Skip to main content

The National MagLab is funded by the National Science Foundation and the State of Florida.

Magnet Academy logo
search icon

Daniell Cell

English chemist John Frederick Daniell came up with a twist on the simple voltaic cell.

In 1836, Daniell's modification of the simple electrical cell resulted in a longer-lasting source of power. It is known as the Daniell cell.

Daniell’s setup isolated the copper and zinc ions from each other, preventing polarization from interrupting the flow of electricity. At the same time, it allowed ions in the electrolyte to move between the two metals, necessary to complete the electrical circuit.

Let’s take a look at how this works.

Instructions

  1. See the container lined with copper forming the outer portion of the device. It’s filled with copper sulfate, an electrolyte that reacts chemically with the solid copper. This is the cathode of the cell.
  2. Note the second slightly porous container inserted into the first. It contains a zinc rod in an electrolyte of zinc sulfate. This is the anode.
  3. The zinc oxidizes in the zinc sulfate, producing leftover electrons, denoted as tiny yellow particles. When the two metals are connected by an external circuit, the copper attracts the electrons left over in the zinc.
  4. The electrons the copper receives from the zinc through the circuit combine with the positively charged copper ions. These are depicted as dark copper colored particles. This forms deposits of solid copper on the metal, depicted by the lighter copper-colored particles.
  5. Notice the sulfate ions shown as blue and yellow molecules. These also play an important role in maintaining this circuit. For every pair of electrons the copper pulls from the zinc, a sulfate ion bearing two negative charges passes from the copper side through the porous container to the zinc side to compensate. This allows the electron flow through the circuit to continue.
  6. Back on the zinc side, the zinc breaks up into positive ions, the light gray particles, that combine with the incoming sulfates, releasing more electrons to the system to keep the circuit going.

This cell was designed to be used in a series of identical cells to create a relatively long-lasting battery, and as such was an improvement over the voltaic pile, the world's first battery invented some three decades earlier.