beautiful
collection of cups, knife-handles, and ornaments in this stone. There
is a great profusion of it in the palace which Catherine Π. built at
St. Petersburg for Orloff ; it richly adorns the villa palace of the
Demidoffs at Florence, and the altars of St. Paul outside the walls of
Rome. In China, statuettes and idols are made of it.
The
colour which painters call ultramarine is made of lapis lazuli. We have
the testimony of Camillo Leonardo that the production of ultramarine
was known in Italy, most certainly from the year 1502, under the name
of azurum ultra-marinurn.
The Chinese have used it for a long time in painting on porcelain, and call the beautiful lapis lazuli zui sang ; and that which is darker, and marked with pyrites of iron, tchingtchang. They choose the latter for making idols, cups and snuff-boxes.
True
ultramarine is prepared chiefly in Rome. Its specific gravity is 2·36.
It costs from 200 to 300 lire the ounce; and to this high price must be
attributed the efforts made by painters and chemists to substitute
other substances for it.
In
1828 Professor Gmelin discovered that sulphate of soda would do as a
substitute. By dint of study, he succeeded in extracting that substance
from silex, alumina, i-oda and sulphur; and now his production sells at
the low price of 80 lire the kilogramme.
