G08 
DR. T. S. HUMPIDGE ON THE ATOMIC WEIGHT OF GLUCINUM. 
casing of brass wire gauze used to contain the substances was greater than that of the 
substances themselves. As far as possible these errors have been avoided in the 
following modification of Regnault’s method. The apparatus consists of two parts— 
that for raising the substance to a high temperature, and the calorimeter proper. 
The heater is an annular brass vessel of 32 millims. internal and 64 millims. external 
diameter, and is 115 millims. high (Plate 45, fig. A.). Its lid screws on firmly and is 
made steam-tight by indiarubber packing, freed from sulphur by previous boiling in 
caustic soda. Three tubes pass through the lid of the heater, the central one carrying a 
thermometer (T 2 ), which gives the temperature of the interior air bath, while the other 
two enclose platinum wires connected with the arrangement for supporting the 
substance and for allowing it to fall into the calorimeter at the correct instant. All 
connexions in the lid are made as air-tight as possible to prevent any upward current 
of cold air into the heater. The substance is supported in a small platinum capsule 
(B) attached by a hinge to one of the platinum wires referred to above, and this 
capsule is held in a horizontal position by the second platinum wire, the end of which 
is bent at right angles to its length. To the upper end of this platinum wire is fixed 
a strip of wood, so that the wire can be easily turned through a small angle, the catch 
released, and the substance allowed to fall into the calorimeter. The heater is 
completely covered by a double coating of thick baize, and is placed in a wooden box 
(not shown in the figure). In the bottom of this wooden box is a small slider (C) 
which is connected with an electro-magnet and can be opened or closed at will. Two 
tubes (D, D) connect the annular space of the heater with a boiler containing water, 
placed on the other side of a tin screen, and with the air. The whole heating arrange¬ 
ment stands on a larger box (E) open at one side and with a long base board, and this 
again is supported on a suitable wooden stand. 
The calorimeter itself (F) is a small thin platinum vessel of 50 millims. in diameter and 
60 millims. in height, and containing therefore when full about 100 cc. It is furnished 
with an agitator of two discs of thin perforated platinum, soldered with gold to two thin 
platinum wires, one of which terminates about 15 millims. below the lid of the brass 
casing in a hook. To this hook a silken string (G) is attached, which passes over 
pulleys and is kept stretched by a small weight. The two discs of the agitator have 
perforations at one side for the bent thermometer (T 2 ), which gives the temperature of 
any liquid contained in the calorimeter. The advantages of using platinum for 
calorimeters have been pointed out by Berthelot. It always remains bright and of 
constant weight, and from its low specific heat corresponds to a very small equivalent 
of water. The weight of my calorimeter and agitator is 74 - 40 grammes, and its water 
equivalent 2’41 grammes, but it might have been made very much thinner. The 
calorimeter stands on three boxwood cones in a brass casing, which is fixed by three 
pieces of cork to a sliding board. This brass casing is 85 millims. high and 77 millims. in 
diameter, and its movable lid is furnished with a small slider which can be opened or 
closed by two iron armatures working in the two solenoids (H and H) placed one on 
