(1.) To the weight in grams found add ·20 for loss of oleic acid in
solvent, and then say as 95 : 100 :: total oleic acid.
(2.) Calculate the per-centage from the quantity taken, and from this
deduct 6 per cent. for possible altered resin in the balsam. The error,
owing to the correction, of course, increases with the amount of oil
present; but it is stated to be always an error in the direction of
under-estimation, which is the great point for public analysts. When
working on 3 to 4 grains with an admixture of not over 25 per cent. the
errors due to loss of oleic acid and insoluble resin soap are said to so
nearly balance each other, that any correction is unnecessary, and the
actual amount of oleic acid found may be taken as correct within a per
cent.
9. (B. P.) According to the British Pharmacop[oe]ia, copaiba should be
soluble in an equal bulk of benzol.
10. (The evaporation test.) Mr Siebold says: "This is an excellent and
exceedingly simple test, but is clumsily applied by many. Instead of
boiling the balsam with water for many hours, a small quantity (about 1 to
1·5 gram) of the sample should be carefully heated in a watch-glass until
all the oil is driven off, which is the case as soon as the residue has
assumed a rich brown colour. A few minutes suffice for the experiment.
"If the remaining resin is perfectly brittle and pulverisable there is no
fatty matter present, for 1 per cent. of oil would diminish the
brittleness of the resin, so that it cannot be reduced to a fine powder.
One per cent. of oil is thus readily detected, and with larger quantities
of the adulterant (3 to 5 per cent.) the resin feels quite sticky.
"On heating the resin castor oil and linseed oil may be distinguished by
the odour. By mixing the adulterated balsam with ten, twenty, forty, and
fifty volumes of pure maranham balsam respectively, and testing each
dilution in this manner, it is easy to find in which the oil has been
reduced to below 1 per cent., and thus to ascertain whether the adulterant
amounted to more than 10, 20, 30, 40, or 50 per cent., and this, I think,
would be sufficiently near the mark for the purpose of public analysts."
_Uses, &c._ Balsam of copaiba is considered detersive vulnerary, diuretic,
and astringent; and appears to possess a sort of specific power over
diseases of the mucous membranes of the urino-genital organs. It is hence
a favourite remedy in gonorrh[oe]a, as soon as the first inflammatory
symptoms have subsided, antiphlogistic and soothing measures being
previously adopted. _Dose_, 20 to 60 drops on sugar, floating on water, or
made into an emulsion with yolk of egg or gum arabic, 3 or 4 times daily,
if the stomach will bear it. The addition of a few drops of sweet spirits
of nitre and laudanum have been recommended, to allay the nausea. By
adding 1 dr. of oil of orange (ol. aurantii) to each oz. of the balsam,
its flavour becomes far from disagreeable, and it sits well upon the
stomach. Copaiba is also given in capsules and pills. See CAPSULES,
EMULSION, OIL, PILLS, &c.
_Obs._ Numerous preparations of this article are sold under such names as
'soluble copaiba,' 'specific solution,' 'salt of copaiba,' &c.; none of
these appear to possess equal activity and certainty of operation to the
natural balsam. As the whole virtue of copaiba as a medicine depends on
the essential oil it contains, the value of any of these preparations may
be estimated by the quantity of that article which is found in them. In
the case of the first two articles above named the quantity is very small
indeed, and in the last it is wholly deficient.
The following forms are current in the trade for the reduction
(adulteration) of balsam of capivi:--