Devices for the essential control of pH

The control of pH in the form of the Deltatrode 120, which was being shown in Tanning Tech, is a joint venture between Olcina and Swystem Logic and is the first step in precision process control. By eliminating the conventional metal ions in the reference half-cell, pH can be measured without fear of electrode poisoning by sulfides, chrome-complexes, vegetable tans and syntans. The Deltatrode is complemented by the Knick Protos dual high impedence amplifier/ transmitter which is required for this 'differential pH electrode'. A further element is the Retractomatic, a tool which ensures absolute reproducibility in contaminated tanning liquors. John Crowther, Swystem Logic, who was present on the Olcina stand to offer advice and demonstrations, believes that resolving the problems of efficiency and waste in leather-making goes beyond mere automation. It depends on real control of the process, beginning with recording real, accurate values of pH and other essential control parameters. It all begins with pH because, as Crowther asserts, this is the most important and least well managed aspect of leather manufacture. The benefits of taking full advantage of modern, proven technology are waste avoidance (thus reducing costs) and achieving leather quality consistency between successive deliveries to the client. Firstly, there is the breakthrough 'differential electrode' - Deltatrode from Hamilton Bonaduz - which is resistant to poisoning by the usual tannery chemicals. This allows the electrode to be continually immersed, yet consistently provide accurate pH readings, a feature which, as tannery technicians are only too aware, has eluded the leather industry since pH meters were first invented. Deltatrode needs low maintenance, infrequent calibration, and is reliable up to 60°C. Associated with this electrode is an 'armature' device, Retractomatic, which allows the electrode to be quickly and easily retracted from the process liquor in the lab-box or recirculation pipeline. When retracted, the electrode enters a sealed compartment where it may be rinsed, then calibrated with standard buffers. A 24V motorised version is also available, which permits automatic rinsing and calibration at intervals as frequently as set by the technician.