( 411 ) 
partly be considered as a modification and simplification of Hoyer’s 
prescription '!) running thus: 
Take 25 ec. *) of an old strong *) solution of carmine in ammonia 
and pour it carefully in 100 cc. of strong alcohol (of circa 96 pCt.), 
a voluminous precipitate of ammeniumearmine now forms itself. 
Filter after half an hour or longer, rinse the precipitate on the filtrum 
with 100 cc. strong alcoho] and dry it for 24 hours in a thermo- 
state of 40—45° C. ©. 
If the solution was old enough a dark red, nearly black crumbled 
mass is obtained, which is easily rubbed down to a powder tho- 
roughly and clearly soluble in distilled water or in picrate of ammonium 
of whatever strength. If picrie acid is added to the solution, a 
precipitate is immediately formed; the picrate of ammonium may 
therefore not contain free picric-acid which was the case with a 
certain quantity which I received from Mercx °). 
The relative proportion of ammoniumcarmine and picrate of am- 
monium, which, as a rule, seemed to me most favourable for staining 
was as 1: 2. In order to obtain a liquid, which would at the 
same time fix the tissues to some extent (as pikrocarmine is ex- 
pected to bring about), I took a 1 pCt. solution of picrate of am- 
monium, — i.e. a nearly concentrated solution ®) and added thereto 
1, pCt. ammoniumearmine. 
1) Hover, Beiträge zur histologischen Technik, Biologisches Centralblatt, Bd. 2, 
1882. Following the somewhat lengthy prescription of Horver, I was not successful 
in obtaining a powder quite soluble in water. Besides a good deal of carmine is lost. 
The “Pikroearmin nach Hoyer” of GRÜBLER must, according to the List of Prices, 
be dissolved with ammonia, and could therefore not be used for my purpose. 
2) These and other quantities are of course taken ad libitum, the statement is for 
the convenience of those who may want to follow the prescription. 
*) At first I dissolved 30 gr. carmine in 100 cc. not diluted ammonia of circa 
10 pCt. Afterwards I found out that the carmine dissolves better in ammonia diluted 
with the double quantity of distilled water. 
1) The filtered liquid is thrown away. After evaporation a tough red substance is 
obtained, which, when thoroughly dried forms a ccherent, hard mass, soluble in 
alcohol as well as in water. With alcohol the watery solution gives no precipitate. 
In the same manner it appears that the solution of carminic acid in ammonia con- 
sists of two kinds of ammoniumearmine, one of which can be precipitated by strong 
alcohol, but the other cannot. 
5) A sample, which I received from GRrÜBLER was excellent on the contrary. 
Picrate of ammonium can easily be prepared. For instance 9 gr. picric-acid are 
dissolved in 100 ee. alcohol of circa 96 pCt. adding 15 cc. ammonia and evapo- 
rating on the thermostate at about 60°. 
*) In winter crystals are formed in the 1 pCt. solution of picrate of ammonium. 
To prevent the stain from crystallising in winter, it can be diluted with half the 
quantity ‘of distilled water. 
30* 
