Proceedings of the Indian Academy of Sciences - Section A

Raman, C.; Jayaraman, A.

doi: 10.1007/BF03052851pmid: N/A

Labradorite, the moonstones from Ceylon and Korea and other varieties of feldspar exhibiting iridescence have been investigated, and in all cases it has been found that such iridescence is the consequence of a diffusion of light within the material and not a true optical reflection. By a suitable technique, the diffusion haloes can be photographed and from their geometric positions, colour and angular dimensions, important conclusions can be drawn regarding the structures responsible for the iridescence. The plagioclase feldspars usually show two haloes geometrically related to each other according to the twinning law. The Ceylon and Korean moonstones differ in this respect; while the former invariably shows only one halo, the latter exhibits one, two or four according to the number of components present in the individual crystal.

Vasudeva Murthy, A.

doi: 10.1007/BF03052852pmid: N/A

Vasudeva Murthy, A.

doi: 10.1007/BF03052853pmid: N/A

Vasudeva Murthy, A.

doi: 10.1007/BF03052854pmid: N/A

Mehta, S.; Bharucha, N.

doi: 10.1007/BF03052855pmid: N/A

Advantage is taken of the solubility of cuprous oxide in hot saturated solution of potassium iodide in which metallic copper and cupric oxide are insoluble. The residual mixture of metallic copper and cupric oxide is then treated with acidified ferric chloride and the ferrous iron corresponding to the metallic copper titrated with dichromate or ceric sulphate.

Trivedi, A.; Divatia, A.

doi: 10.1007/BF03052856pmid: N/A

The unequal distribution of an electrolyte across a semipermeable membrane, in the presence of iron oxide sol is partly due to the establishment of (a) the membrane equilibrium and (b) hydration of micelles. Assuming that ten per cent. of the bound hydrogen ions are active in membrane equilibrium the hydration in the case of iron oxide micelles is calculated. It has been found that there are about 441 millimoles of water to one gram of iron oxide.

Patel, S.

doi: 10.1007/BF03052857pmid: N/A

The compounds RSO4.Sn(SO4)2 have been prepared. Conductivity measurements of the solutions obtained from RSO4.Sn (SO4)2 when compared with those of similar solutions prepared artificially show that the substances are double sulphates.

Thathachari, Y.

doi: 10.1007/BF03052858pmid: N/A

It is shown that ideally Bragg reflections can occur successively from two surfaces only if they form parts of the same sphere, a result shown to be sufficient (but not necessary) in an earlier publication. However, if the aperture radius and the size of the object are small compared to the radius of curvature of the reflecting surfaces (such that fourth and higher power of their ratios are less than (10−6), then the combination will work even with aspherical surfaces, provided the two reflectors are surfaces of revolution about a common axis and they are both concave reflectors having the same vertex radius of curvature and are separated by a distance equal to twice this radius. If a combination of two such mirrors are used, andN multiple reflections obtained with them, then the optical path is reduced appreciably (approximately as 1/N) and the spherical aberration is also decreased (being proportional to 1/N) for large magnifications. The resolving power of such a combination should be of the order of 50 °A. A combination of X-ray mirrors in the form of an X-ray microscope has, therefore, distinct advantages and it appears that the problem of realising such a unit in practice is worth investigating.

Doss, K.; Saraswat, H.

doi: 10.1007/BF03052859pmid: N/A

A detailed study has been made of the kinetics of inactivation of invertase at 25°C. in acid media. The results indicate the existence of two processes, one of them being very fast and coming up at comparatively high pH values and the other coming up at lower pH.

Subba Rao, K.; Wadhawan, S.

doi: 10.1007/BF03052860pmid: N/A