RECORD OF MEDICAL SCIENCE.
CHEMISTRY.
On Some of the more Important Chemical Disinfectants. By George
Wilson, M. D., F. R. S. E., Hon. Member of the Pharmaceutical So-
ciety of Great Britain.—1 consider it an acknowledgment due from me
to the Pharmaceutical Society of Great Biitain, which has honored me
with its diploma, that 1 should contribute a paper to the proceedings of
its Edinburgh section, with which I stand more immediately connected.
I have selected a subject, of special interest at the present moment,
■when we have reason to apprehend the appearance of cholera on our
shores, but which is at all times a subject not less important than it is
difficult. To discuss the entire question of disinfection would require
many papers. I can only refer at present to some of its relations.
The term disinfectant, in strictness of language, can only be applied
to those agents or substances which destroy or decompose infectious or
contagious matter. But it is usually employed in a wider sens?, so as
to include, not only disinfectants proper, but likewise antiseptics and
deodorisers. Any attempt to draw a sharp line of demarcation between
these three classes of agents, is rendered impossible by our almost total
ignorance of the nature of contagious matter. Some substances, such as
chlorine and sulphurous acid, possess at the same time, disinfectant,
antiseptic, and deodorising powers. Some, like common salt, are
probably simply antiseptic; of others, such as the salts of the heavy
metals, which are in high repute as deodorisers, it may be questioned
whether they are of any value as disinfectants, although with some
persons they rank at the head of the list. Without insisting at present
on this, it may suffice to define the bodies we are about to consider, thus :
A disinfectant is an agent which effects the chemical decomposition of
organic poisonous matter—the term poisonous being used in a wide sense
to include all the known or supposed causes of the development of disease,
which are referred to under the names of miasma, malaria, infectious
virus, contagious ma*ter, &c.
An antiseptic is an agent which prevents or arrests the development
of organic poisonous (or non-poisonous matter) without effecting its
chemical decomposition.
A deodoriser is a substance which destroys odor, by decomposing or
combining with, or absorbing odorous matter. Chlorine, for example,
decomposes sulphuretted hydrogen, whilst a salt of lead combines with
it, and charcoal simply absorbs it.
Before considering the relative merits of particular substances belong-
ing to these classes, it is necessary, however, briefly to discuss the im-
portant question—does the poisonous organic matter which occasions cer-
tain diseases, occur in the solid, liquid, or gaseous form ? The certainty
that prolonged exposure to a vitiated atmosphere, such, for example, as
that of a fever ward, produces disease, has led to a conclusion in which
probably all concur, that the air is one of the chief media through which
disease is propagated, and this connexion has in turn led to the much
more doubtful inference that infectious matter is truly gaseous or vapor-
ous. This view lias probably been strengthened by the recent extensive
study of the properties of anaesthetics, and by- the many observations
which have been made on the rapid and powerful action on the body of
substances which enter it through the lungs. It has certainly also been
deepened by the opinion, widely prevalent, that the gases which are
evolved from cesspools, sewers, and stagnant waters in general, particu-
larly sulphuretted hydrogen, hydrosulphuret of ammonia, and marsh
gas (light carburetted hydrogen) are the direct and specific causes of
ague and fever.
If this opinion were well founded, the limits and best modes of ap-
plying disinfectants could be determined without much difficulty, and
our control over infectious diseases would certainly be much greater than
it is,.
I think, however, that we may with confidence affirm that the great
majority of diseases are not propagated by gaseous poisons. The recent
tendency to advocate an opposite opinion, has been mainly occasioned, 1
believe, by an opinion expressed by the late Professor Daniell to the ef-
fect, that the fatal fever of the African coast is occasioned by sulphuret-
ted hydrogen. This view was founded on an analysis of water brought
from that coast, and determined the ventilating arrangements fitted up
in the vessels which formed the disastrous Niger Expedition. It ap-
pears to have been extensively adopted by medical men.
During the frequent prosecutions for nuisance, under the new police
act, which took place in this city and elsewhere, during the last visita-
tion of cholera, it occurred to me, and to other chemists, to be constantly
met by endeavours on the part of the prosecutor to compel an ac-
knowledgment that sulphuretted hydrogen, hydrosulphuret of ammonia,
and marsh gas or light carburetted hydrogen, which are confessedly
given off by sewage waters, are the direct causes of fevers and other
diseases. So long as this idea prevails, and men rest satisfied with it,
as the true explanation of the mode in which fevers and similar mala-
dies originate and are disseminated, they will cease to prosecute inquiry
into the matter. It is most important, therefore, to discountenance the
notion that we are acquainted with the true materies morbi.
