BETWEEN THE VISCOSITY OF LIQUIDS AND THEIR CHEMICAL NATURE. 4I7 
cloth, and fitted to the filling bottle in the manner already described. The siphon 
was rinsed out by allowing a few drops of the liquid to be examined to run through 
it. It was then slowly emptied by putting the filling bottle under diminished 
pressure. When it is empty, and bubbles are just about to be drawn through it into 
the liquid in the bottle, the latter is put to air and the air current thus stopped. 
This method has always to be used in order to empty the siphon, and the process 
must be slow in the case of volatile liquids, otherwise evaporation takes place so 
quickly at the free end of the siphon that ice crystals form and the siphon has to be 
dried anew. 
The c|uantity of liquid necessary to carry out an observation is greater than can be 
contained in any one limb of the glischrometer. Instead, however, of filling the 
requisite amount into each limb by means of the siphon, time is saved, and risk of 
introducing dust is lessened, by filling liquid into one limb and by putting the other 
limb to reduced pressure, the requisite quantity of liquid being aspirated into it 
through the capillary tube. The method uniformly employed was to allow the siphon 
to extend to the bottom of the right limb, the filling bottle being attached to the 
pressure arrangement on the right side of the stand. The left limb of the apparatus 
was then connected by the rubber tube Q, fig. 3, to the pressure arrangement on the 
left side of the stand. The siphon was slowly set in action, and, after the liquid level 
had risen above the capillary, the left limb was j^ut under diminished pressure. It was 
necessary to allow but a small quantity of liquid to enter the left limb; when 
sufficient was introduced the pressure was brought up to that of the atmosphere and 
the filling of the right limb proceeded with. During this process, by lowering the 
glischrometer, the end of the siphon was kept just below the surface of the liquid; in 
this way only a short length of the outside of the siphon was wetted, and risk of 
introducing adherent dust minimised. When almost enough liquid had been intro¬ 
duced the frame carrying the glischrometer was clamped, so that the end of the 
siphon was at the height to be occupied finally by the liquid level. When the level of 
liquid had reached the end of the siphon the latter was emptied in the manner 
indicated. The volume of liquid to be introduced was found by trial; it was slightly 
more than was necessary for the purpose of observation when the liquid has the 
lowest temperature at which experiments were made. The quantity had not to 
exceed a certain limit, for, as will be seen presently, the traps T', T^, fig. 1, would 
thus be filled, and the observations would be interrupted before they had extended 
over the requisite range of temperature. It was also found convenient, in order to 
avoid the possible introduction of liquid into the trap during filling, to aspirate such 
a quantity of liquid into the left limb that the necessary volume of liquid was intro¬ 
duced into the glischrometer when the right limb was filled up to about the mark 
Mobile liquids run so quickly through the siphon that when the liquid has reached the 
desired level, before the action of the siphon can be reversed, so much liquid may 
enter the glischrometer that if the volume of the limb up to the trap is not consider- 
MDCCCXCIV.-A. 3 H 
