Abstract
AbstractThe magnetically supported vacuum‐type equilibrium ultracentrifuge previously described has been improved and used for the measurement of the molecular weights of a number of substances. The modifications include an electric motor drive which accelerates the rotor to operating speed. The rotor coasts freely during the sedimentation, and the operating speed may have any desired value from a few revolutions per second to the maximum safe speed of the rotor. Improvements have been made in the ultracentrifuge cell, and both white light and monocromatic light fringes can be used interchangeably in the interferometer. These modifications make possible the determination of the molecular weight quickly either without waiting for equilibrium to take place or after equilibrium has been established. The overall precision is the order of one part in a thousand for the centrifuge measurements themselves. Molecular weight data are given for a number of substances, including sucrose, ribonuclease, and insulin. The application of the centrifuge to the determination of molecular weight distributions is discussed.
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