1324 
fuchsin-solution. It is only not so handsome in its application as 
oross-grained carbon, because it is inclined to pass through the 
filter, and easily too much of it is added to the fuchsin-solution. 
If one adds carefully so little carbon, that the decoloration takes 
place slowly, e.g. in the course of a day, then one obtains here 
also easily a light-pink filtrate, which after: some time becomes 
dark-red again. 
Now the question rises how the return of the color in the 
almost wholly decolored fuchsin-solution can be explained. It is 
not for me to answer this question. This will have to be done by 
chemico-physical methods by a person who is sufficiently conversant 
with the theory of carbon-absorption. As an histologist 1 can do no 
more than publish the fact I have discovered, hoping that somebody 
else will further investigate its nature. Yet I have tried to find 
for myself an explanation of the case, and have come to a working 
hypothesis, which after all proved to be untenable, but made me 
discover some other facts that may have importance for the expla- 
nation | tried to find. 
It was supposed, that in the almost decolored fuchsin-solution 
besides chlorine-ions or hydrochloric acid also uncolored dye kations 
or color-base would oceur and this even in so great a quantity, that 
they must partly reconstruct the dye, causing likewise the color 
partly to return. This cannot be a pure ion-reaction for ion-reactions 
have a quick process, and the color returns only slowly, but in the 
color-base an alteration of structure may have taken place, a 
phenomenon of which examples are known. 
Is it now possible to ascertain, that in an almost decolored 
fuchsin-solution more hydrochlorid acid and color-base occur than 
in an equally stained diluted fuchsin-solution which has never been 
in contact with carbon? Apparently it is. 
Silver-nitrate occasions in the almost decolored fuchsin-solution a 
distinct opacity, but does not do so in the as deeply stained diluted 
solution. Consequently there are in the former case more Cl-ions 
than in the latter. In fact this is in conformity with what FREUNDLICH 
and Loskv discovered. 
Adding a few drops of acetic acid causes the color to return 
quickly and intensely in the almost decolored fuchsin-solution, 
whereas an as deeply stained diluted solution does not change its 
color by it. So, perhaps the acetic acid enables the color-base in 
the decolored solution to form very quickly a colored salt, for which 
there is of course no opportunity in the diluted solution. 
| did not meet the phenomenon offered by fuchsin again in “Crystall- 
