THE MICROTOMIST 'S VADE-MECUM

solution that is necessary for neutralisation of a given quantity
of the ammonia employed, is not infallible because it often
happens that commercial gelatin is acid; in which case, the
proposed method would cause the operator to overpass the
point of saturation.
The mass having been perfectly neutralised is strained
through new flannel.
391. Gelatin Injection-mass (Carmine) (Gerlach's formula 1):
Carmine     .    .     .    .    .    .     5 parts
Water          .       .    .    .     .    4
Ammonia     .    .     .    .    .    .    0-50,,
Dissolve, and combine with following vehicle whilst warm:
Gelatin   .    .    .     .    .    .     .    6 parts
Water     .    .     .    .    .    .     .    8
Add to the mass a few drops of acetic acid.
Ranvier does not recommend this mass.
392. Gelatin Injection-mass (Carmine) (Thiersch's formula2):
Take of-
Carmine .         .       .    1 part by weight
Liq. Am. .     .     .    .    1
Water       .       .     .    3
Dissolve and filter.
Then take a solution of 1 part by weight of gelatin in 2 of
water. Warm it to 250 R. in a water-bath, and mix 1 part of
the carmine solution to 3 or 4 parts of the gelatin solution.
Then add acetic acid, drop by drop, stirring continually, until
no more ammonia remains free, as tested by the smell, by the
non-formation of vapour when a glass rod moistened with
acetic acid is held over the solution, and by moistened cur-
cuma-paper held over it. (The carmine solution may be
neutralised before mixing with the gelatin, if desired. The
excess of ammonia may also be got rid of by evaporation at
from 250 to 300 R.) Inject at a temperature of from 250
1 Ranvier, ' Traitg,' p. 118.
2 'Arch. Mik. Anat.,' i (1865), p. 148.

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