Introduction: "The carrier (pyroelectric) concentration method is commonly used in the spectrographic analysis of plutonium metal. This report describes work which lead to substantial improvements in accuracy, precision and ease with which the analysis is made. Included are data from analyses of plutonium metal by the original and the improved carrier methods, and the cupferron extraction method."

An experiment now in progress should give some accurate information about the thermal neutron absorption cross section of carbon 12. This report outlines and summarizes this experiment and analyzes it to determine the main sources of error and the probably error in the final result.