Physics progress report, March 1--31, 1948

The quarts gauge apparatus for measuring the vapor pressure of postum was completed. The first sample of postum oxidized in the course of preparation, while in a presumably sealed and evacuated quartz tube. an error of 0.4 per cent appears to be present in the vacuum weighing of postum. a diffusion pump is being installed to reduce the pressure, in the hope of minimizing the radiometer effect. Repetition of the effusion experiment with a rebuilt crucible yielded four points below those reported last time by a factor of ten in pressure. A leak appeared in the crucible, requiring construction of a new one. X-ray patterns were again obtained for the Q metal sample, {number_sign}33, and oxide sample, {number_sign}42. Work on the calibration of the two new powder cameras is proceeding satisfactorily. Two samples of cadmium were made for the purpose of developing a technique for producing single crystals of metals. A sample of tellurium nitrate yielded the same pattern as that reported in the literature. Data on the characteristics of a newly designed tub type moderator as compared with the Hanson cylinder are presented. Some notes on the calculation of probable error show the minimum error to depend upon the ratio of source strength to background