decomposition, and water of peat-bogs gives out no injurious gases, for the peat does not putrefy.

as rapidly as it destroys. These stores of saltpetre from India and South America are used for oxidizing. They are concentrated air, which burns charcoal so rapidly as to make an explosion, and which purifies ex

We have not been able to use this power hitherto for household disinfection in bad cases, it is almost too powerful, but we use it as an antiseptic for preserving meat, to which saltpetre is added; it has also a pow. erful action, especially free, as nitric acid, in restraining putrefaction, although the mode of using it is not yet made quite clear.

So powerful is this action of oxygen that even when all the organic matter is decomposed, this remarkable gas continues to ac-actly as air purifies. cumulate when it can find entrance, and heaps itself up around certain bodies, forming nitric acid—a reservoir of air for the use of any more vegetable matter which may arrive. It is thus that near the most impure places, if the water passing through them is detained long on the road, the organic matter is removed thoroughly, and the nitric acid formed is sufficient to give it a strong taste. It is nature making violent exertion to bring a supply of oxygen where it is most wanted. Strange to say, this accumulation is made by nitrogen, the very substance which is found characteristic of bodies capable of putrefaction. This nitric acid is united with lime, magnesia, or potash, and with the latter makes saltpetre.

In times gone by, and even later than Shakspeare's, our floors were the earth only, as in many cottages now, and we used the broom or brush little, and threw the garbage down, allowing it to lie and rot and become so vile that we invented the device of covering it over with straw, so that it might be trodden down, as the cattle make the manure in the straw-yards. The earth of the floor was overweighed with putrid matter, and much of it came into the air of the room, but the formation of nitre or saltpetre began, and oxygen accumulated rapidly, and rendered even these houses habitable in a way. The Government soon found out this growth of saltpetre, and sent Petremen to obtain it by force. They entered houses without pity, and seemed to increase the discomfort of a household to the utmost, that they might be bribed to leave. It is not for us here to describe the tyranny of these wretches, but their doings illustrate, much more even than the more distant miseries of war did, Shakspeare's words, 'villanous saltpetre.' 'The harmless earth,' out of which it was dug, is a metonymy, and may mean rather the earth in the house of a harmless family, where perhaps some tender life was lying in danger, whilst these men insisted on removing the bed, and rendering the whole apartment wretched.

It was fortunate when the search for saltpetre, like war itself, went abroad. Now we find that great collections of oxygen in this way have been made in old times, and are lying ready for our use, just as collections of coal and firewood have been made for a population too large to grow enough for itself, or too wanting in foresight to plant

There are, however, other bodies which condense oxygen, and one which we get chiefly from Norway brings us chromic acid and chromate of potash, remarkable agents in antisepting. We must coin the word to antisept; we have none that can take its place.

But even chromic acid has not become familiar, and we must look to other oxidizers. We have chloric acid, a body with still more oxygen, and most powerful, and its compound, chlorate of potash, which may also be used. All these bodies give out oxygen, and are therefore oxidizers, antiseptics, purifiers, and disinfectants. But they are not enough, because practice has not taught us the best modes of applying the peculiar characteristics of each. Manganese condenses oxygen, forming permanganate of potash, a substance beautiful in colour and innocent in character, whilst it oxidizes powerfully all the foulest bodies, and removes the most putrid odours as if by magic. We have to thank Mr. Condy for teaching us its use. It is certainly an elegant disinfectant, a name which it bears in opposition to antiseptic, which it is not, as it does not preserve. This permanganate, sometimes called chameleon, may be put into the foulest water or the most repelling mixtures, and the sense of smell will cease to be offended, whilst we may be sure also that the injurious bodies which do not smell will be equally oxidized. It leaves potash and oxide of manganese. It would be well if we could get the permanganic acid without the potash, and when it had done its work it would quietly fall to the bottom of the vessel, and if we were using it to purify drinking-water, we should have only a little brown oxide, which would do no harm, or if it had an unpleasant appearance, we might let it sink and leave the liquid above perfectly pure. We have certainly one solution which has all these advantages, that is, pure oxide of water, or peroxide of hydrogen. It looks like water; if we pour it on the filthiest substance the smell of putrefaction ceases, and in many

cases a sweet odour or fragrant perfume, [ to take, and so act as carriers, and these nicreated in an instant, arises in its place. trates and chromates require attention. But The peroxide has given up its oxygen and the world seeks exact knowledge; we shall pure water only remains, no remnant to endeavour to distinguish here some of the which we can object. Is there anything be- known from the uncertain. yond this? Scarcely, although it does not seem applicable to all waters. It is dear, unfortunately, but some day it may be cheaper. There are places where it can be had cheaply, but in small quantities. Here also work is needful, and although we know these remarkable qualities we do not know details, and cannot yet tell how far it can be generally used; every substance has a character as complicated as the relations to all other substances and conditions of substances can make it.

