AbstractsPhysics

The construction and operation of a vacuum ultracentrifuge are described. The duralumin rotor carries up to 96 cc of material for centrifugation. It is driven by a two phase induction motor supplied by a 1 kw audiofrequency generator, also described. The rotor is suspended from the armature, in vacuo, by a flexible stainless steel shaft. The whole rotating system is supported by an electromagnet. With this drive the rotor has been accelerated to 30,000 RPM in 13 minutes, with 1 kw power input. With 400 watts input and no attention from the operator, the speed remained within 3.1% of this figure for nine hours. By reversing the current, the system was brought to rest in & minutes, with only 300 watts applied. The centrifuge has been used for a preliminary study of the molecular weight of lignin dissolved in ethanol. The effects of high centrifugal fields on living cells are also described.