That neither sulphuretted hydrogen nor hydrosulphuret of ammonia
produces any special disease, may be sufficiently demonstrated by the im-
punity with which persons are known to expose themselves to much
larger quantities of these gases than can possibly act on those who suf-
fer from exposure to marsh miasmata. In these, the nicest tests have
failed to give the slightest indications of sulphuretted hydrogen, and
yet a few hours exposure to such miasms has been enough to develop fe-
ver. On the other hand, in every analytical laboratory, sulphuretted
hydrogen and hydrosulphuret of ammonia are daily respired for weeks
or months together by those engaged in analysis, yet analytical chem-
ists certainly are not specially subject to fevers. At the Bonnington
Chemical Works, where the ammoniacal liquor from the Edinburgh Gas
Works is largely converted into sulphate and muriate of ammonia, the
workmen are exposed to the hydrosulphuret of ammonia, which forms
so considerable a part of the liquor, and when it is neutralized with sul-
phuric and muriatic acid, sulphuretted hydrogen is given off in such
abundance as to blacken the silver coins and watches on the persons of
the bystanders, and even (along with the carbonic acid simultaneously
evolved) to render them temporarily insensible if they incautiously re-
spire the gases. Yet no special malady is known to result from this ex-
posure, and the Bonnington Works enjoy the reputation in the neigh-
borhood of protecting it from the inroads of endemic and epidemic dis-
eases. Similar observations as to the non-deleterious effects of exposure
to comparatively large volumes of sulphuretted hydrogen have been
made at the metal works, where a superficial tarnish of metallic sul-
phuret is removed by washing with acids, and the workmen are freely
exposed to the sulphuretted hydrogen evolved. I need not say, that I
do not wish to affirm that this gas or its combination with ammonia, is
not a powerful poison, if respired alone, or to deny that the continued
entrance of either into the body, must debilitate it and prepare it for
yielding to the attacks of disease. But that it is the cause of the fevers,
which a very short exposure to the so-called malaria of certain districts
infallibly occasions, I altogether disbelieve.
The alleged noxiousness of diluted marsh gas (light carburetted hy-
drogen), admits of more easy disproof, for were it the deadly agent it
has been declared to be, our colliers, who are exposed in coal pits to
much larger volumes of it than any other class of persons, should be to
a corresponding extent sufferers from the diseases which it is supposed
to occasion; but, unless when its mixture with air explodes, it is desti-
tute of any injurious action on the pitmen, who are a healthy class of
the community.
Another disease—namely, influenza—has been imputed by high chem-
ical authorities to the diffusion through the atmosphere of a peculiar
gas; Dr. Prout regarding seleniuretted hydrogen as its cause, Schiin-
bein attributing its production to ozone. There is no evidence that
either of these views is true, but much may be said in favor of the lat-
ter. The last severe epidemic of influenza spread over Europe with a
rapidity which almost seems to point to a gas as the medium of its
propagation. No one, however, has detected seleniuretted hydrogen in
the atmosphere; and air largely impregnated with ozone may be breathed
with an impunity which throws grave difficulties in the way of Schbn-
bein’s hypothesis.
Whilst thus, with the exception of influenza (if it is be excepted,) no
gas is known to possess the power of developing an infectious or conta-
gious endemic or epidemic ; on the other hand, as Professor Graham has
justly remarked, such infectious matters as are accessible to us, for ex-
ample, “ the matter of cow-pox, may be dried in the air, and is not in the
least degree volatile. Indeed, the volatility of a body implies a certain
simplicity of constitution and limit to the number of atoms in its inte-
grant particles, which true organic bodies appear not to possess. Again,
the source of such bodies being at all times inconsiderable, they would,
if vapors, be liable to a speedy attenuation by diffusion so great as to
render their action wholly inconceivable. It is more probable that
matters of contagion are highly-organized particles of fixed matter, which
may find its way into the atmosphere, notwithstanding, like the pollen
of flowers, and remain for a time suspended in it.”
To these statements it may be added, that all chemists now acknow-
ledge that volatility is not essential to the transference of solid bodies to
the atmosphere, at least so far as those soluble in water are concerned;
for observations on the largest scale have shown that the vapors of vola-
tile liquids carry with them sensible quantities of all the solids which
they dissolve ; common salt, nitrate of potass, boracic acid, phosphoric
acid, afford marked examples of this; but the list of salts soluble in
water which accompany its vapor at temperatures at which when dry
they are fixed, is endless. * The significant word “ Malaria” therefore,
• In virtue of this we may anticipate the administration of other medicines
than anaesthetics by the lungs, although they may not be volatile. In cases of
poisoning it would be of the greatest importance, if we could directly transfer to
the blood an emetic or purgative, which we may hope to do along with the
vapor of its solvent, aqueous or non-aqueous. Such a process, however, would
be applicable only to medicines which act powerfully in small doses.
