Nitrogen Thermometer from Zinc to Palladium. 125 



Fig. 6. 



this case, for the glaze flows readily at these temperatures and 

 may make its way into the charge. With nickel and cobalt, 

 glazed Marqnardt tubes and also pure magnesia tubes of the 

 same size were used, but neither protects the element from 

 contamination. In palladium only the 

 pure magnesia tubes were used. 



Zinc, antimony, silver, gold, and 

 copper were melted in graphite cruci- 

 bles 27 mm in diameter and 80 mm deep 

 inside, and 37 mm in diameter and 

 100 mm high outside. The charge of 

 metal was from 45 mm to 55 mm deep. 

 Diopside and anorthite were melted 

 in small platinum crucibles 10 mm in 

 diameter and 18 mm deep, as described 

 and illustrated in the paper already 

 referred to.* Nickel was melted in 

 an unglazed Marquardt porcelain 

 crucible, lined with a paste con- 

 sisting of about 90 per cent A1 2 3 

 and 10 per cent MgO ; and also in a 

 Berlin " pure magnesia " crucible. 

 The charge was about 25 mrn in diam- 

 eter and 30 mm deep. Cobalt could not 

 be melted in the alumina lined cruci- 

 ble, as the metal penetrated through 

 the lining and attacked the porcelain. 

 It was, therefore, melted in a " pure 

 magnesia" crucible made by the 

 Konigliche Porzellan Manufaktur. 

 The material of these crucibles prob- 

 ably contains a small percentage of 

 silica. Palladium was melted in a 

 crucible made in this laboratory from 

 a specially pure magnesia made by 

 Baker and Adamson. The magnesia Fig. 6. The furnace in 



was first shrunk by heating to a tern- ^L^n^f d me J| al 

 •> f> . melting points were made, 



peratnre higher than that at which the showing the position of the 

 crucible was to be used, and was then metal with respect to the 

 made into a paste with water and a 

 little magnesium chloride, spun into 

 form, and baked. 



Particular details regarding each of 

 the substances used will now be taken up in the order of 

 temperatures, f 



*W. P. White, this Journal (4), xxviii, 477, 1909. 



f See, also, E. T. Allen, in paper of Day and Clement, loc. cit., p. 454. 



Am. Jour. Sci. — Fourth Series, Vol. XXIX, No. 170. —February, 1910. 

 9 



coil, the thermoelement (T) 

 and the arrangement (H) for 

 maintaining a hydrogen or 

 nitrogen atmosphere. 



their 



