


IMPROVED FORMS OF BOMB CALORIMETER. 203 
and to conduct an electric current. Of these two wires one, I, 
is screwed into the cover; the other, H, passes through a cont- 
cal hole in the cover. 
The method of insulating the wire (H) which conducts the 
current through the cover of the bomb at M, Fig. 2, is shown 
in Fig. 3. Inthe bomb cover, a section of which is shown at 
A, is a conical hole. ‘The largér end of the hole is on the 
inside of the cover. Into this hole fits a German silver cone 
(B). ‘This is practically an enlargement of the small rod (C) 
which projects above the cover and serves for the electrical 
connection. ‘The platinum wire (D) is gold soldered into the 
lower end of the cone, thus making a continuous conductor (C, 
B, D). ‘To insulate this conductor a piece of rubber tubing is 
fitted over the cone. The rubber tube is long 
enough so that it can be stretched out, as the 
cone (B) is drawn into the cover; the surplus 
rubber tube is then cut off at FE, and over the 
rod (C) is placed the hard rubber sleeve (F), 
and the nut (G) is tightened down until the 
conductor (C, B, D), is firm in the cover. To 
prevent the burning of the rubber insulation on 
the inside of the bomb, and to prevent leakage 
of current due to the conductivity of the nitric MetHop oF IN- 
acid formed in the combustion, a mica disk (H) — SUPATION: 
is placed over the platinum wire (D), and held against the 
platinum lining of the cover by the platinum nut (I). If a 
little space is left at the large end of the cone not filled by 
the end of the rubber tubing it is filled up with a mixture of 
fine asbestos fiber and shellac, which is allowed to dry before 
the mica disk (H) is secured in place. 
Near the lower end of H is a platinum wire (N, Fig. 2), bent 
in the form of a ring to hold the platinum capsule, and coiled 
about the wire, to which it is held by a screw. When a com- 
bustion is made the two platinum wires are connected by a very 
fine iron wire which passes over the crucible. The part directly 
above the substance to be burned is bent into a spiral, thus 
furnishing a larger quantity of iron to be ignited and, falling, 
to ignite the substance in the crucible. 
Three small pins on the bottom of the bomb, of which 
two are shown in the diagram, support it when standing 

