APPARATUS FOR PREPARING NITROUS OXIDE GAS. 
65 
upon a column of water supports the same at various heights in proportion to 
its force; and the idea is brought into action by having a float in this column 
attached’to a lever which has for its fulcrum the plug of the gas-tap that sup¬ 
plies the heat. 
Its working is as follows :—When the gas generated in the flask by the heat 
of the burner (X) increases so as to produce a pressure within (C), beyond 
that escaping by the wash-bottles, and, therefore, upon the surface of the fluid 
in (D), it causes the latter to rise in the tube (F), and, in proportion to the 
pressure, so will be the height thereof, and also of the float (_/"). Now, as. the 
float is attached to the end of the lever (G), and is counterpoised by the weight 
(I); and since the lever is essentially the gas-tap, it follows that the rising and 
falling of the column in (F) will, by its connection, raise or lower the arm (G, H), 
or, in other w r ords, turn off or on the supply of heat; so that if the gas is 
liberated too quickly because of the excess of heat, it exerts a pressure, raising 
the column and turning off the heat, when the evolution of the gas and pressure 
will diminish, and the heat be turned on again. And thus it moves up and 
down until it attains a position where the pressure and heat are balanced, and 
there it will remain four or six hours, or as long as the nitrate of ammonia lasts. 
The arm of the lever is prevented from quite extinguishing the gas by a stop, 
so that when the pressure diminishes, the gas may re-kindle, which is a great 
advantage. If by any means the exit of the gas is closed (as by the doubling of 
the india-rubber tube, the bag being full), or should the gas be generated too 
fast, from the lamp being too close, or any such cause that would increase the 
pressure, then the column of water would gradually rise, at first turning the 
tap off to its stop, and then force so much water into the pressure-tube as to 
diminish the height of the water in the bottle below the orifice of the tube (E), 
when the gas rushes up, sounding the whistle on the top, to give an alarm that 
something is amiss. 
Then, taking a general view, we have an apparatus that will, when the gas 
is going too slow, turn on its own heat, or, when going too fast, turn it off, and, 
should the pressure become dangerous, will indicate the same by sounding a 
whistle. When the nitrate is exhausted, and the heat turned ofi', the vacuum 
caused in the flask is supplied by air being drawn in through the whistle, pass¬ 
ing into (G) and up the tube (B) into the flask (A), so preventing any accident, 
which often happens when the tube from the retort is under water. 
This apparatus, although it may be considered as an addition to the ordinary 
arrangement, does indeed perform the most important function of them all, 
inasmuch as it prevents so many disastrous effects that result from the supply 
of heat not being properly regulated, such as the production of higher com¬ 
pounds of nitrogen, as nitric oxide, nitrous anhydride, and even nitric peroxide, 
together with free nitrogen from excess of heat, as well as the bubbling over 
of° the fused nitrate, that sometimes solidifies in the tube of _ the flask, 
causing the latter to burst, which is often attended with serious injury to the 
operator, as it may contain three or four pounds of fused nitrate of ammonia at 
a temperature near to 400° Fahr. It also has great advantages over others, in 
that there is no need for disconnecting the tube of the flask, because any 
vacuum formed in the' latter is supplied with air drawn through the whistle 
into the bottle (C) and flask ; it also saves the trouble in moving the gas 
and watching the whole time it is being made, as well as ensures the purity 
of the gas ( i. e. if the nitrate of ammonia be pure). With an apparatus of this 
kind and four pounds of nitrate of ammonia, 100 gallons of gas have been pro¬ 
duced in four hours, without any more attention than that of starting the 
operation. 
VOL. XI. 
F 
