178 
GOETZ AND PREINING 
Fre. 10—Scheme of generator for artificial aerosols 
ficial aerosol production under carefully con- 
trolled conditions of dynamic stability. The as- 
sembly and procedure developed for this purpose 
is described in the following. 
Generation of aerosols—The aerosol is generated 
from suspension or solution by the calibrated 
nebulizer N, supplied by branch I of a compressed 
air system, (Fig. 10). The air passes a dense 
cotton filter F; and subsequently either the tube 
G; or the bypass S$: , depending upon the posi- 
tion of the valve pair Vy. G; is lined with coiled 
filter paper impregnated with organic liquids of 
low volatility; it acts thus as source for gaseous 
traces to the air flow. N is submerged in a con- 
stant temperature bath, the flow rate through N 
is controlled by the manometer M, . 
Branch II supplies dry air, desiccated by pas- 
sage through the drying tube D, prior to the 
filter F., while III feeds moist air, generated by 
dispersing the filtered air stream through porous 
carbon plates as fine bubbles within a thermo- 
stated water column H. Hereafter II and III join 
another, are filtered by the membrane filter F,, 
and then pass the system G2, S82, Vs, identical 
with that in branch I. Fy; assures the absence of 
particles in the flow when it enters the peripheral 
Venturi orifice, which joins the channel sections 
C; — C2. The adjustment of V2 and V; permits 
an accurate control of volume and humidity of 
the air flow when joining the aerosol in the Ven- 
turi tube. 
The channel C. guides the combined flow to 
the chamber C;, which contains a sensitive hy- 
grometer (membrane type) and wet-dry ther- 
mometers T. 
The A.S. A is connected by a wide tee-fitting 
either at the inlet or the outlet (not shown in 
Fig. 10) of C;. The assembly thus produces a 
dynamically stable aerosol supply which can be 
adjusted to a relative humidity varying from 
supersaturation to less than 10%. It also facili- 
tates the addition of traces of volatile components 
prior to, or after the generation of the aerosol. 
At 0.5 atm. pressure differential the flow rate 
through N is 5 lit/min, dispersing 40 mg/min 
water at T = 0° C, that is, 0.8% of the fluid ca- 
pacity of N. Hence the latter is sufficient to avoid 
significant variations of the concentration during 
operation for 5 to 10 min. 
For a 5% NaCl solution (0.855 n), the yield of 
