402 



ME. J. H. BRINKWOKTH ON THE SPECIFIC HEAT OF STEAM AT 



The arrangement of the apparatus is represented diagrammatically in fig. 4. The 

 gas, supplied from the mains, was led into the gas holder, R, from which it passed 

 through a Wolff's bottle containing sticks of KOH, into the limb, G, of the pressure 

 regulator and thence through the tube, B, to the burner. The steam generated in the 

 boiler was led through block tin tubes to the other limb, DS, of the regulator, thence 

 through E into the calorimetric apparatus and separator from which it passed down the 

 flow-tube to the condenser. 



Measurement of Electrical Energy. 



An insulated battery of 60-ampere-hour accumulators supplied the steady current 

 to the heating-coil through a standardised resistance of approximately the same value 

 and a rheostat. The method adopted for connecting the heating-coil in the circuit is 

 indicated in fig. 5. The four leads coming from the heating-coil are led into four 







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co 



C3 

 u3 



DC 



Hearing Coil 



cc. 



LU 



CO 



mercury cups, and the main current leads are similarly led into two other cups cut in 

 the same block of paraffin wax. With the aid of two copper connectors either pair of 

 leads may be made the " current-leads " to and from the heating-coil, the other pair 

 functioning as " potential-leads." By means of this arrangement it is also possible to 

 send the current through either pair of leads connected to one end of the heating-coil 

 and thus to investigate the heating effect 'due to the passage of the current through 

 the leads. The potential differences across the heating-coil, across the standardised 

 resistance and across a known number of cadmium cells in series, were obtained in 

 terms of the readings on a Thomson- Varley 2-dial potentiometer. If X,, X 2 and X 

 are the corresponding readings when the conditions are steady, the energy per second, 

 in watts, supplied to the heating-coil and used in heating the steam, is 



Where 



X 2 R 



R = resistance of the standardised coil. 

 e = E.M.F. of a cadmium cell. 

 n = number of cadmium cells employed. 



