The solutions of these salts in water, are sprinkled occasionally through the apartments which are to be purified. When these solutions are sprinkled about, and exposed to the action of the air, the chlorine escapes in its gaseous form and mingles with the atmosphere, while the lime and soda, which are now uncombined, attract and unite with any carbonic acid which may have arisen from the patient, his clothes, or excretions. The solution of chloride or chloruret of lime, answers sufficiently well, but as it is to be obtained in all drug shops, it is unnecessary to add here a formula for its preparation. FORMULA FOR THE PREPARATION OF CHLORINE GAS. Take three parts of common salt, one of black oxide of manganese, and three of strong oil of vitriol. Mix the salt and the oxide together in a stoppered retort, pour in the oil of vitriol and apply a gentle heat. The gas is immediately evolved, and rapidly diffuses itself throughout the atmosphere. Muriatic acid gas, a combination of chlorine and hydrogen gases, though considered as inferior to chlorine as a fumigation, is frequently employed for the purpose of decomposing effluvia, as the materials for its preparation are almost ever at hand. FORMULA FOR OBTAINING MURIATIC ACID GAS. Put a handful of common salt previously made very hot into a saucer, and pour over it an ounce of strong oil of vitriol. The gas is immediately extricated. It has been already said that the fumigations just noticed are on many occasions highly useful, and their employment is much recommended in all situations where the atmosphere is liable to be contaminated by effluvia from sick persons or from dead bodies; but it is not therefore to be understood that, because the use of these agents has been advocated, it is for the purpose of destroying atmospheric contagion, of decomposing the specific animal poisons which have been supposed to be present, and dissolved in the atmosphere, which is the object, or one of the objects, held in view by the generality of those who advise the use of fumigations. These fumigations have been recommended with the view of correcting what has been treated of as vitiated air, which is distinct from, but which has long been erroneously regarded as, Atmospheric Contagion. On some occasions, great fires of wood, coal, pitch, gunpowder, and the like, have been recommended for the purpose of destroying contagion and purifying the atmosphere. During the prevalence of the plague in London, great fires were kindled in the streets, and, according to some historians, with considerable benefit. Such great fires produce great agitation of the atmosphere, and it is possible that in this way they may prove useful in improving the condition of that fluid, particularly when, as happened occasionally during the visitations of plague in London, the weather is sultry and close, and when the atmosphere is confined and little agitated, and allowed almost to stagnate.