A novel device is described for the quantitative application of chemical st
imuli. The device uses ultrasound to disperse a solution of volatile chemic
als as an aerosol. A motor-driven syringe controls the rate at which the so
lution is released from a glass capillary. Vibration of the capillary dispe
rses the released solution into microdroplets that evaporate completely wit
hin a few centimeters of the tip. The ratio of chemical stimulus to solvent
is maintained until the liquid is dispersed and therefore the release rate
of the chemical stimulus can be set and calculated straight-forwardly from
the dilution factor and the dynamically controllable speed of the syringe
plunger. The sprayer permits the delivery of chemical stimulus independent
of relative vapor pressures of the components and of environmental factors
such as temperature. The sprayer is easy to operate, can be constructed fro
m inexpensive materials, and can be used to emit odor stimuli in the wind t
unnel or any other bioassay for pheromones and plant volatiles.