889 
and the second phosphorus pentoxide. All of the rubber tubing and rubber con- 
nections are of vacuum tubing and all joints are sealed with a solution of rubber 
in carbon disulphide. 
Manipulation of the apparatus.—After the apparatus has been shown to be 
tight, it is disconnected at A and the sample of coal weighed by difference into 
the iron tube B from a 40-centimeter bulb tube. By this means the inner sur- 
face of the iron tube is kept free from coal to a considerable distance from its 
open end. The apparatus is again connected as shown in the figure. The gas- 
holder (K) is completely filled with water and the stopcock closed. With the 
stopcock (H) in the position shown in the figure, the air is exhausted from the 
apparatus, The air is then exhausted from the tube connecting H and K_ into 
the apparatus and the apparatus again exhausted to a pressure indicated by 
the manometer (IF). In the meantime, the eight burners on the right in the 
illustration have been lighted and that portion of the furnace raised to a red heat. 
The water is next allowed to flow through the jacket, and the iron tube (B) is 
put in place in the furnace with the water jacket close to the furnace cover. 
As soon as the iron tube is red, the number of lighted burners is gradually 
increased and before long the distillation begins. As soon as the pressure within 
the apparatus is equal to the atmospheric pressure, the gas is turned into the 
gas holder (K). 
The rate of the production of the gas is regulated by the rapidity with which 
the number of lighted burners is increased. The best yield is produced with 
this apparatus when the rate of production is 100 to 200 cubic centimeters per 
minute. With the use of a higher temperature than that of the experiment, 
such as is used in a large gas works, this rate could be greatly increased. With 
this apparatus all of the distillation products must pass through the red-hot 
iron tube and therefore the quantity of tar is not increased at the expense of 
the gas, as is apt to be the case in the majority of miniature gas works. 
The water discharged from the gasholder is carefully measured as soon as all 
the gas has been driven off from the coal. When the apparatus has uniformly 
cooled to a known temperature the volume of gas is corrected to atmospheric 
pressure. 
Condition of conducting tests—No pyrometer was at hand, therefore 
it was necessary to construct one in order to read the distillation tem- 
perature. The apparatus was made in the following manner: 
An ordinary Schaffer & Budenberg pressure-gauge was fitted to a piece of gas 
pipe of 1 centimeter internal diameter about half a meter long, capped at one 
end, bent to a right angle in the middle and surrounded by a water jacket 
close to the pressure-gauge. The gas pipe was filled with mercury and the steel 
tube of the pressure-gauge with an inert gas (carbon dioxide) to prevent oxida- 
tion. When the mercury expands, this gas is compressed, the tube of the pressure- 
gauge straightens out, and the indicator moves over the gauge face. The usual 
scale of the pressure-gauge was covered with white paper and the pyrometer 
calibrated by determining its highest point by immersion in a crucible of melt- 
ing aluminium. For more accurate work, the calibration may be effected by 
using the following melting and boiling points: 
Aluminium 650° 
Sulphur 448°" 
Mercury 360° 
Naphthalene 218° 
Water 100° 
