An apparatus is assembled in the hood, as shown in
f.htmig. 1. In the
2-l. globe-shaped separatory funnel H (stopcock J closed) is placed 1.3 l. of deaerated water (Note
1).
Three-holed rubber stopper G (bearing the stem of a 125-ml. separatory funnel C with stopcock D closed, a long inlet tube E, and a short outlet tube F) is inserted in the neck of H. In the neck of
C, a rubber stopper
B, provided with an inlet tube
A, is inserted.
H is flushed with
nitrogen (Note
2) admitted at
E. To the water is added
16.0 g. (0.1 mole) of alloxan monohydrate (Note
3), and the mixture is stirred by the flow of
nitrogen through
E until the
alloxan monohydrate has dissolved. The
nitrogen flow is discontinued, and
hydrogen sulfide (Note
4) is passed in at
E until the mixture is saturated with this gas and the aqueous solution is free from opalescence (about 2 hours).
Carbon disulfide (100 ml.) is now added, and the mixture is agitated for 5 minutes by means of the
hydrogen sulfide gas stream. The
carbon disulfide layer is then cautiously withdrawn through
J and discarded, and the aqueous solution is washed once more with
100 ml. of carbon disulfide which is separated and discarded. The
hydrogen sulfide flow is discontinued, and
nitrogen is passed in at
E for about 2 hours or until the gas emerging at
F gives no more than a faint test for
hydrogen sulfide with lead acetate paper.
Tubes
E and
F are now closed, stopper
B is loosened, and
C is flushed out with
nitrogen admitted through tube
A. Deaerated water (100 ml.) is placed in
C, which is then flushed with
nitrogen. To this water is added
alloxan monohydrate (16.0 g.; 0.1 mole), and the mixture is stirred with
A, while the
nitrogen stream is continued, until the solid has dissolved.
B is now pushed down to give a tight fit, a slight pressure of
nitrogen is applied (at
A),
F and
D are opened, and the solution is allowed to pass from
C into
H. To wash out traces of
alloxan, a further 10 ml. of water is placed in
C and run into
H.
D is closed, and
nitrogen is passed in at
E and out of
F until the solutions are thoroughly mixed.
E and
F are now closed, and the mixture in
H is allowed to stand until crystallization is complete (overnight). In the meantime, the stem of funnel
H is inserted in one hole of the two-holed rubber stopper
L (also bearing inlet tube
K);
L is inserted in the mouth of
M (a
150-ml., Pyrex Büchner funnel with coarse, fritted-glass septum); and the stem of
M is inserted in the rubber stopper
N placed in the neck of a
2-liter Büchner flask P (side arm,
Q). To flush out
M and
P,
nitrogen is passed in at
K and out of
Q.
K and
Q are now closed,
F is opened, and a slight pressure of
nitrogen is applied at
F.
Q and
J are opened, and, if necessary, slight suction is applied at
Q. When all the suspension has passed out of
H, the
nitrogen stream is continued for a few minutes, to remove as much as possible of the liquid clinging to the precipitate in
M. Then
F, J, and
Q are closed. The Büchner funnel
M and its contents are quickly removed, placed in a
vacuum desiccator (preflushed with
nitrogen), and dried to constant weight, at room temperature, over
phosphorus pentoxide and soda-lime. The yield is
27–27.5 g. (
84–85%) (Note
5), (Note
6), and (Note
7).