Aug.,
THE JOL-R.\7d;AL OF I N D U S T R I A L A N D EiVGI,VEERIAVG CHE-ZIISTRk’.
1911
per minute and have none of the solution splash out, at the same time having enough air passing into the
595
ELECTRIC TUBE FURNACES WITH CALORITE RESISTERS FOR THE LABORATORY BY SAMUEL A4.’ h C K E R .
n
Wire-wound resistance furnaces have now come into general use for electric furnaces in the laboratory and fill a place that perhaps no other heating appliance is capable of. I n our experience we have tried several types of resisters, starting with platinum and some types of chromium-nickel alloys. Platinum, besides being expensive, is not ideal for resister purposes, as the life is limited and repairs are b y no means easy. Nichrome has shown a tendency t o crystallize and in this condition breaks under slight strain. The General Electric Company manufactures a resistance material known as calorite, some of which was kindly furnished to us, and with it several furnaces were constructed which have given great satisfaction. Calorite is a n alloy of nickel, iron, chromium, and manganese, and has a melting point of 1550’ C. and a low temperature coefficient. The material as furnished was in the form of tape or ribbon 2.38 mm. (0.094”)wide and 0 . 2 4 mm. (0.008”) thick. It has a resistance of 0.878 ohm per foot and is fairly soft, which is increased by annealing a t a low red heat in the air just as platinum wire can be annealed. Oxidation, when heated in the air, is merely superficial even a t quite high temperatures, and there seems to be no tendency to crystallize. The alloy cannot be used in contact with silica a t high temperatures, and the furnaces were therefore constructed with a view t o this property. Three furnaces were made as follows: No. I was designed for tube-heating having a short heating zone which will bring t o an even temperature the average size combustion boat. The general construction consists in winding the resister on a porcelain combustion tube, surrounding it with chemically pure alumina which is held in a n asbestos tube and then surrounding the whole with asbestos wool packed between the inside asbestos tube and the outside container which is also of asbestos. Figs. I and z are drawings of No. I furnace. A is the porcelain tube of Royal Meissen ware glazed inside, but not on the outside, 4 5 7 mm. (IS”) long with internal diameter of 25.5 mm. (I~’), outside diameter 30.5 mm. ( 1 3 1 1 a ” ) . There were collars a t R
n
into the bottle. STANFORD UNIVERSITY, May, 1911.
\
Fig. I. Read a t the May meeting of the New York Section of the American Chemical Society. 1
596
T H E JOURA’AL OF I N D U S T R I A L A N D ENGINEERI;L’G C H E M I S T R Y .
each end of the tube which serve no purpose, but the tube would have been too short had they been removed. These collars had a diameter of 51 mm. (II/~”) and a length of 2 5 . 5 mm. (I”). The tube projected out of the furnace 95.5 mm. (33/,”) at each end, leaving a n available winding space of 2 6 7 mm. (IOI/