Although knowing the wonderful position oxygen takes as purifier in nature, we use it very little directly; we leave its work to nature. Permanganate is the form in which we can best use it, and it is scarcely fitted for universal use from its price. We want a few more oxidizers. There are numerous bodies ready to oxidize, manganese and iron freshly precipitated, ready to give and then of Manchester, vol. xii.

pound of hydrogen and carbon, is one of these unburnt gases given out.

hold a very high place, but there is a diffiAs a fumigating disinfectant sulphur must

culty in most cases of keeping up the sup ply. It burns and goes out readily. We desire to keep it constantly burning. This cannot be well done in small quantities; it would for small spaces be best to use a sulphite of soda or lime, and add a little weak muriatic acid to it; in this way the supply for fumigation might be kept up.

The dome he purges, now the flame aspires.' The shepherds purified their sheep with it as well as bleached their wool, and in Ovid's Fasti (Book iv., lines 739, 740), 'Let blue smoke arise from the burning sulphur, and let the sheep bleat when touched by the When the gas combines with any body, smoking sulphur.' The Italians may it forms a sulphite. Sulphite of soda, lime, perhaps have it by tradition as a mode of etc., are disinfectants. They act by removpurifying their vines and their wine-casks, ing smells, not all, most decidedly, but for which, indeed, it is used over all the some. The most putrid blood will become wine-growing shores of the Mediterranean, comparatively innocent when sulphites are to such an extent, that a new Etna neigh- added, but a smell remains, a concentration bourhood would be a commercial advantage, of that which we find in a slaughter-house. since the Greeks do not use as of old the The worst part, perhaps all the dangerous volcanic island of Melos for sulphur. Brim- part, is removed. It goes on acting, and stone was used for skin diseases and in gives up all its oxygen, until at last sulpoultices of old, and the smell of it is phuretted hydrogen escapes, the very subspoken of by Pliny as accompanying light-stance that sulphurous acid so easily dening. Schoenbein first told us that the stroys. We must therefore lift the whole smell was in reality that of ozone.

away before that action sets in. SchoenSulphurous acid, which is obtained by bein says that this acid oxidizes, and so burning sulphur, arrests the action of or- causes an oxidating influence on other ganized bodies, whether it be that smaller bodies to set in. This is sufficiently exmovement of decaying meat, or the more plained by the fact of its parting with its noble one of living man. It first deoxidizes, own oxygen. Mr. Higgin of Manchester but it gives off its oxygen easily, and acts as has used for many months sulphite of soda an oxidizer. It also acts as an acid, and dis- for his cattle, daily about two ounces. They solves animal matter. Its action is complex. have not suffered, although all around have It causes coughing, and it is in great quan- done so. One or two others have done the tities injurious to the lungs, but how much same with a similar result. Mr. Crookes in small quantities is not well known. It tried injection into the jugular veins of dispurifies the air of infectious matter, destroy-eased cattle of half-an-ounce dissolved in ing in a gaseous state, as it destroys putrid three ounces of water. They were better and living bodies subjected to it in a liquid for a while, but ultimately died. state, and it is therefore an excellent fumi- The salts of sulphurous acid are active gator. How much it brings of other evils disinfectants till they lose so much oxygen is an important question. It alters the air as to give off sulphur, and this occurs when of our towns entirely; every coal-burning much liquid is present. Some persons have town certainly is compelled to breathe it. observed the cattle which were dosed daily In vitriol-works men lose their teeth, but with about two ounces of sulphite of soda seem after a while to become accustomed to become much weaker. This has not alto the sulphur. How far the burning of sul-ways been the result. When the substances phurous coal is one of the causes of the great have not begun to putrefy, sulphurous acid decay of teeth, is a question which statistics acts as an antiseptic. of country and town teeth may answer. It is offensive in very small quantities, as is shown when gas burns with a little sulphur in it. Even a few grains burnt in the gas and continued during an entire evening are enough to annoy us, although the same amount rapidly burnt, and breathed only a few minutes, is less hurtful. True, all the discomfort arising from gas is not due to sulphur, as it has been proved that with incomplete combustion acytelene, a com

