  The first loading of gadolinium (Gd) into Super-Kamiokande in 2020 was
successful, and the neutron capture efficiency on Gd reached 50\%. To further
increase the Gd neutron capture efficiency to 75\%, 26.1 tons of $\rm Gd_2(\rm
SO_4)_3\cdot \rm 8H_2O$ was additionally loaded into Super-Kamiokande (SK) from
May 31 to July 4, 2022. As the amount of loaded $\rm Gd_2(\rm SO_4)_3\cdot \rm
8H_2O$ was doubled compared to the first loading, the capacity of the powder
dissolving system was doubled. We also developed new batches of gadolinium
sulfate with even further reduced radioactive impurities. In addition, a more
efficient screening method was devised and implemented to evaluate these new
batches of $\rm Gd_2(\rm SO_4)_3\cdot \rm 8H_2O$. Following the second loading,
the Gd concentration in SK was measured to be $333.5\pm2.5$ ppm via an Atomic
Absorption Spectrometer (AAS). From the mean neutron capture time constant of
neutrons from an Am/Be calibration source, the Gd concentration was
independently measured to be 332.7 $\pm$ 6.8(sys.) $\pm$ 1.1(stat.) ppm,
consistent with the AAS result. Furthermore, during the loading the Gd
concentration was monitored continually using the capture time constant of each
spallation neutron produced by cosmic-ray muons,and the final neutron capture
efficiency was shown to become 1.5 times higher than that of the first loaded
phase, as expected.
