191 2] William H. Welker 441 



stove with an 8 Inch top. A tin kettle, 4 inches deep and of the 

 same diameter as the stove contains paraffin oil. The tin kettle is 

 surrounded laterally by sheet asbestos Ke of an inch thick and a 

 layer o£ feit ^ of an inch thick. A metal cover, lined by asbestos 

 board, closes the top of the kettle. Through the metal top and 

 asbestos board are punched ^ inch holes for the tubes. 



The regulating panel consists of a one inch slate slab, 16 in, X 

 23 in., with the following electric apparatus mounted on it: an 

 ordinary electric bell ; a relay ; a resistance slab ; a rheostat ; a double 

 throw, double pole switch with two contacts on one side for one 

 arm; two binding posts for Hne connections; fuses; a double pole 

 switch ; three binding posts for the bath connections and three bind- 

 ing posts for the regulator connections. The wiring of the panel 

 and the constant temperature bath is shown in the accompanying 

 diagram (Plate IX). 



The constant temperature bath consists of a three-heat electrical 

 frying kettle 12 inches in diameter and 4 inches deep. It is about 

 three fourths füll of paraffin melting at a low temperature. The 

 heat insulation consists of an asbestos disk under the kettle. Later- 

 ally the kettle is coated successively with sheet asbestos Yiq of an 

 inch thick, feit wrapping %. of an inch thick, sheet asbestos Yiq of 

 an inch thick, sheet zinc and a feit coat % of an inch thick. On the 

 top there is a zinc cover lined by asbestos board. Holes }i of an 

 inch in diameter have been punched through the cover for the tubes. 

 When not in use these holes are filled with specially turned hard 

 wood Stoppers. Bulb test tubes similar to those previously described 

 are employed. 



MODE OF OPERATION 



The tubes with the urine and reagents® are placed in the pre- 

 liminary heating bath and the current is turned on. The switch 

 in the bottom of the bath is set so as to allow the maximum amount 

 of current to flow. When the temperature rises to about 100° C, 

 the switch is set to carry the bath to a medium degree of heat. 

 The temperature gradually rises and by the time it reaches 140° C, 

 the tubes are free from moisture. They are then ready for trans- 

 ference to the 164° C. bath. 



• Benedict : loc. cit. 



