64 
SELECTED ARTICLES. 
and ammoniacal salts; if, on the contrary, it be pushed too 
far, the density and viscidity of the mass prevents crystalli- 
sation, and meconine and narceine will not be obtained. To 
this cause I attribute the want of success of some chemists who 
have repeated my experiments. The great point is to reduce 
the mother waters to a crystallisable point. This can be done 
by acidulating them with hydrochloric acid, then evaporating 
to the consistence of a thin syrup; this, when kept in a cool 
place, will become of a honey-like consistence, from the oc- 
currence of thousands of crystals, so small that they are often- 
times only to be distinguished by their sparkling when ex- 
posed to the direct rays of the sun. This mass is to be poured 
on a linen filter, and the thick and viscous fluid that escapes 
is to be kept for further examination. 
To purify the crystals, after having subjected them to pres- 
sure in a cloth, they are to be dissolved in alcohol, 36° B., 
with the aid of a gentle heat. In this operation considerable 
quantities of caoutchouc and extractive matter are separated. 
The alcohol must be saturated as far as possible, so as to ob- 
tain a crystalline mass on its cooling, or, at all events, aftei* a 
slight evaporation; this crystalline matter is to be redissolved 
in a small quantity of boiling water, treated with animal char- 
coal, and again crystallised. 
The alcoholic mother waters will afford a further supply of 
crystals, by spontaneous evaporation; these are to be treated 
in the same manner. The crystals must, in fact, be rendered 
as white as possible by repeated solutions and recrystallisa- 
tions, taking care at the same time that the mother waters are 
exhausted at each repetition of the process. I would here re- 
mark that the successive employment of alcohol and water 
is requisite, because the purification of the crystals depends on 
two circumstances, — crystallisation and decolouration by ani- 
mal charcoal; and it is well known that the latter is better 
accomplished by the aid of water, whilst the former is more 
perfect through the medium of alcohol. The crystals thus 
purified, were subjected to a series of experiments, which need 
not be enumerated, but which were intended to determine 
