The carbon electrode is in the form of a corrugated hollow cylinder which engages by means of an internal screw thread a corresponding screw thread on the outer side of the carbon cover.  Within this cylinder is contained a mixture of broken carbon and peroxide of manganese.  The zinc electrode is in the form of a hollow cylinder almost surrounding the carbon electrode and separated therefrom by means of heavy rubber bands stretched around the carbon.  The rod, forming the terminal of the zinc, passes through a porcelain bushing on the cover plate to obviate short circuits.  This type of cell has an electromotive force of about 1.55 volts and recuperates very quickly after severe use.  It also has considerably lower internal resistance than the type of LeClanche cell employing a porous cup, and, therefore, is capable of generating a considerably larger current.

Cells of this general type have assumed a variety of forms.  In some the carbon electrode, together with the broken carbon and peroxide of manganese, were packed into a canvas bag which was suspended in the electrolyte and usually surrounded by the zinc electrode.  In other forms the carbon electrode has moulded with it the manganese depolarizer.

In order to prevent the salts within the cell from creeping over the edge of the containing glass jar and also over the upper portion of the carbon electrode, it is common practice to immerse the upper end of the carbon element and also the upper edge of the glass jar in hot paraffin.

In setting up the LeClanche cell, place not more than four ounces of white sal ammoniac in the jar, fill the jar one-third full of water, and stir until the sal ammoniac is all dissolved.  Then put the carbon and zinc elements in place.  A little water poured in the vent hole of the porous jar or carbon cylinder will tend to hasten the action.

An excess of sal ammoniac should not be used, as a saturated solution tends to deposit crystals on the zinc; on the other hand, the solution should not be allowed to become too weak, as in that case the chloride of zinc will form on the zinc.  Both of these causes materially increase the resistance of the cell.

A great advantage of the LeClanche cell is that when not in use there is but little material waste.  It contains no highly corrosive chemicals.  Such cells require little attention, and the addition of water now and then to replace the loss due to evaporation is about all that is required until the elements become exhausted.  They give a relatively high electromotive force and have a moderately low internal resistance, so that they are capable of giving rather large currents for short intervals of time.  If properly made, they recuperate quickly after polarization due to heavy use.

Dry Cell.  All the forms of cells so far considered may be quite properly termed wet cells because of the fact that a free liquid electrolyte is used.  This term is employed in contradistinction to the later developed cell, commonly termed the dry cell.  This term “dry cell” is in some respects a misnomer, since it is not dry and if it were dry it would not work.  It is essential to the operation of these cells that they shall be moist within, and when such moisture is dissipated the cell is no longer usable, as there is no further useful chemical action.