J. Eggert

The initiation of explosion by light

By means of a tabular compilation it is shown that a large number of explosion primers can be caused to detonate by brief irradiation with the sparks from energetic electric discharges. Whereas it could be found that in the case of nitrogen iodide there is a weak photochemical effect (5 to 10%) in all other cases initiation is due to the sudden heating of the compounds, therefore a photothermic effect. A number of proofs can be given for this phenomenon. In the case of silver nitride Ag3N, it is even possible to prepare layers so. thin that the ignition (with correspondingly increased energy) can be effected in the area of the incident radiation, but cannot be caused to spread to other areas of the layer. These layers are suitable for the making of prints. With equal layer-thickness the energy required for the initiation increases with the duration of the igniting spark.

Die Stabilität des latenten Bildes und des photolytischen Silbers

An fruheren und neueren Beispielen wird dargetan, daβ das latente Bild und das photolytische Silber, dies sogar hinsichtlich seiner Struktur, eine relativ grose Bestandigkeit gegenuber gewissen chemischen Eingriffen aufweisen.

Die wichtigsten Verfahren der Farbenphotographie

In the early days of photography daguerrotypes were stained with specific pigments (Isenring).Lippmanns “interference procedure”, working with the pure colours of the spectrum is of great interest theoretically, but cannot be used practically. Only after the division of the visible spectrum into 3 regions: 400–500 mµ (blue), 500–600 mµ (green) and 600–700 mµ (red) and the discovery of sensitizers byVogel did the modern colour photography become possible for practical purposes.Ducos du Hauron recommended several different ways for colour photography based on that principle and even followed some of them up by himself; however, only a few have proved valuable. The method of microscopic-coloured mosaic filters and the lenticular film method work with an additive process. For coloured prints in books and journals one first produces separate exposures from the original by the aid of filters that are transparent in the before-mentioned regions of the spectrum. By means of these separate negatives the print is produced with printing stains that are complementary to the filter stains, i.e. yellow, magenta and cyan. The Technicolor-method now widely used in cinematography works under similar conditions. Beside that only the method of colour development in different varieties and ways of application is in use today.