W. THOMPSON'S CALORIMETER. 37 



were thrown to the coal, and it soon kindled. The oxygen 

 flowed in by g and e. When combustion was well under way 

 and had reached the lower portions of the coal, g was shut off 

 and /opened. 



Schwackhofer obtained complete combustion of the sugar- 

 carbon and coal, with no formation of black, and no residue of 

 coke. 



The gaseous product of the combustion was generally of 

 the following composition : 



Carbonic acid 50 to 60 percent; 



Carbonic oxide 1.2 to 0.3 " " 



Oxygen 10 to 15 " " 



Nitrogen 30 to 40 " " 



arising principally from the fact that to keep up the normal 

 pressure the combustion-chamber was in communication with 

 the open air. The cinders were weighed after each test. 



This apparatus should give exact results, but its use is 

 complicated. The long duration of the test requires impor- 

 tant corrections for influence of external heat, and it needs 

 several thermometers. 



w. THOMPSON'S CALORIMETER. 



W. Thompson devised a calorimeter in which the com- 

 bustion is started by a jet of oxygen, but the waste gases in- 

 stead of passing through a coil bubble up through the water 

 of the calorimetric bath. In this apparatus the uncombined 

 gases are naturally neglected. (See Fig. n.) It is an appa- 

 ratus, as the inventor says, not intended for scientific re- 

 searches, but for handy use of mechanics or " for popular use." 



a is a galvanized-iron gas-holder containing oxygen ; b, a 

 stop-cock regulating the flow of water to this holder; d, stop- 

 cock for gas ; e, rubber tube ; f, level-gauge ; g, pressure- 

 gauge; h, bell-glass covering the platinum crucible k, in which 

 the coal is burnt ; / is a support of earthenware suspended 



