ARTIFICIAL ULTRAMARINE. 
107 
given, is an improvement upon those first devised, and all 
that is now wanted is to discover the conditions for constant 
success. Here is a field for the " young chemistry*' of 
England, if it can be induced to withdraw itself for a short 
time from the discovery of organic bases. 
The essential constituent of ultramarine appears to be 
snlphuret of sodium ; yet on what does the splendid colour 
depend? — the arrangement of matter! As in the case of 
the brilliant scarlet biniodide of mercury, which is formed 
of a white liquid metal and an iron grey crystalline solid, it 
is impossible to explain the cause of the colours by reference 
to the existence of any colouring principle. For a long 
time ultramarine was'supposed, like the lapis lazuli, to owe 
its colour to the presence of iron. Clement and Desormes, 
however, prepared it without a trace of iron, and, what no 
one up to that time had suspected, they proved that it con- 
tained twenty-two per cent, of soda. 
Ultramarine, whether native or artificial, is a most dura- 
ble colour, and has great solidity ; it undergoes no change 
from the lapse of time, probably from its being already in 
the state of sulphuret. It is equally blue by daylight and 
in the yellow light of a candle, while inartificial light co- 
balt is violet, and other blues appear more or less green, 
unless admixed with lake or crimson to counteract the effect 
of the yellow rays. Ultramarine does not appear to have 
been known to the ancients, although the Egyptians, un- 
aided by chemical science, had discovered a most durable 
blue, now as bright on their mummy cases, as when first 
laid down three thousand years ago ! Upon the compost 
tion of this and the other colours used by the ancients we 
shall probably make some remarks on a future occasion. — 
Pharm. Journ. from Med. Gaz. 
