by chloride of sodium, chloride of calcium, and carbonate 
of soda. It occurs very pure in the lower lias at 
Miihlecken in Aargau. In the air it falls to a white 
powder, from losing its water of crystallization. It is 
easily soluble in water, the solution has a disagreeable 
bitter-saline taste, and gives no precipitate with carbonate 
of potash, as is the case with Epsom salts, with which it 
sometimes occurs. Before the blow-pipe it melts easily, 
and colours the flame yellow; sulphuret of sodium is formed 
in the inner flame on charcoal. Its occurrence is very 
limited; in general it is found along with rock-salt, as, 
for example, in the Salzburg district, with Epsom salts at 
Saidschiitz in Bohemia, and at Carlsbad. 
Beussin is a mixture of glauber salts and sulphate of 
magnesia, and occurs at Sedlitz in Bohemia. 
Bloedite consists of equal parts of sulphate of soda and 
sulphate of magnesia, with five equivalents of water, and 
is found at Ischl. 
Glauberite , also klinorhombic, consists of equal quanti¬ 
ties of sulphate of lime and sulphate of soda; it occurs in 
a crystalline state at Berchtesgaden, and Aussee in Aus¬ 
tria, and in Spain. 
Thenardite is anhydrous sulphate of soda; it crystallises 
in right rhombic prisms, gives off its water in the atmo¬ 
sphere, and then falls down to a powder. It is found at 
Salines d’Espartines, near Madrid. 
Glauber salt is principally used in medicine. It is 
seldom prepared from the natural salts just mentioned, 
however, but is for the most part obtained as a secondary 
product; as, for example, from the remains of the manu¬ 
facture of nitric acid, from Chilian saltpetre, or also from 
the bittern of many salt springs, in which it seems to be 
present from the decomposition of chloride of sodium by 
sulphate of lime. 
Fig. 22.—Boeax, Boeate of Soda, Tincal. 
This salt crystallises in oblique rhombic prisms of 
86° 30' and 93° 30', with cleavage in the direction of the 
planes of truncation of all the lateral edges, so that an 
oblique rectangular prism readily arises. It occurs some¬ 
times in its primary form, sometimes with truncation of 
the acute basal and lateral edges (Fig. 22), also as twins; 
forms which often present much similarity to those of 
common augite. Colourless, passing into grey and yel¬ 
lowish, but little lustrous, translucent, of 2*0—2-5 hard¬ 
ness, and 1*5—1*7 specific gravity. Beadily soluble in 
water, and fine crystals may be obtained from the solution, 
which has a sweetish, somewhat alkaline taste. The 
elements are a bi-borate of soda, with 10 eq. of water 
= Na B 2 + 10 H. It melts before the blow-pipe with 
great intumescence to a colourless glass, in which all metallic 
oxides and silicates are readily fused; and on this account 
borax is generally used in blow-pipe experiments. Borax 
is also used in solder, having the property of keeping the 
pieces of solder free from oxidisation, and of favouring the 
purification of smooth metallic surfaces. It is otherwise 
used as an ingredient in the manufacture of enamel and 
coloured glasses, the fusion of which it furthers. Purified 
borax is, however, generally used for this purpose. Of 
late years, much borax has been prepared from the natural 
boracic acid or sassoline , which occurs, collected in the salt- 
springs and small pools, at Sasso in Tuscany, and also in 
the Lipari Islands. It is hydrous boracic acid = B + 3H. 
Sometimes rendered impure by sulphur gypsum and sul¬ 
phate of manganese, and forms oblique rhomboidal laminae, 
acicular crystals and scales, which feel unctuous to the 
touch, and have a cooling, acid taste. They are thus 
soluble in water and spirits of wine. 
Borax is found on the shores of a salt lake in Thibet, 
in Persia and South America; the rough borax is also 
sometimes brought into commerce in crystalline masses 
and crusts. There are also combinations of borate of lime 
and borate of soda in different proportions, which are 
known as borocalcite and boronatro-calcite. Found with 
nitrate of soda at Iquique in Chili. 
XI. SALTS OF MAGNESIA. 
Figs. 18 and 19.— Boeacjite. 
Boracite is borate of magnesia = Mg 3 B 4 , and crystal¬ 
lises in tetrahedrons like grey copper or fahlore (Plate XY. 
Figs. 18, 19, 20). It occurs more frequently in combina¬ 
tion with the cube and rhombic dodecahedron (Fig. 18), 
so that the planes of the cube predominate, or else the 
tetrahedron is truncated at the edges (cube), and bevelled 
at the angles with three planes (pyramidal tetrahedron, 
Fig. 19). The small crystals have a vitreous to an ada¬ 
mantine lustre, the larger ones are usually dull, the colour 
is white, passing into grey and greenish; the small crystals 
only are transparent. The hardness is very considerable 
= 7*0, the specific gravity 3. Insoluble in water. Before 
the blow-pipe it melts with evolution of air-bubbles to a 
crystalline-radiated pearl, and colours the flame green. It 
is found imbedded in the gypsum at Segeberg in Holstein, 
and in the limestone mountains at Luneburg, 
Fig. 24.— Epsomite, Sulphate of Magnesia, 
Epsom Salts. 
The primary form is a right-rhombic prism, which 
occurs with truncation of the acute lateral edges, and of 
all the basal edges; sometimes with further truncation of 
the two vertical edges (Fig. 24), and more frequently still 
with hemihedral bevelling of the terminal planes, or in 
spear-like needles and long fibres. Colourless, lustre vi¬ 
treous to adamantine, translucent to transparent; hardness 
2*0, specific gravity 1*75. The elements are simple sul¬ 
phate of magnesia, with 7 eq. water = Mg S + 7 H, 
composed of 18 of magnesia, 33 of sulphuric acid, and 48 
of water. It does not effloresce in the atmosphere, and 
maintains its lustre; it is readily soluble in an equal volume 
of water. The solution has a bitter saline taste, and gives, 
with carbonate of potash, a white precipitate of carbonate 
of magnesia, which is soluble with effervescence in nitric 
