COLORING MATTER OF DUTCH LITMUS. 
337 
general name of orceine. In order to obtain the well 
known blue color which is essential to the production of 
cake litmus, it is necessary to use, in addition to the ingre- 
dients above mentioned, a fixed alkali, namely, either pot- 
ash or soda. Without this the product would be purple, 
in other words, it would be orchil or cudbear. The Dutch 
manufacturers use,' I suspect, potash ; for if a cake of litmus 
be ignited in the outer cone of the flame of a candle, the 
flame acquires a whitish violet tint, indicative of the pre- 
sence of this alkali. This suspicion is confirmed by the 
statement of Ferber, who saw litmus in process of manufac- 
ture at Amsterdam, and who tells us that besides the lichen, 
there were employed urine, lime-water, slacked lime and 
potashes. The urine was used to yield, by decomposition, 
carbonate of ammonia; and the carbonate of potash, and 
probably was otherwise useful in the process. 
In order to give body to the blue coloring matter thus 
produced, and which I shall provisionally call lichen blue, 
the Dutch employ some one or more earthy substances, to 
enable them to form the litmus into cakes. Ferber does 
not appear to have been aware of this ; for he says that the 
lichen has been sufficiently macerated, and the blue color 
developed, the mixture is ground iu a mill, which, he adds, 
he was not allowed to inspect. I presume that the Dutch 
manufacturer used something, in this part of the process, 
which he was anxious to keep secret. 
The presence of the mineral or earthy constituent of lit- 
mus is readily shown by exposing some cakes of litmus, in 
a platinum or glass capsule, to the heaX of a spirit lamp. 
The coloring matter is volatilized and destroyed, leaving 
the fixed constituents, presenting the volume and shape of 
the original cakes. Into the composition of the ashes of 
litmus it is not the object of this paper to enter. 
In order to give these cakes a strong blue color, the Dutch 
manufacturer introduces into the paste another blue color- 
ing matter, namely, indigo. Hitherto no one has alluded 
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