Abstract
Previous Micro-balances. - Brief reference is made to the instruments of Angström, Salvioni, Nernst, and especially to the all-quartz balance of Steele and Grant.
The Author's Micro-balance. - The instrument devised by the author, and here described, is also wholly of quartz. The knife-edge support is, however, replaced by a suspension consisting of a pair of quartz fibres. A magnetic arrestment is employed. Balance is obtained either (a) by an "air-weight," the upward displacement on a bulb being varied by varying the gas pressure within the enclosing case; or (b) by a "magnetic weight," involving the use of a measured electric current. The range of weighings depends on the size of beam: with one 5 cm. in length the maximum load is between 100 and 200 mg., and the setting can be made to within 10-7 mg.
The Stromberg Suspension. - Improvements in the construction devised by Dr. Stromberg are described, which obviate the formidable difficulties of manipulation that have hitherto discouraged workers from employing the instrument.
Investigations with the fibre-suspended Micro-balance. - A brief description is given of the following researches already carried out: - (1) The influence of temperature upon weight. This is an an extension of the work of Poynting and Phillips on this subject; (2) the volatility of silica; and (3) the susceptibility of diamagnetic bodies.
It is proposed to conduct investigations on the pressure of light, on the measurement of absolute temperature (based on an equation of Knudsen's), and on the loss of mass accompanying loss of energy.