Shelf life mercury zinc

However, if the initial ammonium chloride concentration is depleted, the reaction, as indicated above, becomes more complex and formation of hydroxochloro complexes plays an increasingly important role. The zinc alloy sheet used for the anode manufactme contains small quantities of lead and cadmium, and various corrosion inhibitors, such as a soluble mercury salt, are added to improve shelf life. 

Cadmium/Mercuric Oxide Battery. The substitution of cadmium for the zinc anode (the cadmium/mercuric oxide cell) results in a lower-voltage but very stable system, with a shelf life of up to 10 years as well as performance at high and low temperatures. Because of the lower voltage, the watthour capacity of this battery is about 60% of the zinc/mercuric oxide battery capacity. Again, because of the hazardous characteristics of mercury and cadmium, the use of this battery is limited. 

SAFT supply this type of battery. The particular advantages claim for lithium-copper oxide batteries are long operating life, long shelf life (up to 10 years projected) and high operating temperature (tested between — 20 and - -50°C). Volumetric capacity (Ah/dm ) is 750 compared with 300 for alkaline manganese dioxide, 400 for mercury-zinc and 500 for lithium—sulphur... 

In the common dry cell the electrolyte is a concentrated ammonium chloride solution containing some zinc chloride and a small amount of mercury(II) chloride. The latter is reduced to mercury at the zinc surface, which reduces the corrosion (q.v.) rate and adds to the shelf life of the cell. The usual form of the cell is a zinc container, acting as anode, next to which is a layer of the electrolyte mixture made into a gelled paste by addition of starch or flour. Inside this is the Mn02-C mixture surrounding a central carbon rod the latter is fitted with a metal cap to act as positive terminal, and the cell is sealed with a bitumen layer. 

---