Reagent tablets offer the highest level of assurance that always the exact amount of reagent needed will be used. Most marketed tablet types, such as DPD for determining Chlorine in water, are regulated by strict international standards aimed at guaranteeing that all tablets with that designation (e.g. DPD 1) can also be used in all designated measurement devices made by any manufacturer. Water-i.d.® devices and reagents can therefore be combined with other manufacturers’ reagents, and this is also true the other way around. One of the questions discussed often is the difference between RAPID and Photometer tablets. Basically, both detect the same content but are different in one important point: RAPID tablets contain a material that “bursts” the tablet, e.g. chemical pulp that expands upon contact with water. This “burst material” would, however, disrupt the light ray of the photometer (suspended particles) which is why RAPID tablets should never be used with electronic devices such as photometers.