On the viscosities of the hydrogen halides

The measure of agreement between the values of the atomic diameter obtained from W. L. Bragg’s crystal measurements, and those deduced from viscosity data and the Kinetic Theory, has recently been demonstrated by A. O. Rankine for the halogen gas molecules, in which the two atoms are of equal size. The mathematical treatment by which the mean collision area is obtained, can be extended to molecules compounded of two unequal atoms such as those of the hydrogen halides, and the present viscosity experiments were undertaken with a view to affording a test of the further theoretical investigation of Prof. Rankine.General Method of Procedure . The chemical activity of these gases limits the possible modes of measuring the viscosity, and is the cause of the chief difficulties of the experiments. The method chosen was that of the transpiration of the gases through a capillary tube, the dimensions of which were obtained by transpiring air. The viscosity of air is now sufficiently well known to justify its use for this purpose, and the uncertain measurements of the length and diameter of the tube are thus avoided.