Germicides are the chemicals which prevent growth of germs (microorganisms). Germicides are classified as antiseptic and disinfectant. Both kill microorganisms but the difference lies in the way you can use them.
Antiseptics kill microorganisms and are safe to be used on living beings (tissues). Antiseptics are used on wounds, cuts or skin abrasions. These are used to dress wounds, etc. For example, iodoform (CHI3), tincture of iodine, ethyl alcohol, a 0.2 percent aqueous solution of phenol and boric acid (H3BO3) are common antiseptics.
Iodine is a powerful antiseptic. It is used as tincture of iodine. Tincture of iodine is 2 to 3 percent solution of iodine dissolved in ethyl alcohol. Iodoform is a yellow coloured solid, which is used as an antiseptic.
Disinfectants kill germs (microorganisms) but are used on non-living substances like surgical instruments, floors, bathrooms, lavatories, etc. Disinfectants are harsh and are not safe to be used on living beings as disinfectants can damage living tissues.
Chlorine is a powerful oxidizing agent. It is used for disinfecting water. A concentration of 0.2 to 0.4 ppm (parts per million) is enough to kill microorganisms present in water.
Low concentration of sulphur dioxide is used to kill microorganisms in jams, jellies and squashes. Thus it acts as a food preservative. Sulphur dioxide is used for fumigation in rooms, operation theaters, etc. to sterilize them. Bleaching powder (CaOCl2), chlorine (Cl2), mercuric chloride (HgCl2), sodium hypochlorite (NaClO), sulphur dioxide (SO2) etc. are other examples of disinfectants.
It is interesting to note that 0.2 percent aqueous solution of phenol is used as antiseptic by making. It is safe to be used on living tissues in low concentrations (less than 0.2 percent). If concentration of phenol is high then it can damage tissues. Therefore, at higher concentration (1 percent or more) phenol is used as disinfectant.