327.    BRAMLEY, A., AND BEERY, G. H.  Gaseous Cementation of Iron and Steel.  II>  Cementation With the Nitrogenous Vapor of Pyridine and Methyl Cyanide.  Iron and Steel Inst. Carnegie Schol. Mem., vol. 15, 1926, pp. 71-125; Chem. Abs., vol. 21, 1927, p. 1622. 

                  Object is to ascertain the amount and distribution of both C and N introduced when the bars were heated in an atmosphere of CO saturated at 18° with the vapors of either pyridine or MeCN.  The CO is passed up a column down which the liquid containing the vapor with which the gas is to be saturated is kept dripping through Cu gauze.  Otherwise the equipment is the same as in Part I.  The following factors were studied for CO saturated with C₅H₅N; (a) Rate of flow of gas stream; (b) period of cementation; (c) temperature of cementation.  MeCN is a more efficient cementing agent than C₅H₅N.  The condition of the bars after cementation was similar to that obtained with C₅H₅N.  The effect of increasing initial concentration of C was studied both for CO+C₅H₅N and CO+MeCN.  In the presence of N compounds, the importance of reversing the direction of gas flow is greater than with CO alone, as even in this case the cementation was at times more intense at the ends than in the middle of the bars.  Photomicrographs show that a characteristic feature of a case produced by a nitrogenous cement is the presence of a narrow zone near the inner edge of the case in which fairly deep etching shows needles.  The presence of N also reduces the amount of C in the steel of eutectoid composition and tends to preserve the Fe in the y state.