Service chemistry : being a short manual of chemistry and metallurgy and their application in the naval and military services / by Vivian Byam Lewes and J.S.S. Brame.

  • Vivian Byam Lewes
Date:
1913
Catalogue details

Licence: In copyright

Credit: Service chemistry : being a short manual of chemistry and metallurgy and their application in the naval and military services / by Vivian Byam Lewes and J.S.S. Brame. Source: Wellcome Collection.

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    given by the battery ; and such a source of electricity is called a gas battery. In the same way, if a strong current be passed through slightly acidulated water, between two lead plates, one lead plate becomes oxidised on the surface and coated with a brown powder known as peroxide of lead or lead dioxide (PbOg); if now the battery be removed and the two electrodes be con- nected by a wire, a current in the reverse direction is produced and one-half the oxygen from the lead dioxide appears on the other lead plate, coating it with htharge or lead monoxide (PbO), so that both plates are now coated with lead monoxide and are alike, and the current ceases. In practice, the plates are made of cast lead in the form of grids, the holes being about |-inch square, and one plate has the holes filled with a paste of lead monoxide (PbO) and dilute sulphuric acid, whilst the other has the holes filled with red lead (Pbg04) ; these plates are then placed in a vessel of dilute sulphuric acid and connected to a dynamo or other generator of electricity, and a current passed from the red lead (Pb304) plate to the lead monoxide (PbO) plate. The lead monoxide is reduced to spongy metallic lead, whilst the red lead is oxidised to lead peroxide. The plates so prepared are arranged alternately in a vessel and are kept apart by india-rubber plugs, the vessel being filled with dilute sulphuric acid (sp. grav. IT5), and on coimecting them a current is set up. Before dischargmg we find lead dioxide (PbO2) at one plate and metalhc lead at the other, both in presence of sulphuric acid. After action we have lead sulphate (PbS04) and water (HgO) formed—both plates having become coated with lead monoxide (PbO), which has then been converted by the sulphuric acid into lead sulphate (PbS04). The action is a reversible one, and may be expressed by the equation— ]>oad Lead peroxide Sulpliuric acid Load sulphate Water Pb + PbOo + 2H0SO4 ^ 2PbS04 H- 2H2O Edison Nickel Cell.—The })Ositive plate of this cell consists of a steel frame carrying a number of perforated steel tubes originally charged with nickel liydroxide (NiOH)2, and flaked metallio nickel, the latter to ensure better contact. The negative plate is also of steel, and has perforated sides, the perforations being filled with iron oxide Pe(HO)3. The electrolyte is a 21 per cent, solution of caustic potash, containing a little litliia.
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