14G 
The purple coloring matter differs entirely from the 
colorless principle from which it is obtained, not only by its 
color, but also by other physico-chemical properties; thus, 
for instance, it is less soluble in water and in ether, more 
volatile, and contains a greater proportion of carbon, than 
the colorless principle. It may be reduced in the same 
manner as indigo blue. 
Amongst the many interesting experiments which may be 
performed with this coloring matter, and of which several 
were repeated during the evening, we may mention the 
following. A quantity of the colorless solution is introduced 
into a glass tube, from which the air is then expelled, and 
the tube hermetically closed. If the tube be now exposed 
to the direct rays of the sun, the solution assumes a purple 
color, and red flakes of coloring matter are deposited. When 
acidulated with hydrochloric acid, the colorless solution 
acquires a purple hue when heated up to 80° C. If the 
colorless principle in the dry state be enclosed in a tube 
containing hydrogen, or devoid of air, and exposed to a 
temperature of 160° C., in the dark, the purple colour is at 
once produced. 
The wood and its decoction show the same phenomena, 
but with less intensity. Woollen, silk, and cotton stuffs, 
with or without mordant, steeped in this decoction have only 
a brown or greyish hue, as long as the original substance has 
not been modified. But w'hen so prepared they are exposed 
to the action of light or heat, or immersed in a bath of acidu- 
lated water, they are at once dyed of a purple hue. 
The colour thus produced withstands perfectly the action 
of acids, it is rendered slightly more blue by alkalis, and 
resists light better than archil purples and aniline. 
A second research is on the Bois de Taigu, from Paraguay 
(or Ebene soufre), from which the Author has separated an 
acid principle, which crystallizes in beautiful yellow prisms, 
and yields crystallizable salts of a scarlet colour. 
