the Roberts-Austen Recording Pyrometer 



73 



can be made with an accuracy of about 1 in 10,000. Very 

 good results are obtained by plotting the first differential of 

 the original curve : that is a curve the ordinates of which 



represent the values of -■- corresponding to the values of t 



indicated by the abscissae. 









Fig. 6. 









J 



t4 





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15 





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-> 



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£ 9 





or 9000 

 o 



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o 





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/ $b/ / 



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i 2000 





U) 









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or 





: iooo 





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&r TEMPERATURE 





-ZOtK^ 



-100" ^4f 



100" 200* 300' *O0' 500' 600° 700* 800' 900* I00O* 







.'/* 









/ /-IOOO 



AE 







// 



DATUM FOR TdT CURVE 





/ 





THERMOCOUPLE N°ll 



















/ 







This method can only be applied when a number of melting- 

 or boiling-points have been obtained, so as to enable the value 



