68 PROVOSTAYE ON THE ACTION OF 
nected with a tube A B more than a metre in length, contain- 
ing recently calcined ignited chloride of calcium. The other ex- 
tremity of this tube was bent twice at C and E, as represented 
in the figure. The first bend C was surrounded with a free- 
zing mixture; in this the sulphurous acid was condensed. The 
hyponitrous acid was introduced into the second bend EK. The 
tube was drawn out at its extremity, and terminated by a little 
funnel F. The hyponitric acid for the experiment was procured 
by distilling well-dried nitrate of lead, and was received ina 
U-shaped tube, surrounded by a freezing mixture. The appa- 
ratus being arranged, the retort M was detached, and the hy- 
ponitric acid poured in by the funnel F until the volume of the 
liquid in E nearly equalled that of the sulphurous acid condensed 
in C. The extremity B was then fused and sealed before the 
blowpipe; F was at the same time drawn out, and the two 
liquids mixed: the drawn-out point was immediately opened 
under an inverted jar of mercury. 
The two liquids have no sensible reaction, each resuming the 
gaseous state under the jar. Minute traces only of a white 
matter are observed attached to the sides of the tube. Thus it 
appears that these two bodies, when perfectly dry (at least under 
ordinary circumstances), do not combine in the liquid state. 
But if the tube be sealed at both the extremities, B and F, and 
the two liquids be afterwards mingled, the mixture is presently 
perceived to become green and turbid. By degrees a light-yel- 
lowish white deposit makes its appearance, which gradually in- 
creases for twenty-five or twenty-six hours, during which time the 
temperature of the tube is always above that of the surrounding 
bodies. The simple touch of the hand is sufficient to discover 
this. A small thermometer, not in contact with the tube, showed 
a difference of several degrees. About nine-tenths of the mass 
solidify. A green liquid remains above the deposit, the quantity 
of which is small when the hyponitric acid has not been employed 
in excess. On opening the tube, a sudden rush of gas occurs, 
which is sometimes very violent ; the green liquid disappearing 
and diffusing red vapours. It is advisable not to open the tube 
until the expiration of three days, and to have previously kept 
it for some time in a freezing mixture. In one of the first pre- 
parations of this substance, the tube, immediately on opening, 
was broken in a thousand pieces, and the fragments projected 
with so much force, as to pierce a large pane of a neighbouring 
