The electron diffraction investigation of the surface reactions involved in the flotation of sphalerite (ZnS) has been extended to the case of stibnite (Sb2S3). It has been confirmed that in some cases aqueous copper sulphate reacts with stibnite cleavage face to produce well developed crystallites of sulphides of copper (CuS and Cu1.8S), although in other cases an unidentified reaction product is also obtained. When the surface reaction product consists of very minute crystallites or is of amorphous nature, the action of aqueous xanthate thereupon leads to the formation of cuprous xanthate. The structure of the surface film of this cuprous xanthate coincides with that formed by the action of xanthate on sphalerite cleavage face activated beforehand by copper sulphate.
Transformation by life test of secondary-electron emitting surfaces of 2.5% Mg-Ag and 1.5% Be-Cu alloys are studied by means of electron diffraction. Oxidation products MgO and BeO which covered the activated surfaces are found to have been removed considerably from the surfaces after the test which reduced the secondary emission yield from initial values 4_??_7 to 2_??_4. It is also found that the oxide removed from the surfaces is deposited on the surfaces of nickel plates placed to face the emitting surfaces; the nickel plates produce diffraction pattern corresponding to MgO and Mg-metal in the case of 2.5% Mg-Ag and that composed of two halos coinciding with the strong Debye rings appropriate for BeO in the case of 1.5% Be-Cu. The substantial changes of the surfaces are considered to be the main cause of the damage of the secondary emission surfaces.
A new type electrometer, which has a very small effective capacitance, is described. Electrometer of this type was first devised by Y. L. Yousef and R. Kamel. By analysis and experiment, improvement has been made by adding a special damping electrode, amplifying the output and using a negative feed-back. Effective input capacitance of the order of 10-3 pf can be easily obtained. With this electrometer, a static potential distribution in space is measured with a moderately fast response comparable to an ordinary panel meter and a small current is measured with a detectability of 10-17 Amp. within a few minutes.
Accurate and rapid determination of determination of orientations of cubic crystal plates and, particularly, strips by the light-figure method has been worked out. Full accounts are given of the procedure for the determination, of the kind and number of applicable light figures or of accurately determinable orientation angles, of the stereographic representation of orientations, and of the accuracy in orientation determination with reference to actual examples of iron and silicon iron strip crystals. The kind and number of applicable light figures or of accurately determinable orientation angles depend on the crystal orientation to be determined, of which the relationship indicates that the perfect orientation determination can be made for most crystals for which the orientations of the plate normal lie close to the ,  or  axes. It is shown that orientations of single crystal strips of pure iron and silicon iron can be determined with an accuracy well within 0.5° by this method.