Olszewski's as a chemist, physicist and expert of low temperatures; the first scholar who liquefied nitrogen and oxygen. In addition to the discovery of a method of hydrogen liquefaction and constructed machinery for that purpose, which enabled him to reach the then-lowest world temperature of -225 C.
This website discuss of the process of the liquefaction of gases in which Sigmund von Wroblewski and Karol Olszewski were able to produce large quantities of liquid oxygen "boiling quietly in a test tube." Also in that same year, they used liquid oxygen to liquefy nitrogen at 77K.