PNEUMATIC COMPRESSION SQLTRTERS. 
255 
corked bottle, or other vessel, contained in a larger tight jar or vessel 
with the bicarbonate between the two, so that by tipping the whole more 
or less of the acid is turned into the carbonate. 
Plate XXXV, Fig. 3, shows a plan for generators of this kind, in 
which the acid bottle, fl, in the interior is surrounded by the bicarbonate, 
b, in an ordinary two-quart fruit jar with a lead screw-cap perforated 
by the outlet spout, c, for exit of the gas which is conducted through 
the hose, fc, into the top of the b.irrel or reservoir containing the poison. 
By having the two chambers thus compactly conjoined the apparatus 
is simple and handy as a small generator. 
But there are certain advantages in having the two chambers separate 
and connected by means of a flexible tube, and this construction is surely 
one often to be preferred for large generators, when a cheap home-made 
apparatus is wished. The short piece of flexible tubing should be of 
good rubber, and although the acid corrodes it somewhat, it will endure 
for one season at least, when B new piece can be substituted at a trilling 
cost. Fig. 1 in plate WW shows this apparatus. The jar, f, contains 
the bicarbonate, b. Its screw-cap, f, is made of lead. From this is a 
lead outlet tube, r, coupled to the reservoir, r, of poison, p. The cap is 
also perforated by the lead tube. /', coupled to the hose, A, leading from 
the acid-bottle, a. The latter is to be elevated and inclined by one hand 
to pour the acid into the bicarbonate. Thus at intervals a few minutes 
apart a little acid is added. When the driver sees that the spra\ is not 
going as high as desired he applies a little splash more of the acid to 
increase the pressure. This is one of the easiest ways in the world for 
spraying poison. I: is really more pleasure than labor. In the gen- 
erator, t b, considerable heat is evolved and it will often become too Wot 
to be handled. On this account it had better lie so fixed that it need 
not be touched and its temperature may be kepi down by keeping it 
wet. It is easily hauled or carried in a bucket containing some water 
with a little soft packing material beneath and around it. The less the 
amount of water mixed with the bicarbonate, the less heat will be gen- 
erated, but enough water should be employed to wet the soda, other- 
wise the sodic sulphate formed by the chemical process arises as a crust 
aud keeps the acid from reaching the remainder of the bicarbonate, 
thus retarding or stopping the generation of gas. 
These pressure generators are cheap, of simple construction, easily 
Understood and used by any one, while the action is under perfect con- 
trol, and danger from bursting does not exist. There is no need of 
putting in too much acid and running the pressure too high. 
The rubber gum hose is stout enough to squirt the poison as high as 
needed, but the gum will give way and burst before a pressure if any 
danger is attained. Thus there is nothing to fear from explosions. 
The acid is a very injurious poison and should be handled with great 
discretion; but the bicarbonate used with it is always at hand as a sure 
antidote, and on the ground of its being dangerous the acid is no more 
