164 THE NORTHERN MICROSCOPIST. 
PICRO-CARMINE SOLUTION. 
Take of Carmine*(fimest): )/ 7.32. .:.8.: soe eeee 2 grains. 
Liquid Ammonia (sp. gr. .960) ....... 4 drachm. 
Distilled Waterito > cere. +. 9.5. esneeee I OZ. 
Put the carmine in a two-ounce stoppered bottle, pour in the liquid 
ammonia, and shake occasionally until dissolved, then add the water; 
Miike OF BiCiic “ACG 5.05 someon ceies'ss= + + 2s sane aaa 8 grains. 
PIEOHOlS. op 5... soseeetemtes > 32 ase sce eeee eam I OZ. 
Dissolve in a test-tube with a gentle heat, then mix with the solu- 
tion of carmine. 
STAINING Process.—Place the sections in fifty per cent. alcohol 
for one hour, then treat with the recently filtered staining solution 
until the desired effect is produced (usually from half to two or 
three hours), remove the dye, wash quickly three or four times 
with alcohol 50°/,, then soak in an alcoholic solution of picrate of 
ammonia, changing this after the expiration of an hour, and allow- 
ing the sections to remain in the second solution for about the 
same period. 
Details of the process of mounting are given in the paper previ- 
ously alluded to (M. M. Journal, March, 1876). The logwood 
stained sections, after being well washed, are soaked in alcohol for 
an hour, then removed to oil of cajeput, and allowed to remain 
in this for a couple of hours ; at the end of this time transfer the 
sections to oil of turpentine. In less than an hour they will be 
ready for mounting in balsam or dammar. ‘The sections should 
not be allowed to remain long in the turpentine or else they be- 
come brittle. 
In the case of picro-carmine stained sections they should be 
removed ‘from the alcoholic solution of picrate of ammonia into 
alcohol for about a minute, then into oil of cajeput. 
The object of employing an alcoholic solution of picrate of 
ammonia is to avoid the loss of colour which attends the use of 
alcohol only, the yellow stain of picric acid being readily removed 
from the tissue by that liquid. Picrate of ammonia may be easily 
made by adding a slight excess of liquid ammonia to a solution 
of picric acid, and evaporating the mixture to dryness at a gentle 
heat. The residue is dissolved in alcohol and filtered. 
Wood sections stained in picro-carmine are very beautiful and 
permanent. The staining being done at ove operation, and the 
colours being remarkably selective, there is an absence of secondary 
tints, as in the case of most other double stains, especially where 
one tint is partially washed out to make way for another. 
Regarding permanence, I have some stained sections mounted 
nearly five years ago, which appear to me to have retained their 
brilliancy unimpaired. 
In place of alcohol, methylated spirit may be used if desired. 
