416 Mr. F. A. Waterman on an Improved Calorimeter . 



is somewhat similar in form to that designed by Prof. Henry 

 Crew *, consists of a copper tube H, about which is wound a 

 heating-coil of german-silver wire, insulated from the tube by 

 na/ row strips of asbestos-paper. This is enclosed within a 

 larger tube, and all is inserted within an ice-receiver I, the 

 space being packed with cotton to prevent convection- 

 currents. Water from the melting ice of the ice-receiver 

 escapes from the drainage-tube D f by means of a rubber-tube 

 connexion. The temperature of the outer wall remaining 

 constantly that of the melting ice, the fall of temperature 

 remains constant between the inner and outer walls as long 

 as heat is uniformly supplied to the inner chamber. This is 

 readily maintained by a constant electric current supplied to 

 the heating-coil, through the binding-screws B,from a storage- 

 battery of sufficient capacity having a variable resistance in 

 its circuit. The battery which has been used maintained a 

 normal electromotive force of 100 volts. The temperature of 

 the heater is readily maintained constant within y 1 ^ C. for five 

 or six hours, at any temperature desired for the conditions of 

 the work in hand, from -fy to -fa amperes of current being 

 required according to the temperature desired. The thermo- 

 meter, for the determination of the temperature of the heated 

 body, is supported by a cork inserted in the top of the tube H. 

 The bottom of the tube is closed by a cork, which is removed 

 to allow the solid to pass into the calorimeter-cup when 

 heated f. 



The method of making a determination of the specific heat 

 of a metal by means of this calorimeter is as follows : — 



The metal may be suspended in the heater in small frag- 

 ments, contained in a basket of fine wire gauze of known 

 specific heat, as employed by Eegnault ; or, if in the form of 

 sheet metal or fine wire, may be suspended in contact with 

 the thermometer-bulb by a thread of known weight. In the 

 case of metal of low melting-point I have cast thin cylinders, 

 slightly smaller in diameter than the calorimeter-cup, which 

 were so suspended in the heater that the bulb of the thermo- 

 meter was within the cylinder while heating. The thermo- 

 meter used is graduated into fifths of a degree Centigrade 

 scale, and hundredths of a degree may readily be estimated. 

 The metal is then maintained at the desired temperature from 

 one-half to three-quarters of an hour, according to the con- 

 ductivity of the metal used. 



* Philosophical Magazine, [5] xxxiii. 1892. 



t The heater, as now made, has a sliding cover which closes the 

 "bottom of the tube while the body is heating, and automatically opens as 

 the heater is turned around into position to deliver the heated body to 

 the calorimeter-cup. 



