Fig. 18. Showing Cell ready for Assembly with Four Completed Cells in Background
For practical purposes the sensitiveness of a cell to light and its current generating properties are the only ones of value but other properties of these cells will be mentioned later. These may be developed by proper treatment and the results of experiments along these lines can hardly be foreseen with any degree of accuracy at the present stage of the development of the cells.
When satisfied that a cell is properly made and fairly sensitive it can be permanently sealed by pouring melted sealing wax around the edges and smoothing with a hot knife. A small sheet of paper should be pasted on the back of the cell with the more important characteristics marked thereon as well as the most suitable voltage. The terminal connected to the gold foil can be indicated by a positive (+) sign for convenience in properly connecting the cell into the circuit.
CHAPTER V
Applications of Selenium Cells
To go into a detailed description of the many applications of selenium cells is not possible in a work of the size of this. However a discussion of the manifold applications will point out in a marked manner the wonderful possibilities of a perfected selenium cell.
The use of selenium cells for photometric purposes was suggested by Clark on the occasion of the first announcement of the light sensitive properties of selenium. It was hoped that the selenium cell would remove the color stumbling block in measuring the brilliancy of light but to date a successful photometer using selenium has not been produced. The proposed method was to connect a selenium cell in series with a galvonometer properly calibrated and to allow the light to be measured to fall on the selenium cell, its brilliancy in candle-power or foot candles to be read direct from the scale on the galvonometer.
A cell of the Fritts type with a gold electrode would not be suitable for the purpose on account of it only passing the green rays but Fritts suggested that a number of cells be used, one with a silver foil electrode to pass blue rays and so on to include all the colors of the spectrum. Naturally the use of a perfectly transparent conductor on the surface of the cell would make it possible to use one cell for the entire range of color and with proper precautions a conducting liquid might solve the problem. This is worthy of attention and experiment.