236 
COLORING MATTER OP DUTCH LITMUS. 
guished from the granular sugar from its being altered by 
acids, and from the liquid sugar in possessing a rotation to 
the right. Irs amount, which is pretty considerable in the 
liquid honey of the combs, diminishes in time, and may 
even disappear entirely in solidified honey. 
I have limited myself at present to the establishing the 
facts as they result from observation ; it is my intention to 
submit the honey of the combs to careful investigation, and 
also to inquire into the history of the curious transformation 
of the liquid into solid honey. Some experiments which 
are not yet completed, promise to throw considerable light 
upon these phenomena, and some facts of the same class 
which have already been published by M. Dubrunfaut. — 
Chem. Gaz.,from Coinptes Rendus. 
ART. LXXXL— ON THE COLORING MATTERS OF DUTCH OR 
CAKE LITMUS. 
By Jonathan Pereira, M. D., F. R. S. 
r The object of the present notice is to draw attention to 
the coloring matters employed by the Dutch to color cake 
litmus ; which, as is well known, is wholly imported from 
Holland. 
The essential coloring matter of this pigment is obtained 
from lichens. In England two dyes or pigments only, both 
of a purple color, are procured from these plants: they 
are orchil and cudbear; the former a liquid or pulp, the 
latter a powder. The substances which are essential to 
their production are certain lichens, water, ammonia, and 
oxygen (of the air.) By the united agency of the three 
latter substances on certain colorific principles contained in 
the lichens, one or more colored products are obtained, 
which, though probably not identical, pass under the 