Chlorine is a great disinfectant, probably the most powerful agent for the destruction of organic structure, whether healthy or unhealthy. The latter is always most easily destroyed, as it is weak, and putrefying matter still more so, as it is already breaking up; and herein lies our protection: we may use just enough to destroy the decaying but not to injure that which is entire. passing through bleachworks, as we have done many hundred times, we have always

In

In fumigating, we find the senses to be the best judges; there ought to be in the air enough gas to give a very faint smell at most. As a preventive in common cases, it is enough if the smell is so slight that it is perceived only after coming from the open air. Nothing destroys liquid and solid putrid matter more rapidly than chloride of lime.

been pleased at the ruddy healthy faces of dropping occasionally a crystal of chlorate the men employed. This is no doubt due of potash into muriatic acid. When vile to the slight and constant smell of chlorine. smells are to be destroyed nothing is supeThis effect is seen at large paper-works rior to chlorine. The action is double: the where they bleach rags; but nature is al- chlorine combines with hydrogen and thus ways presenting us with new problems. If forms new compounds, but it also, as with we pass to the rag department, where the water, renders oxygen nascent, so that it is vilest portions of the filthiest clothes of Eu- a powerful oxidizing agent, and so oxygen, rope are assorted, we meet persons, at least with which we first began, again comes forin some cases, more wonderful in bulk and ward. in every symptom of healthy glow of life, than perhaps in any other place can be found. Perhaps butchers and brewers come nearest to them. The rags have long since undergone their putrefaction, and a something remains, perhaps animal matter, which has this wonderful effect. Statistics do not inform us if such people live longer. Perhaps, as with brewers, there is something dangerous in their prosperity. From De Muriatic and Nitric Acids. Guyton Neufville's Frankfurt tables, we do not find Morveau in 1773 recommended muriatic that either brewers or butchers had the acid as a disinfectant. This may be called highest term of life: theologians, sixty-the beginning of acid fumigation, not forfive; butchers, fifty-six; brewers, mer- getting the ancient use of vinegar, and the chants, fifty-six; brewers, fifty. Our own pretty well known action of acids. The tables do not place brewers in a high scale, muriatic acid was made simply by pouring and give workers in chemical works a high- sulphuric acid on common salt. It is power age, but the numbers are perhaps ques. erful, and the proposer has written an octionable. However this may be, the de- tavo volume on it of much interest; but structive power of chlorine is great. This even he gave preference to chlorine, which gas was discovered by Scheele in 1774. Foureroy introduced as a fumigating agent We cannot go to the ancients for its history, in 1791. Guyton Morveau was much agbut we may nevertheless believe that the grieved when Dr. Carmichael Smith used ancient Egyptians used it, consciously or nitrous acid at Winchester in 1780, and otherwise, as they evidently obtained nitric afterwards received a reward of five thouacid from their saltpetre, and this must have sand pounds from Parliament in 1802. He in their experiments been mixed with com- was glad to find that even in England men mon salt, thus giving nitrous gases and did him justice as the author of acid fumichlorine. In a Danish receipt, not much gation. It is interesting to see how men adafter the time of the discovery of this gas, mire the less valuable first. Nitrous fumes acid fumigation is recommended, the fumes are powerful disinfectants, but can to be obtained by pouring sulphur or nitric be used without great danger where there acid on common salt. The first gives mu- are living beings. We have heard lately riatic acid only, the second chlorine as of three deaths by exposure to these gases, even when they did not act powerfully on Chlorine decomposes readily salts of the senses. They are destructive, like chloammonia, thus destroying manures, and rine in all bad cases, but there do not apthis power is peculiarly shown by chloride pear to be cases where they are to be preof lime, and other of its alkaline com- ferred. The safest use of nitric acid is in pounds. At the same time a peculiarly the form of nitrate of potash, where we pungent gas is given off. It cannot there- know it preserves, or in the mode which fore be well to use it much with manures. received the recommendation of the AcaWhen it unites with lime it forms ultimately chloride of calcium, a very deliquescent body. It ought never, therefore, to be mixed with lime-wash.

stated.

