CAIN AND cleaves: CARBON IN STEEL 



393 



CHEMISTRY. — The determination of carbon in steels and irons 

 by direct combustion in oxygen at high temperatures. J. R. 

 Cain and H. E. Clea\^s, Bureau of Standards. 



In determining carbon in steels by the method of direct com- 

 bustion in oxygen it has been the practice at the Bureau of Stand- 

 ards to pulverize and reburn the oxides — repeatedly, if necessary. 

 Although particles of metal are seldom found in the oxides, addi- 

 tional carbon is generally obtained by this method; in some 

 samples as much as 0.02 per cent. With the idea that such carbon 



Fig.l. Details of Apparatus 



Ci and C2, porcelain tubes filled with copper oxide and wound with nichrome 

 wire for heating; T, tower filled with stick KOH; F, gas furnace; A, tube for 

 air cooling; M, Meyer bulb ; S, soda lime guard tube. 



was probably retained as difficultly oxidizable carbides, it was 

 thought that alloy steels contining such metals as chromium, 

 titanium, and tungsten, or high percentages of silicon, all capable 

 of yielding carbides very resistant to oxidation, would be especially 

 subject to this source of error. Additional weight was given to 

 this view by results reported from laboratories specializing in the 

 analysis of such alloys, and obtained by combustion at tempera- 

 tures higher than those usually recommended. 



As combustions are ordinarily effected, the mass of oxides is 

 kept fused for only a very short time, if at all, after the metal 

 has ceased to burn, inasmuch as the temperature usually main- 

 tained in the furnace is 950° to 1100°, whereas the melting points 

 of the oxides obtained by us during combustion^ were near to 



^ Determinations made at this Bureau indicate that the oxides, when melted in 

 oxj^gen, gradually absorb that gas with rise in melting point. This matter will 

 be discussed in the more extended paper to be published by us elsewhere. 



