338 BABCOCK. 



paper on steel tubes. Used only for changing the bath 

 temperature from one fixed point to another. 



e. Main Heater. 



Wound with nichrome wire on asbestos paper on wood. 

 Adjustable by means of external rheostats. Maximum 

 power 550 w-atts. Used to maintain bath temperature at 

 any desired point. Set so as to just allow the bath to cool. 



f. Regulating Heater. 



Wound with nichrome wire on asbestos paper on steel tube. 

 Adjustable by means of external rheostats. Maximum 

 power 50 watts. Switched on and off by an automatic 

 relay switch. 



g. Temperature Regulator. 



U tube of glass 3 cm. in diameter containing 500 cc. of 

 mercury. Stop-cock and reservoir at top of one limb, for 

 coarse adjustment. 1 mm. diameter capillary and reser- 

 voir at top of other limb. Contact needle of steel, with 

 well rounded blunt point. Screw adjustment on needle 

 for fine setting. 



h. Cooling Coils. 



Thirty feet of |-inch copper pipe coiled in the bottom of 

 tank and connected to the water mains. Needle valve for 

 adjustment. Used for regulation of temperatures below 

 35° C. and for rapid cooling of the bath from high tempera- 

 tures. 



i. Removable Cover. 



Cover arranged to be lifted by means of block and tackle, 

 carrying with it propellers, heating coils, temperature 

 regulator, and calorimeter. This was useful when it was 

 necessary to make repairs. 



IV. Laboratory Equations and Methods of Measurement. 



1. Laboratory Equation for Specific Heat at Constant 

 Volume of a Mixture of Liquid and Vapor. 



This equation, previously given, is 



_ 1 fSm 8HA 



