36 DISINFECTANT 



celery, cabbage, colowort. Lime was found to prevent, but not to remove putrefac- 

 tion. We are inclined at present very much to qualify some of these observations. 

 Animal fluids, ho observes, will remain for a long time without putridity if kept 

 from the air. lie says that astringent mineral acids and ardent spirits 'not only 

 absorb the matter from the putrescont substances, but likewise crisp up its fibres, and 

 thereby render it so hard and durable that no change of combination will take place 

 for many years.' He adds also molasses to the antiseptics. In 1767 tho Academy of 

 Dijon gave a prize for the use of nitrate of potash in ventilation, driving off the oxygen 

 by heat. This may have given tho first idea to Carmichael Smyth using the nitrous 

 fumes. Guytpn-Morveau came later with a volume of valuable experiments on acids 

 chiefly muriatic. 



An antiseptic preserves from putrefaction, but does not necessarily remove the odour 

 caused by that which has previously putrefied. Many of the substances described as 

 disinfectants here might equally be called antiseptics. When they remove the putrid 

 matter, they are disinfectants ; when they prevent decomposition, they are antiseptics. 

 But when the smell is removed by a substance which is known to destroy putrefactive 

 decomposition, and to preserve organic matter entire, then we have the most thorough 

 disinfection ; then we know that the removal of the smell is merely an indication of 

 the removal of the evil. 



Disinfectants are of various kinds. Nature seems to use soil as one of the most 

 active. All the dejecta of the animals on the surface of the earth fall on the soil, and 

 are rapidly made perfectly innoxious. Absorption distinguishes porous bodies, and 

 the soil has peculiar facilities for the purpose. But if saturated, it could disinfect 

 no longer. This is not allowed to occur; the soil absorbs air also, and oxidises the 

 organic matter which it has received into its pores, and the offensive matter is 

 cither converted into food for plants and absorbed by them, or is made an innocent 

 ingredient of the air, or, if the weather be moist, of the water. The air is, therefore, 

 in^conj unction with the soil, one of the greatest disinfectants, but it acts also quite alone 

 and independent of the soil. Its power of oxidising must be very great. The amount 

 of organic effluvium sent into large towns is remarkable, and yet it seldom accumulates 

 so as to be strongly perceptible to the senses. The air begins to oxidise it almost as 

 rapidly as it rises ; this is hastened apparently by the peculiar agent in the air, ozone, 

 which has a greater capacity of oxidation than the common air ; when this is exhausted, 

 it is highly probable that the oxidisation will be much slower, and this exhaustion 

 does take place in a very short time in our large and smoky towns. So rapid is the 

 oxidation, that the wind, even blowing at the rate of fifteen to twenty miles an hour, 

 is entirely deprived of its ozone by passing over less than a mile of Manchester. In 

 London this does not take place so rapidly, at least near the Thames. But when the 

 ozone is removed, it is probable that the rate of increase of the organic matter will 

 be much greater. We may by this means, then, readily gauge the condition of a town 

 up to a certain point by the removal of the ozone : but it requires another agent to 

 gauge it afterwards or thoroughly. 



It is in connection with each other that the air and tho soil best disinfect. When 

 manure is thrown upon land without mixing with the soil, it may require a very long 

 period to obtain thorough disinfection, but when tho atmosphere is moist, or rain falls, 

 then the air is rapidly transferred into every portion of the porous earth, and the 

 organic matter becomes rapidly oxidised. To prevent a smell of manure, and with it 

 also the loss of ammonia, it is then needful that as soon as possible tho manure should 

 be mixed with the soil. The same power of oxidation is common to all porous bodies, to 

 charcoal, and especially, as Dr. Stenhouse has shown, to platinised charcoal. Disin- 

 fection by the use of porous bodies is at first a process of preservation, but soon it 

 may change to that of slow destruction. It has been shown by tho last-mentioned 

 chemist that charcoal produces an oxidation in which all the escaping gases are so 

 thoroughly oxidised, that none of them have any smell or any offensive property. 

 But being so, the body disinfected must necessarily decay, and in reality the \ 

 of decay is remarkably increased. All such bodies must therefore be avoided uln-n 

 manures aro to be disinfected, and when they are not to bo put on tho land imme- 

 diately. Stenhouso has employed charcoal for disinfecting tho air. The air is passed 

 through tho charcoal either on a largo scale for a hospital or on a small scale as a 

 respirator for the mouth. Care must bo taken, however, to keep tho charcoal dry : 

 wet charcoal is not capable of absorbing air until that air is dissolved in tho water. 

 This absorption takes places less rapidly in water. Wot charcoal is thcr 

 filter for fluids chiefly, and dry charcoal for vapours. Its destructive action on 

 manures will, however, always prevent charcoal from being much used as a disinft ri.mt 

 for such purposes, or, indeed, any other substance which acts principally by its 

 porosity or by oxidation. This tho soil does only partially, as it has another power, 

 viz, that of retaining organic substances fit to be tho food of plants. Although air 



