398 



WRIGHT: ELECTRICAL GONIOMETER FURNACE 



which temperature the light of the furnace becomes relatively 

 intense and the measurements are correspondingly less satis- 

 factory. 



The furnace fits as an attachment on the Goldschmidt two- 

 circled goniometer (fig. 1, ^). It consists of two flat disks of 

 alundum (7 cm. in diameter and 5 mm. thick) on one side of 

 which a spiral of 1.75 mm. pitch is stamped ;2 into its grooves 

 platinum wire 0.4 mm. thick is wound and then covered with a 



Fig. 3. Top view of furnace after water jacket Ai has been removed. Figure 

 3a shows arrangement of alundum segments, a, b, c, of asbestos ring segments 

 d, e, f, of crystal holder H, of crystal /, and of thermoelement wires T, in case 

 the furnace is used for measuring interfacial crystal angles. The arrows indicate 

 the paths of the rays from collimator to crystal and then to telescope of the go- 

 niometer. In figure 3b, the arrangement is sketched for the case of the measure- 

 ment of the refractive index of the prism P by the minimum deviation method. 

 The letters have the same significance as in figure 3a. 



thin layer of alundum cement and baked at 1200° to 1300°C. 

 These disks are backed by magnesia powder and mounted in 

 hollow cylindrical water jackets (fig. 2) Their edges are shielded 

 from direct contact with the water jackets by asbestos wool pack- 

 ing. The details of construction are evident from figures 1 and 

 2. Segments of alundum 10 mm. thick and of the shapes indi- 

 cated in figure 3, a, b, c, are placed in position on top of furnace 



2 Made on special order by the Norton Company of Worcester, Mass. 



