DR. KANE ON THE CHEMICAL HISTORY OF ARCHIL AND LITMUS. 
301 
or 73. The total quantity of these substances is, however, very small, and it is neces- 
sary to operate upon at least a pound of commercial litmus to obtain twelve or 
fifteen grains of erythrolein. 
Regarding the origin of this substance, 1 shall make no remark until the substance 
next in order has been described. 
II. Of Erythrolitmine. 
This substance, which from its composition and the quantity in which it exists, 
constitutes one of the most important ingredients in litmus, is to be obtained in the 
manner described under the head of the general analysis of litmus. By exposure to 
a temperature of 230° Fahr. for an hour or two, it may be completely freed from all 
chance of contamination by adhering ether. 
It is of a beautiful and pure bright red colour, without any tinge of crimson. It is 
sparingly soluble in water, which it colours red : very sparingly soluble also in ether, 
which it scarcely tinges, but abundantly soluble in alcohol, forming a fine deep red 
liquor, which if saturated when boiling, deposits on cooling a considerable quantity 
of erythrolitmine under the form of small soft granular crystals, which are not at all 
brilliant, though of a fine deep red colour. This is the only colouring substance in all 
this series, in which I have been able to detect the slightest disposition to crystallize. 
In a pretty strong solution of potash the erythrolitmine dissolves, giving a blue 
liquor. With ammonia it combines, forming a blue substance, which has the singular 
character of being totally insoluble in water. Although the erythrolitmine is itself 
very sparingly soluble in water, yet if water tinged by means of it be mixed with 
some water of ammonia, the blue compound gradually subsides, or may be removed 
by filtration, leaving the liquor absolutely colourless. The separation of this erythro- 
litmine-ammonia may be accelerated by boiling. This blue compound is, however, 
very instable ; it cannot be dried without losing ammonia and becoming reddish 
purple. In this state it still retains a portion of the ammonia very firmly, so that it 
cannot be separated by means of heat. The erythrolitmine combines with metallic 
oxides, and forms lakes of a very fine purple colour ; their preparation, however, re- 
quires precautions, to which I shall hereafter direct attention. 
The erythrolitmine dried at 212°, gave on analysis the following results, with sepa- 
rate specimens. 
A. 0-422 gramme of material gave 0-853 of carbonic acid, and 0330 of water. 
B. 0-423 gramme of material dried at 250°, gave 0-844 of carbonic acid, and 0-31 1 
of water. The composition indicated by these results is 
Theory. 
26 Carbon = 158'6 55*53 
A. 
55-78 
B. 
‘ 55-3 
23 Hydrogen = 23 0 
8-05 
8-69 
8-1 
13 Oxygen = 104-0 
36-42 
35-43 
36-6 
285-6 
100-00 
100-00 
ioo-o 
