This is a less numerous division of disinfectants than the oxidizers. it nevertheless contains at least one article which, in its efficiency and the extent of its application, is scarcely inferior to any one of the whole class. The products of organic decomposition which arc so effectually destroyed by combination with oxygen, are scarcely less effectually destroyed or prevented by the abstraction of oxygen from them, or its denial to them. in the changes which take place in decomposition, oxygen is an essential agent. The first step of nature in organic decomposition is to produce, by the agency of oxygen, offensive compounds; but by a continuance of the process these noxious gases are in their turn still further oxidized, and in the end completely destroyed; nature performing slowly what is rapidly effected by the oxidizing agents. if, therefore, oxygen is denied, the offensive matters cannot be generated; and those already produced are destroyed by the loss of the little they already contain. Of the deoxidizing agents very few are actually employed; the whole list including only sulphurous acid, the sulphites, nitric oxide, and perhaps ammonia.

Sulphurous Acid and the Sulphites are among the most efficient of the disinfectants. So far as they belong to the present division, they are chemical agents, operating by the affinity of the acid for oxygen. Certain compounds of oxygen, in which the affinity of the base for that element is not satisfied, have a strong disposition to combine with more, in order to pass to a higher state of oxidation. This is the case both with the acid and basic compounds of oxygen, and both carry the tendency into their combinations with each other. Thus, sulphurous acid seeks oxygen eagerly in order that it may pass into the sulphuric, and the protoxide of iron has a similar eagerness in order to become peroxide; and the acid and base, united as sulphite of protoxide of iron, seize oxygen with avidity whereby this may be converted into sulphate of the peroxide. Hence the efficiency of the sulphurous acid and the sulphates as deoxidizing disinfectants. But as they operate with still greater efficiency to the same result as parasiticides, I shall consider them especially in that class of remedies, in the subdivision of antizymotics, to which the reader is referred.

Nitric Oxide, or deutoxide of nitrogen (N02), is a disinfectant formerly in great repute. it is a gaseous body, consisting of one eq. of nitrogen and two eqs. of oxygen; but so great is its affinity for oxygen that it cannot exist for an instant in contact with the air without passing into a higher state of oxidation, giving rise to red fumes, of which the greater portion consists of hyponitric acid (No4), and which are so striking an attendant of the action of nitric acid on the metals. These nitrous fumes were formerly much employed in cleansing the foul air of ships, privies, hospitals, etc., but, being less efficient than chlorine, have been almost if not entirely superseded by that disinfectant. Nitric oxide may be prepared at any time by adding nitric acid to copper, or to any other metal for which it has a strong affinity. The metal takes three eqs. of oxygen from a portion of the acid (N05), liberating the peroxide of nitrogen (N02), which then combines with the oxygen of the air to form nitrous fumes. But these, having a strong tendency to become nitric acid (N05), act as a disinfectant, probably by abstracting oxygen from the impurities of the atmosphere. it is possible that the efficacy of nitric acid and the nitrates, as disinfecting agents, may be in part owing to the reaction, in the nascent state, between the odorous products and the lower oxide or acid which the nitric yields by its own deoxidation.

Sulphate of Protoxide of iron, of which I have already spoken as an oxidizing disinfectant, through the decomposition of its acid, probably owes part of its efficiency to the deoxidizing power of the protoxide of iron, which, whether separate or combined, seizes upon oxygen where-ever it presents itself in order to become peroxide.

Ammonia acts as a disinfectant, not by taking oxygen from the offensive products, but by absolutely preventing, simply by its presence, the combination of oxygen with these bodies. it perhaps might be considered as antiseptic rather than strictly disinfectant. This use of ammonia we owe to Dr. Richardson, of London, who has so greatly distinguished himself by his experimental researches in various directions. So strong is this anti-oxidizing power of ammonia that even potassium will not combine with oxygen in its presence. Dr. Richardson recommends it highly for the prevention of animal putrefaction. He has found that blood, milk, and solid tissue may be kept perfectly sweet indefinitely, if immersed in an atmosphere of ammonia, even in the presence of oxygen. it may, he thinks, be used with great benefit for the preservation of specimens of morbid structure, and of portions of the body for forensic purposes, or for examination by the knife or the microscope. He proceeds as follows; first taking care that no other preservative agent shall have been previously employed. For liquids, as blood or milk, he simply adds the officinal stronger solution of ammonia, in the proportion of twenty minims to two fluidounces of the liquid. For solid tissues, he introduces the portion to be kept into a broad-mouthed, stoppered glass jar, or beneath a bell-glass, in which a piece of felt or patent lint has been placed, charged with from ten minims to a fluidrachm of the ammoniacal solution, and then closes the vessel carefully, air-tight, using preferably for this purpose a luting either of soap, or of this mixed with red oxide of lead. (Med. Times and Gaz., May, 1862, p. 492.)