Because of their effectiveness, relative economy and ease of production, poison gas and other chemical weapons have been called the poor nation's atomic bomb. Here is a list of some gases in the chemical arsenal, drawn from "Chemical Warfare," a book by Edward M. Spiers, published by University of Illinois Press:

- CHLORINE: Chlorine irritates the nose, throat and lungs and causes coughing, smarting of the eyes, nausea and vomiting. A 0.1 percent concentration causes death within a few minutes.

- PHOSGENE: Phosgene is 10 times more toxic than chlorine, but severe symptoms and death may not occur for several hours after exposure. Phosgene damages the air sacs of the lungs, causing a deadly accumulation of fluid in the lungs. Victims less severely affected may cough bloody sputum for months. Phosgene caused 80 percent of the gas fatalities in World War I. A 0.02-0.05 percent concentration kills in minutes.

- MUSTARD: Mustard gas blisters and burns the skin or lungs on contact. It also attacks the eyes, causing inflammation of the inner surface of the eyelids, and causes hoarse coughing and bleeding from the nose. Symptoms are delayed for 2-4 hours unless one is directly exposed to the liquid. A concentration of one-tenth of a milligram per liter for 10 minutes is fatal.

- HYDROCYANIC ACID: Hydrocyanic acid affects the nervous system. Also known as prussic acid, it can be absorbed through the skin and acts rapidly on its victims. Symptoms progress through giddiness, headache and unconsciousness to convulsions and paralysis of the brain's respiratory center. A concentration of 2.5 milligrams per liter is fatal.

- LEWISITE: Lewisite is absorbed through the skin and lungs, acting as both a blistering-burning agent and a poison because it contains arsenic. Lewisite has effects similar to those of mustard gas, but the symptoms are more severe and burns appear sooner. A concentration of one-tenth of a milligram for 10 minutes is fatal.> - ADAMSITE: At low concentrations, adamsite irritates the mucous membranes of the nose and throat. The lower respiratory tract is affected by higher concentrations. A concentration of 3 milligrams per liter for 10 minutes is fatal.

- SNEEZE AND NAUSEA GAS: This gas causes sneezing, choking, headache, chest pains and vomiting. Twitching and an unsteady gait result from higher concentrations. A concentration of 3 milligrams per liter for 10 minutes is fatal.