The Smelting of Titaniferous Iron Ores 41 



in these experimental runs has been from 30 to 60 kilowatts, at 60 volts. 

 The furnace is heated thoroughly before charging ore by means of 

 passing the current through a resistant bed of charcoal between the 

 electrodes. This preliminary heating takes several hours, even when 

 the furnace is dry and warm from previous operation. When the fur- 

 nace walls are sufficiently hot, ore, charcoal and flux, mixed in appro- 

 priate proportions, are fed between the electrodes, slowly enough to 

 prevent any undue chilling of the crucible. Until a fluid bath of resist- 

 ant slag is formed, it is usually difficult to regulate the current passing 

 through the furnace. When the charge has been completely smelted 

 (usually a matter of three or four hours with 100 lbs. of ore), the metal 

 and slag are poured into pots or molds by tilting the furnace. 



Pryometer 



The temperature of the bath of metal and sfag has been determined 

 by sighting on the lining of the furnace immediately after pouring, with 

 an opt'cal pyrometer. As the volume of slag and metal is small, it 

 chills on leaving the furnace, and no reliable readings of temperature can 

 then be obtained. The instrument used is the F. and F. optical pyro- 

 meter of the Scientific Materials Company. It is a modification of the 

 Wanner pyrometer, which makes use of the principle that "when the 

 temperature increases, the wave length of every mono-chromatic radi- 

 ation diminishes in such a way that the ptoduct of the temperature and 

 the wave length is constant."^ By means of an arrangement of lenses 

 and Nicol prisms, red light from a six-volt incandescent lamp is viewed 

 through an eye-piece side by side with the same red light from the hot 

 body whose temperature is to be measured. A Nicol analyser in the 

 eye-piece is rotated to make the two reds alike, and this angular move- 

 ment, indicated on a graduated circle, is marked to correspond with 

 degrees of temperature. The small electric lamp in the instrument is 

 calibrated occasionally against a flame of standard amyl acetate, using 

 a resistance to vary the current from the storage battery. This method 

 of measuring high temperatures is said to be accurate if reasonable pre- 

 cautions are observed. 



Analysis 



As no existing method of complete analysis was found suitable for 

 ores and slags high in titanium, the investigation had to be preceded by 

 the working out of such a method. As the result of several months of 

 analytical research on the part of W. L. Goodwin and A. F. G. Cadenhead, 

 existing schemes of analysis were modified and adapted to this purpose 



^Burgess — "Measurement of High Temperatures." 1912, p. 315. 



