New methods for the determination of hydrogen content of aluminum and its alloys: Part II. Rapid determination by the ni
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t e m p e r a t u r e and the s o u r c e s of s p u r i o u s h y d r o g e n production. The r e s u l t s obtained with this new t e c h nique and by the r e f e r e n c e hot e x t r a c t i o n method w e r e compared. 1) P R I N C I P L E OF THE METHOD AND A P P A R A T U S As in the hot e x t r a c t i o n method, 2'3 the s a m p l e to be analyzed is p r e p a r e d as a c y l i n d e r (0.9 cm in d i a m e t e r , 4.0 cm long, 7 g in weight) machined with g r e a t c a r e by d r y t u r n i n g - - t h e l a s t o p e r a t i o n being done with a diamond tool. To p r e v e n t i n t e r a c t i o n s with the atm o s p h e r e as much as p o s s i b l e , the machined s a m p l e is kept in methylketone until introduction into the app a r a t u s . The s a m p l e is put into an o u t g a s s e d g r a p h i t e c r u c i b l e housed in a q u a r t z tube with n i t r o g e n flowing at a t m o s p h e r i c p r e s s u r e . The inside of this f u r n a c e tube is i s o l a t e d f r o m the a m b i e n t a t m o s p h e r e by a nit r o g e n s c r e e n when the s a m p l e is introduced into the c r u c i b l e . This p r o c e d u r e e l i m i n a t e s the need for a lock s y s t e m . When the f u r n a c e tube is heated by induction, hydrogen e x t r a c t e d , by diffusion out of the liquid s a m p l e , is c a r r i e d by the n i t r o g e n flow to the d e t e c t o r which involves a conductivity cell ( k a t h a r o m e t e r ) a s s o c i a t e d with a n u m e r i c a l i n t e g r a t o r to d i s play the r e s u l t . The c o m m e r c i a l a p p a r a t u s , c a l l e d Ithac and manuf a c t u r e d by I n s t r u m e n t S. A.* has been d e s c r i b e d in * 15 Avenue Jean-Jaur6s 94201, lvry-sur-Seine, France.
detail elsewhere 8'9 and is outlined in Fig. i. Only the essential features of its four sections will be summarized: --an oven section --a carrier gas circuit at atmospheric pressure --a detector --a calibration system. The oven section, detailed in Fig. 2, consists of a quartz tube containing the crucible support. An exterVOLUME
6B, DECEMBER
1975-545
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Fig. 1--Working s c h e m e of the Ithac apparatus: H F = high f r e quency furnace, A = amplifier, MC = m a s s c o m p e n s a t o r , V F C = voltage frequency connecter, C = pump to a t m o s p h e r e .
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Fig. 2--Schematic drawing of the furnace section, (a) in w o r k ing conditions, (b) modified for m e a s u r e m e n t of sample t e m p e r a t u r e by thermocouple; c = closing flange, j = sealing g a s ket, g s = gaseous s c r e e n , r = cooling by w a t e r flow, uh and lh = upper and lower heads, so = coil, g = graphite crucible, s = sample, sc = support column,
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