It is made by pouring muriatic acid on peroxide of manganese. It is also made to flow very quietly by adding one and a quarter of alum cake or sulphate of aluminum, or potash alum to one of chloride of lime; also, as Mr. Stone recommends, by

demy of Dijon in 1767. We suppose that when they used it in ventilation the saltpetre was heated, in which case it would give off oxygen gas, which at first is very pure; afterwards nitrogen comes off, and the salt itself, or at least the base, is carried into the air, causing a very stifling sensation. The oxygen, however, would be valuable, and this plan might receive more attention. It is remarkable as having been tried be

fore the discovery of oxygen, which was in of this country must be owing to this con1774. When we can keep up a constant dition being found in it. Marshy or unstream of pure oxygen, active or less so, drained lands become cold and sour or by a self-acting process, we shall gain some peaty, and disinfect themselves. In warm new results. countries marshes are much more dangerHeat and Cold.-The gases spoken of as ous, and there we find cold an infecting oxygen, sulphurous acid, chlorine, and nit- agent. The night comes, and condenses, rous gas, are all destructive. Even muriatic like the bell-jar spoken of, and liquids with acid is so to a considerable extent. They poison in solution fall down as mist. Somemay be used to purify the air, because they times we find a little hollow of a field or diffuse into it, and leave no corner of the country filled with this vapour when the apartment untouched. All these disinfect plain is free. If any one ventures there he by destruction. There is a class of agents may be injured even if he be only a few which disinfects by preservation, if we may feet lower than his companions. We hear be allowed to speak so. These may be in hot countries of men who even receive called antiseptics. Boyle, who separated no injury standing, but suffer the fevers and chemistry from alchemy, began the modern ague of the district if they lie down. This examination of these bodies, and showed is an action of cold. The Innuit builds his the influence of heat and of cold. Cold pre- house of snow, and has only a small hole in vents the motion of particles: bodies great- it; he cooks and burns fat there, but we ly cooled cannot decay because the parts never hear of fevers and agues from putrewhen cold have no locomotion. Like a factive matter. The cold no doubt conregiment frozen in snow, they stand under denses it at once against the ice walls. the most powerful arrest. The influence Rain washes the air in a similar way, and has been lately called colytic, from the cold and wet certainly produce pure air. Greek word kwλów, to restrain. Animal If they exist in a country with good drainage matter seems capable of being preserved and little organic matter, they produce to endless time by cold: witness the frozen some of the most important conditions of elephants or mammoths of Northern Asia. health.

They have probably remained for ages, If we do not utter contradictions, we beand why should they change? The cold come one-sided; nature to us is full of removes putrid matter out of the air. Dr. them. Heat, like cold, is a source of health, Southwood Smith obtained a putrid organic and has a disinfecting power. In some liquid from the atmosphere of an unclean cases it is colytic. When the Damaras cut place, by passing it through a tube arti- meat into strips and dry it in the sun, the ficially cooled. Guntz put a bell-jar over decay is arrested by an act resembling putrid matter, and cooled it suddenly, when freezing. Dr. Henry showed that even if he obtained drops of a putrid liquid. Cold the poison of disease were contained in removes vapour, and with it matters which subtances, it was destroyd by heat. Vacremain suspended with it. No wonder, cine matter lost its power at 140° F., the then, that cold should prevent some dis- heat being continued for three hours. At eases. Cholera evidently avoids it. Cold 120° three hours did not destroy it. This acts also by preventing putrefaction even corresponds with the temperature of coaguwhen the particles are not arrested by lation. At this point something peculiar freezing. In all our thermometers we find happens to animal matter, and amongst temperate marked at 55° Fahrenheit (18 others it becomes cooked. Dr. Henry Cent.) A gentleman of our acquaintance always puts on a great-coat when the thermometer is under 56°. This is from independent experience. Putrefaction has been Heat expands bodies, and when the found to diminish to a mere trifle at 54°, fever matter is condensed over a marshy or close to it. Above that the gases begin region, the sun raises the vapour, and it is to arise. For this reason a place which diluted to such an extent as to become inis healthy at 53° may become unhealthy at nocent. Cattle-plague does not appear to 55°, and most persons will not remark the be diluted in this way, so as to become inchange of temperature. It is strange that this point in putrefying liquids should be, we may say, quite the same as the feeling of cold in the living body.

We must be thankful if in any district ill provided with means of purification, we have less than 54° heat. Much of the health

found it needful to heat the clothes of fever patients to 200° F. in order to produce disinfection.

nocent. Why should heat be called a disinfectant if it promotes putrefaction? It promotes putrefaction and its consequences, especially between 54° and 140°, but this must be in the presence of water. If it is dry heat, it arrests at all temperatures. Even if moisture be present, the disinfecting ac