170 
DR. E. P. PERM AN, DR. W. RAMSAY, AND ^[R. J. ROSE-INNES. 
between 100° and 130°; bromobenzene, givdng a range of 130° to 150°; aniline, 
of 160° to 180° ; and quinoline, of 180° to 200°. Observations were always made 
at even temperatures, the pressures being adjusted so as to cause the liquid to give 
oh vapour of the temperature recpired—100°, 110°, 120°, &c,, up to 200°. 
The method of filling the tube also requires description. First, as regards the 
powder introduced to show the wave-lengths of the vibrating gas. In air and similar 
gases, lycopodium dust gives the most distinct figures ; but it is a resinous substance, 
and hence it was not possible to place it in contact with ether. After many trials of 
magnesia, alumina, precipitated silica, &c., a quantity of somewliat impure silica was 
prepared, by fusing glass with carbonate of sodium and potassium, and treatment 
with hydrochloric acid ; this gelatinous silica was not very well washed, but was 
dried in a somewhat Impure state, containing a trace of common salt. It was 
ignited, and fritted together to rough lumps. These were powdered in an agate 
mortar, and sifted through gauze. The small fragments of microscopic size were 
approximately spherical, and fiowed easily, not adhering to each other. Pure silica 
is too dusty ; sand is too large-grained, or, if powdered, too angular; to obtain the 
best results the grains should be round and not too small. 
A sufficient quantity of such sand was introduced into the experimental tube ; its 
open end, A (fig. 3), was then sealed to a bulb, B, of the form shown in the woodcut; 
and the tube at the seal was drawn out into a wide capillary, C. Ether was placed in 
the bulb, and the open end, D, was then ccmnected with a water-pump, and the bulb 
was exhausted. The ether began to boil and expelled air from the bulb. By admitting 
air, ether entered the experimental tube, A ; and the hidb was again exha,usted and 
then sealed at E. The amount of air was then reduced to that dissolved in the 
liquid ether. The experimental tube was next warmed, so as to boil the ether it 
contained ; the vapour rushed up, driving pistons of liquid before it, and condensed 
in the bulb, which was artificially cooled. After about ten minutes, all possible air 
had been expelled from the tube into the bulb. On gently warming the bulb, B, 
and cooling tlie tube, A, liquid ether entered, and the absence of air was certain, 
inasmuch as the ether closed up rapidly and completely, no trace of a bubble being 
left in the tube. If even a small bubble were left, dissolvino’ in the etlier on its way 
up tlie sloping tube, the operation was repeated. The silica during this operation 
usually found its way into the bulb D (fig. 2) at the end of the experimental tube. 
The tube was again warmed so as to expel ether. And here arose a difficulty. 
It was necessary to guess at the quantity of ether which was required. Usually, 
the experiments were adjusted to suit the particular quantity which accidentally 
remained. But with a little practice it was found possible to leave in the tube 
approximately the amount required. The capillary junction, C (fig. 3), between the 
experimental tube and the bulb was then sealed, leaving a thin tail of glass. The 
silica was then sliaken out of tlie bulb of the experimental tube (see fig. 1, G, and 
fig. 2, B) into (he tube itself, and distributed along its length as evenly as possible 
