Double Helmholtz acoustic resonators, first proposed by Greenspan for
measuring the viscosity of gases, were tested with helium, argon, and
propane. Two different resonators were tested extensively with all thr
ee gases. For each of these instruments, the results for the viscositi
es of the three gases were consistent within +/-0.5% at pressures span
ning the range 25-1000 kPa. Without calibration, the viscosities deduc
ed from one viscometer were systematically 1% larger than data from th
e literature; the viscosities from the second viscometer were systemat
ically 3% larger than data from the literature. Ii the systematic diff
erences were removed for each viscometer by calibration with a single
gas at a single temperature and pressure, then nearly all the results
for both instruments would have fallen within +/-0.5% of the data from
the literature. In these viscometers, the test gases are in contact w
ith robust metal parts only; thus, these instruments are applicable to
a very wide variety of gases over a very wide range of temperatures.