Hellma Cells are manufactured from different types of glass. The most important criterion for the choice of a particular type of glass ist the spectral range for which the cell is intended. Basically, we differ between two ranges of material:
Quartz consists exclusively of silicon dioxid (SiO2)and shows some remarkable properties:
Common criteria for all types of Optical Glass are:
The Hellma precision cells are manufactured from glass and quartz and possess all the benefits of this material. Hellma generally recommends that cells are cleaned and dried immediately after use and returned to their storage cases. Do not keep the cells in the open in a corrosive atmosphere, and do not leave the polished windows in contact with liquid over long periods of time. Both conditions could lead to formation of deposits or stains and could render the cells unusable.
To avoid scratches on the precision-polished windows, the cells should never come into contact with objects made of hard materials like glass or metal.
Use caution when handling Cells with Stoppers: Cells that contain liquid and are sealed with stoppers may crack as a result of increased inner pressure. The most common cause of such a pressure increase is the expansion of the liquid within the cell due to an increase in temperature.
A temperature increase can be caused by:
You can avoid the destruction of the cell by too much pressure in the following ways:
Please note that high pressure may destroy some other kinds of cells as well. This occurs if the liquid contained is subjected to extreme changes in temperature. For
example, cells for anaerobic measurements may be affected. On the one hand it is possible to cool an empty cell down to just few Kelvin without destroying it, but the same cell, even if it is not sealed will burst, if filled with water and brought to a temperture a few degrees below the freezing point. The reason for this is the fact that water does not only expand upwards when it freezes, but in all directions equally which can cause the cell to burst.