A recently-developed neutron absorption cell measures the thermal neutron absorption cross sections of formation brines (E ). This is one of the parameters needed for interpreting pulsed neutron decay logs. Generally, E is estimated from the salinity of the brine. ~ometimes it can be measured in a large tank with a logging tool, but this requires several hundred gallons of the brine. With the neutron absorption cell, this measurement can be made on a sample as small as one gallon, with a precision of 0.1 percent, in less than 5 minutes.