its properties are more delicate, I have repeatedly been able to detect
it satisfactorily, when I did not feel satisfied with the result of the
search for morphia. Dr. Ure made the same remark in his evidence on the
trial of Stewart and his wife. He detected the meconic acid, but could
not separate the morphia. It may be detected in one of two ways,—by
means of hydrosulphuric acid, or by sulphuric acid.
If the former method be chosen, suspend in a little water the
precipitate caused by the acetate of lead (par. 2); transmit
hydrosulphuric acid gas till the whole precipitate is blackened; filter
immediately without boiling; then boil, and if necessary filter a second
time. A great part of the impurities thrown down by the acetate of lead
will be separated with the sulphuret of lead; and the meconic acid is
dissolved. But it requires in general farther purification, which is
best attained by again throwing it down with acetate of lead, and
repeating the steps of the present paragraph. The fluid is now to be
concentrated by evaporation at a temperature not exceeding 180° F., and
subjected to the tests for meconic acid, more particularly to the action
of perchloride of iron, when the quantity is small. If there is
evidently a considerable quantity of acid, a portion should be
evaporated till it yields crystalline scales; and these are to be heated
in a tube to procure the arborescent crystalline sublimate formerly
described. About a sixth of a grain of meconic acid, however, is
required to try the latter test conveniently.
If the method of separating meconic acid by means of sulphuric acid be
preferred, the precipitate formed by acetate of lead is to be treated
with weak sulphuric acid, which forms insoluble sulphate of lead, and
disengages the meconic acid. The liquid obtained by filtration is then
to be evaporated as above, to obtain crystals, which are to be examined
by the tests for meconic acid. Orfila thinks this method more delicate
than the mode by hydrosulphuric acid gas. I am inclined from my own
experiments to doubt his statement.