A volt meter should be used to determine the condition of the battery, and should be used frequently. An ammeter should never be used on a storage battery, as it is of very low resistance, and would probably cause a rush of current that would destroy both the battery and the instrument. Never short circuit a storage battery, even for an instant, as excessive current will cause the plates to buckle, or will loosen the active material on the plates. The plates are immersed in the electrolyte, which should cover the entire plate or active surface. If the solution does not cover the plate, the capacity of the cell will be reduced. Plates that are partially covered with solution deteriorate rapidly from “sulphating.” This is caused by the air and acid acting on the damp inactive portion of the plate. Usually the electrolyte consists of a dilute solution of sulphuric acid and water, but in some ignition cells the solution is “solidified” by some substance to about the consistency of table jelly. The object of this thickened solution is to prevent the solution from slopping and leaking when the battery is being transported. The solution used in a storage battery is exceedingly corrosive in its action, and if spilled on metal or wood will destroy it immediately. Care should be taken in handling the electrolyte. A cell should never be discharged below 1.7 volts for below this point, the plates are likely sulphate. When the solution is replaced by fresh, or water is added for the purpose of restoring the electrolyte to its original level, use only distilled water, free from metallic salts and suspended matter. Many people “test” their cells by snapping a wire across the terminals to “see if there is a good spark.” Nothing could be more injurious to the battery, and as this test indicates nothing, the practice should be discontinued. Make all your tests either with a hydrometer or a voltmeter, the latter is preferable in the average case. The electrolyte is a solution containing approximately 10% of chemically pure sulphuric acid and 90% of distilled water. The specific gravity of the fluid should be from 1,210 to 1,212 in all cases. A standard battery hydrometer should be used by all storage battery users to ascertain the exact density of the solution as the specific gravity is a direct index to the condition of the cell. A gasoline hydrometer is useless for a storage battery. When mixing the electrolyte it should be placed in a glass or porcelain jar, and the process should never be performed in the battery jar in the presence of the plates. The solution is very active chemically and should not be brought into contact with metallic or organic substances because of the danger of contaminating the fluid. The acid should always be poured into the water in a thin stream while the mixture is being stirred with a glass or porcelain rod. Pouring the water into the acid is likely to produce an explosion and should therefore be carefully avoided.