(412) 
The solution was not neutral however, although both ingredients 
were perfectly dry. Although they were dried for a whole week 
in a temperature of 45°, a moist red litmuspaper hung in the bottle 
above the liquid, turned blue after some time. Probably free am- 
monia clung to the dry powders. To get rid of it a solution was 
boiled in a glass receiver for some time, until a red litmuspaper 
did not turn blue in the vapour. This was the case after boiling 
from a quarter to half an hour. After cooling down, the liquid 
looked slightly unclear, which was easily amended by filtering. The 
loss of volume was restored with distilled water. 
The tincture was now ready; to keep it free of mould, it was 
needful to add an antiseptic; 1 pCt. chloral, recommended by 
Hoyer, proved efficient. 
This pikrocarmine !) is practically neutral, for a moist red litmus- 
paper hung in the closed bottle above the surface of the liquid, 
was not yet tinged blue after four months. 
The tincture*) contains }s pCt. ammoniumecarmine and 1 pCt. 
picrate of ammonium, for the loss of weight in consequence of the 
unclearness after boiling, is so insignificant, that it cannot be taken 
into consideration. The preparation is finished in two days; should 
time be short it could even be done in one day; in which case the 
drying is left undone, and after a preliminary experiment, the 
quantity can be ‘calculated which must be taken from the moist 
precipitate. The insignificant quantity of alcohol, which it contains, 
is of no consequence, and is moreover dispersed by boiling. 
A difficulty with this method is that an old carmine solution in 
ammonia must be used. Mine was two years old. Fresh solutions, 
and such as well which were half a year old, produced, instead of 
a black, a more or less clear red ammoniumearmine powder, which 
was only partly and uncleariy soluble in water. 
The carmine-solution must therefore “ripen”, how long, I have 
not been able to ascertain; but two years is not too much. The 
question now is wherein this ripening consists and if it cannot take 
place at once. It is well-known that a ripe solution (from which 
the superfluous ammonia has been allowed to evaporate as much as 
possible), stains the tissues better than a fresh one, and this is very 
generally — amongst others by GreRKE?) — ascribed to the for- 
1) To be obtained at the address of Dr. G. GrüBrer, Leipzig. 
2) One drop of the tincture on the filtering-paper gives, after being dried, a brown- 
yellow stain with red edge. This edge is much broader with the boiled, than with 
the unboiled liquid. 
*) H. Grerke, Färberei zu mikroskopischen Zwecken, 1885, p. 14 and 15, 