which embodies in a single term the evil reputation which the air or
atmosphere has acquired, as the vehicle of contagion, may still, if we
choose, be retained, although we acknowledge that all accessible conta-
gious matters are non-volatile liquids or solids. It may further be added,
that with the questionable exception of influenza, no endemic or epi-
demic spreads with the rapidity and equability, so far as area of occur-
rence is concerned, which would characterize it, if it were occasioned by
a gas subject to a force so powerful as that of gaseous diffusion. Pro-
fessor Graham’s argument is still more cogent, for, according to his
views, if infectious matters were truly gaseous, we should never have
endemics or epidemics, unless those matters were developed in immensely
larger quantities than by universal acknowledgment they are. In truth,
they elude every test, even when applied to large volumes of the most
infected atmospheres.
From all that has been stated, it must be inferred, according to our
present knowledge, that, at least the great majority of the substances
which are intended to be reached by disinfectants, are not volatile, and
therefore are much less easily decomposed than if they were gases. We
may also with reasonable confidence affirm, that they are organic pro-
ducts, and as such consist of carbon, hydrogen, oxygen, and nitrogen,
or at least- of two (if not always of three) of these elements; and that,
like all such compounds, they are readily decomposed by chemical re-
agents, especially oxidizing ones. There is no reason to imagine that
infectious matters are difficult to decompose, provided we can reach
them. The difficulty lies in reaching them. Assuming then that con-
tagious matters are not volatile, and that they contain (to take the most
complex case) carbon, hydrogen, oxygen, and nitrogen, the principles
which are to guide us in the application of chemical disinfectants, will
not be far to seek. Oxidizing agents will plainly be of great value as
they can readily convert hydrogen into water, and carbon into carbonic
acid, and thus disintegrate and destroy the morbific matter. Substances
having a great affinity for hydrogen, such as chlorine and its class, will
plainly also be of great service. Substances having an affinity for
oxygen will also be applicable to the destruction of organic poisons; and,
finally, all reagents which by contact with organic matter can determine
a new arrangement of its ultimate elements. All the powerful chemical
disinfectants act in one or other or all of those ways. I shall refer to
five of the disinfectants : 1, quicklime, including caustic potash and
soda; 2, nitric acid; 3, chlorine; 4, aqua regia; 5, ozone. The vaiue-
of quicklime and of the caustic alkali.es as disinfectants, has certainly
not been overrated, although it may be questioned whether our sanitary-
authorities have been wise in trusting to lime alone as a purifier. From
the careful study of the process of natural and artificial nitrification, and
from the results of the application of soda lime in organic analysis, we
have learned that the caustic alkalies and alkaline earths decompose
organic matter with the evolution of ammonia, which by oxidization
may become converted into nitric acid. Woodwork or stone floors, to
which a coating of limewash cannot be applied, requires only to be
washed with caustic soda or soft soap, to obtain an effect identical with
that which lime occasions.
2.	Nitric Acid seems latterly to have fallen into disrepute, but cer-
tainly undeservedly. It acts more rapidly on many organic compounds
than chlorine does, attacking their carbon as well as their hydrogen, and
as it is not required in large quantity its application is not costly.
3.	Chlorine.—Of chlorine, which is at present the favorite disinfec-
tant, it is needless to speak. Its peculiar power of decomposing com-
binations of hydrogen, gives it, in one respect, a superiority over nitric
acid, which does not decompose many of the gaseous hydro-carbons; but
it should not be forgotten that it is only in the presence of light that
this action of chlorine is fully displayed, so that its disinfectant influ-
ence is comparatively small in the case of dark or ill-lighted apartments,
such as underground cellars, the lower cabins, or the hold of a ship,
which are the very places where disinfectants are often most wanted
4.	Aqua Regia, as uniting the properties of nitric acid and of chlo-
rine ; each of which has peculiar virtues, the former in particular being
a wonderful oxidizing agent, the latter possessed of a great decomposing
action over hydro-carbons, appears entitled to a high place among dis-
infectants. It can be cheaply procured by pouring oil of vitrol on a
mixture of nitric acid and common salt, or by heating a mixture of
nitric and muriatic acids.
