes discovevcel in a natural or native state ; ami wjiere ,
it occurs in volcanic districts in the form of a white flocculent powder
"™ermg the surface of lava and other trachytie bodies abounding ii Cr'
localities. In this form it occur
Sicily, and the vole
islands
l such
the south of France !,,
■them coasts ; but more piirtierda■)■'■
in the Grotto, di Ahnne on Capo Misenn
e lot ihtic it is colh ed I | ,
red-to deposit the earthy impurities ]lc]j
n'dcr to crystallise tlie alum which it con-
subsequently purified by repeated cm in).
revy minute
CAKBELMilUJJf.—BY MR. WEBB,
The candelabrum exhibited by Mr. Webb, of Bond-street, displayed great
merit, both in design and execution; stylo, that of the Venetian of the
sixteenth century. The cawing is bold" and effective, and the or-molu
branches are well arranged and beautifully chiscllod,
WAKDHOItl;.—by WII.KlXSOJf.
'fins wardrobe, in walnut-tree wood and pollard oak, is remarkable for its
good taste in the design, and simplicity in tho o mum en tat ion. It is not
ofteu wo meet with a work so uiieKueptiouaV.lv well linishej. with so little
attempt at meretricious display. (See p. 32S.)
tains. The salt thus procure
lisations. and, when brought into (he market, contains but a
amount of foreign matters. No fuel is used for the evaporation but the
natural volcanic boat of the soil in which the leaden pans are imbedded.
The alum thus obtained forms, however, but a very small proportion of
that which is annually employed in the arts; and much larger qiumti;:v;
are prepared in various localities by the chemical treatment of a niineiJ.
known by the name of alum-stono or alum-rock. This is a massive!
granular, partially crystallised, transparent, and not homogeneous rack'
which frequently enclose? quartz, sometimes iron pyrites and n 1 ancc:■;■*'■
ore. This mineral, which is a basic sulphate of alumina united with bu£
phatc of potash, is of a yellowish colour, sometime pas--:ug ;i:l> green or
brown, and is not unfrcquently found in the form of distinct crystals. Tho
ordinary alum-rock, although less pure than tho crystallised varieties, ha*
a nearly similar composition, and occurs in considerable - ::auvi-ie>. aiul m
a massive state, at Tolfa, near Civita Yccchia, in tho Papal States: a*
Montione, in the dukedom of Piombiuo ; in the Comitate of ISeregh ami
Zemplin, in Hungary; at Moht-d'Or, in France ; and in some of the islands
of tlie Greek Archipelago.
Alum is prepared from this substance by first burning the stones in
heaps or furnaces, and then transferring the residue to large wailed cistern-,
where it is repeatedly moistened will: water, and allowed to crumble j'w
three or four months; at the expiration of which Lime it is converted iiib
a, soft mud, tasting perceptibly of alum, which is subsequently washed out
with water and made to crystallise by the slow evaporation of the liquors.
Tho alum so obtained possesses most of the properties of ordinary seh:=:
alum, which will presently be described, but it has also certain distinct
characters, by which it may be distinguished from the latter salt.
The Roman alum always crystallises in opaque cubes, whereas tho
common variety assumes tho form of transparent octahedrons. It also
appears to contain a larger percentage of alumina than enters into die
composition of common alum ; for although perfectly soluble in pure water,
a deposit of that earth is determined by heating the solution to about
!U0 degrees Fahrenheit. The salt thus obtained is, however, of peculiar
value as a mordant for the purpose of lining colours, and as =ueh it is laiveiy
employed and much esteemed by the dyers of calico and other tc-xine tabfie-.
Originally the whole of tho alum consumed in Europe was produced nem
. alum-stone at Roeca, now called Edessa, in Syria—hence the name ''roc-
alum"-— and Was brought from the Levant to this and other European
: countries. About the year I-kiO the art of preparing alum was introduce:.!
! at Toll'a by Jolumn do Castro, who first discovered the alum-stone in ";■'■'
j district. Tho art spread from thence in various directions, and in m
| seventeenth century the manufacture of this substance was Qonunencw
both in this country and Germany, although tho materials used and tnc
I processes of preparing the salt wore very different from those previously
. employed for this purpose!
The greater portion of the alum at present consumed in the arts is aHHW
; from alum shale, which is a kind of clay slate impregnated with sulpinc'c-
I of iron and bituminous matters. This mineral is ton
! peninsula, in Bohemia, in the Harta, in Upper Bavaria, in Yoigtluud, ju L|:c
' mountainous districts of the Lower Rhine, near Whitby, in England, and °
I Hnrletand Campsie, near Glasgow. ...
When tiiese schists arc exposed to a high temperature, in contact »"a
air, the iron pyrites (or bi-sulphuret of iron) which they contain loses y:.»
one-half of its sulphur, and is converted into tlie simple sulphuret ot bi-
metal; which, speedily absorbing oxygon from the atmosphere, eecee;^
converted into sulphate of iron, or green vitriol. Th
transfers its acid to the clay with which it is mixed can ing hi 'tl
of sulphate of alumina and peroxide of iron. A portion of green vitri. i
however, remains mule composed, and tho quantity of this will be gree-
ns tho amount of the other salifiable buses contained in the schist K'co.^
reduced. When lime or magnesia is present iu the ore. they man'v.a-..
facilitate this decomposition, and afford corresponding amounts e:;he. ^-
sulphate of lime or sulphate of magnesia, which latter salt is ire'l^1'-^
ono of the secondary products obtained during tho manufacture of '^l11^.
alum from alum schist.. Tho undecomposed portion of sulphate oi no--._ •_
also wusheii mil. ;::ul crvstallised. and f.«-ms .in inmortunf item ni
also washed out and crystallised, ami forms tin important item i
proceeds of an alum manufactory^
When the shale docs not contain sufficient bituminous matter to «u