Early 20th-century engraving of a gravity cell. Note the distinctive crowfoot shape of the zinc anode.

The Daniell cell (var. sp. Daniel cell), also called the gravity cell or crowfoot cell was invented in 1836 by John Frederic Daniell, who was a British chemist and meteorologist. The Daniell cell was a great improvement over and is somewhat safer than the voltaic cell used in the early days of battery development. The Daniel cell's theoretical voltage is 1.1 volts and the chemical reaction is: Image File history File links Download high-resolution version (553x700, 66 KB) Engraving of a gravity cell from the Cyclopedia of Telegraphy and Telephony, published in 1919. ... Image File history File links Download high-resolution version (553x700, 66 KB) Engraving of a gravity cell from the Cyclopedia of Telegraphy and Telephony, published in 1919. ... Year 1836 (MDCCCXXXVI) was a leap year starting on Friday (link will display the full calendar) of the Gregorian Calendar (or a leap year starting on Wednesday of the 12-day slower Julian calendar). ... John Frederic Daniell (March 12, 1790 - March 13, 1845) was an English chemist and physicist. ... A chemist pours from a round-bottom flask. ... Meteorology is the scientific study of the atmosphere that focuses on weather processes and forecasting. ... Voltaic cell can connote: Galvanic cell Voltaic pile see also: battery (electricity), fuel cell This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Four double-A (AA) rechargeable batteries In science and technology, a battery is a device that stores chemical energy and makes it available in an electrical form. ... International safety symbol Caution, risk of electric shock (ISO 3864), colloquially known as high voltage symbol. ... Vapours of hydrogen chloride in a beaker and ammonia in a test tube meet to form a cloud of a new substance, ammonium chloride A chemical reaction is a process that results in the interconversion of chemical substances. ...

Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)

The Daniell cell proper consists of a central zinc anode dipping into a porous earthenware pot containing zinc sulphate solution. The porous pot is, in turn, immersed in a solution of copper sulphate contained in a copper can, which acts as the cell's cathode. The use of a porous barrier prevents the copper ions in the copper sulphate solution from reaching the zinc anode and undergoing reduction. This would bring the battery to equilibrium without it driving a current. In other words, it would make the battery dead. General Name, Symbol, Number zinc, Zn, 30 Chemical series transition metals Group, Period, Block 12, 4, d Appearance bluish pale gray Atomic mass 65. ... General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic pinkish red Standard atomic weight 63. ... General Name, Symbol, Number zinc, Zn, 30 Chemical series transition metals Group, Period, Block 12, 4, d Appearance bluish pale gray Atomic mass 65. ... Diagram of a zinc anode in a galvanic cell. ... Zinc sulfate (ZnSO4) is a clear, crystalline, water soluble chemical compound. ... Copper (II) sulfate (CuSO4) is the most common copper salt, made by the action of sulfuric acid on the base copper oxide. ... General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic pinkish red Standard atomic weight 63. ... Diagram of a copper cathode in a Daniells cell. ... Illustration of a redox reaction Redox (shorthand for oxidation/reduction reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. ...

In the 1860s, a Frenchman named Callaud invented a variant of the Daniell cell which dispensed with the porous barrier. Instead, a layer of zinc sulphate sat on top of a layer of copper sulphate, the two kept separate by their differing densities. The zinc anode was suspended in the top layer whilst the copper cathode sat in the bottom layer. A layer of oil was often added on top to prevent evaporation. This variant was known as the gravity cell, and sometimes the crowfoot cell due to the distinctive shape of the electrodes. This arrangement was less costly for large multicell batteries but could not be moved and was vulnerable to loss of integrity if too much electric current was drawn, which would cause the layers to mix. Electric current is by definition the flow of electric charge. ...

External links

• Daniel Cell Experiment