The interstellar extinction law from 1 to 13 microns

Measurements from 1 to 13 μm are reported for ο Sco and for stars in the galactic center. The interstellar extinction law toward these sources and toward VI Cyg No. 12 is the same from 1 to 13 μm. An improved estimate of the extinction law beyond 3 μm is presented, including an improved ratio of total to selective extinction, R ≈ 3.09±0.03, and an improved ratio of total extinction to optical depth in the 10 μm silicate absorption, A<SUB>v</SUB>/τ<SUB>Si</SUB> = 16.6±2.1.