394 CAIN AND cleaves: carbon in steel 



1450°. It was therefore thought that more accurate results 

 niight be attained if, after combustion had ceased, the oxides 

 were maintained in a state of fusion for some minutes. The 

 present work was carried out in order to test these ideas, by burn- 

 ing Bureau of Standards analyzed steel and iron samples — par- 

 ticularly the alloy steel standards — at temperatures ordinarily 

 employed but finishing at temperatures above the fusion point of 

 the oxides. The gas furnace and other apparatus shown in 

 figures 1 and 2 were employed. The combustion tube was of 

 platinum, with provision for water and air cooling of the ends, 

 as shown. When the flame from the blow-pipe impinged directly 

 upon the platinum without a protecting tube the temperature 

 attained was about 1520°, as indicated by a platinum, platinum- 

 iridium thermoelement and millivoltmeter. In some of the work a 

 protecting alundumtube was used around the platinum tube. This 

 however, was found to reduce the temperature more than was de- 

 sirable, largely because of reduced combustion space in the already 

 too small combustion chamber of the furnace used. During com- 

 bustion the steel was supported directly on the platinum boat; by 

 careful regulation of the rate of admitting oxygen and of the temper- 

 ature of the furnace the steel particles were coated superficially with 

 oxide before there was any danger of serious injury to the plati- 

 num by alloying; as soon as this coating was formed the combustion 

 could be finished at a moderate rate without danger to the boat. 

 The use of the alundum generally recommended as a lining mate- 

 rial for boats during combustion was found objectionable in these 

 experiments, because when it was employed the entire contents 

 of the boat could not be kept fused (the melting point of alundum 

 being about 2000°) and there was also some indication that addi- 

 tional carbon, not oxidized by prolonged ignition in oxygen at 

 1500°, was ehminated from the alundum when in contact with 

 fused iron oxide. Similar difficulties were encountered with other 

 supporting materials that were tried. The catalyzer following 

 the furnace was found absolutely necessary, since otherwise very 

 irregular results, sometimes several hundredths per cent low, were 

 obtained; tests with palladium chloride solution showed the pres- 

 ence of carbon monoxide in considerable quantity, when the 



