190 BELL SYSTEM TECHNICAL JOURNAL 



cedures have been devised which can be used satisfactorily for certain 

 gases. A method of determining oxygen, nitrogen, and hydrogen in 

 ferrous alloys, developed by Jordan -' and his co-workers, and by 

 Oberhoffer,^^ is now widely used. 



In the method of Jordan, the samples to be analyzed are melted in 

 vacuum in a gas-free Acheson graphite crucible. The liberated gases 

 consist of carbon monoxide, nitrogen, and hydrogen. The carbon 

 monoxide is formed by interaction of oxygen (or oxides) from the 

 metal with carbon from the crucible. The nitrogen, which may 

 originate from dissociation of nitrides, is evolved from the metal 

 without chemical reaction with the crucible. The form in which 

 hydrogen exists in the metal is unknown. These gases are pumped 

 away from the melting compartment and collected for analysis. The 

 carbon monoxide and hydrogen are oxidized to carbon dioxide and 

 water, respectively, by passing them over heated copper oxide, and 

 their quantities are determined by absorption in suitable absorbents. 

 The residual gas, nitrogen, is determined by a volumetric method. 



The Jordan apparatus with some modifications,^^ as shown in 

 Figs. 2 and 3 is used at Bell Telephone Laboratories. The most 

 important change is in the method of determining the weights of 

 carbon dioxide and water formed during the analysis. In Jordan's 

 apparatus, the absorbents for carbon dioxide and water are contained 

 in weighing tubes which must be weighed along with the absorbent 

 and the absorbed gas. In most experiments, the weight of gas 

 absorbed is only a few milligrams and an elaborate technique is 

 required, therefore, to weigh this small quantity when contained in a 

 tube whose weight is relatively large. In the new modification, in 

 order to minimize errors in the measurement of weight, and to simplify 

 the technique required, a quartz spring balance has been substituted 

 for the weighing tube. The absorbent for the gas is contained in a 

 light glass basket attached to a quartz spring. The extension of the 

 spring is measured with a cathetometer and the weight of gas absorbed 

 determined from calibrations. Springs are made in various sizes so 

 that one can always be found to fit the range of weights it is necessary 

 to measure. 



^' Jordan and Eckman, U. S. Bureau of Standards ScicJitific Paper No. 514 (1925). 

 Jordan and X'acher, U. S. Bureau of Standards, Jour, of Research, 7, 375 (1931). 



*'' Oberhoffer, Archiv fiir das EisenhiiUenwesen, p. 583, March, 1928. 



^' These modifications were developed by Mr. E. S. Greiner who will describe 

 them in the near future in a paper giving the complete details, together with a 

 critical study of the method. 