One of the most rapid and effectual methods of disinfecting a large
empty apartment, such as an hospital ward, would be to place in one
corner a vessel containing the materials for chlorine, such as oxide of
manganese and hydrochloric acid, or oxide of manganese, common salt,
and oil of vitrol; and in another corner a vessel containing nitric acid
and a few fragments of copper, so as to evolve nitric oxide, which would
spread through the apartment and form nitrous acid there, oxidizing
everything oxidizable which it contained, whilst the chlorine specially at-
tacked the hydro-genous compounds. The walls might then, if neces-
sary, be lime-washed, with a view alike to destroy any adhering organic
matter which had resisted the action of the gases, and to neutralise any
traces of free acid.
5.	The last of the disinfectants proper to which I refer is the singu-
lar substance ozone, which has a special interest, as being in all proba-
bility the great natural disinfectant. Jts nature is still matter of spec-
ulation. Scbiinbein, its discoverer, regards it as a peculiar oxide of
hydrogen; Berzelius and Faraday represent it as simple oxygen in a
peculiar (or allotropic) state of modification; it has been suggested that
it is an oxide of nitrogen; and quite recently M. Fremy has affirmed it
to be what he calls “ electrized oxygen,”—i. e., oxygen modified in pro-
perties by the action of electricity upon it; a view not materially differ-
ing from that of Berzelius and Faraday. There are difficulties in the
way of all these views, into which it is not necessary to enter. All
thatconcerns our present subject is that, by different processes, a substance
can be developed in the atmosphero which possesses remarkable disinfec-
tant and oxidizing properties. The oldest known method of producing
the so-called ozone, is the exposure of air to a stream of friction or high
tension electricity. Its odour may always be recognized in the neigh-
borhood of an electrical machine whilst at work. Another method is
the galvanic decomposition of water, when the ozone accompanies the
evolved oxygen. A third, and the most convenient method on the
small scale is the exposure of phosphorus in moist air. By these pro-
cesses and certain others, air is made to acquire a striking power of oxidi-
zing, bleaching, deodorizing, and disinfecting. We cannot doubt that
every thunder-storm developes some ozone, and other processes also
probably produce it. At all events the atmosphere frequently exhibits
an oxidizing and bleaching power, at other times absent, which Scbon-
bcin, Faraday, and others, attribute to the development of ozone within it.
No one who has experimented on ozone will doubt its potency. I re-
fer to it here because there are so many reasons for believing that it is
the agent which prevents the accumulation in the atmosphere of volatile
organic bodies, by converting them into water, carbonic acid, nitric acid,
and ammonia, that we cannot avoid looking hopefully to it as destined
to prove our disinfectant par excellence. Certain as we are that for
thousands of years miasmata, malaria, poisonous effluvia, and every
gas, vapor, and volatile body developed at the surface of the earth, must
have found their way into the atmosphere, and that nevertheless its
purity is not sensibly affected, we must regard the constituent or condi-
tion of the air, which has secured its purity during centuries, as one
demanding special study. Further this constant process of disinfection
has not interfered with the respiration of animals, so that we may fairly
regard ozone as a substance applicable as a disinfectant in places occu-
pied by human beings or by the lower animals. It is true that the power
of producing influenza or catarrh has been attributed to ozone in
excess; on grounds, however, almost entirely speculative. This view
may or may not be true ; but of this I am quite certain, that the well
known impunity with which electricians expose themselves for hours
together to the action on the atmosphere of large friction machines,
which the dullest nostril can discover to be producing abundance of
ozone, is enough to show that a large impregnation of the air with this
substance, neither affects respiration nor produces catarrhal affections.
We ought, therefore, I think, to give special attention to ozone. It is
not likely that we shall be long without discovering new processes for
its production. It will be specially valuable for what are the most im-
portant, and, at the same time, the most difficult occasions for disinfec-
tion—namely, where human beings cannot be removed from infected
apartments. Examples of such cases are found in a large ship at all
times, and still more when its crew and passengers are attacked by dis-
ease ; in the wards of an hospital, from which the sick cannot be taken;
and perhaps most strikingly in a large factory, where hundreds of per-
sons assemble daily together, many of most uncleanly habits, and at
epidemic seasons fresh from infected rooms, whilst the apartments con-
tain valuable metallic machinery, and fragile silk, cotton, linen, or
woollen goods, which interpose an additional obstacle to the free em-
ployment of gaseous disinfectants. The condition of our ships as re-
gards ventilation and wholesomeness is proverbial; and on inquiry of
residents in Manchester and Glasgow I find, that where disinfection has
been attempted in factories—which it rarely has—it has consisted in
sending a man once a’day through every room with a quantity of blaz-
ing pitch, which was supposed to fumigate into purity the atmosphere,
whilst it set all the workpeop’e coughing.
How difficult it is to prevent the spread of erysipelas, gangrene, fever,
and the like in hospitals, every medical man knows too well. Ozone
at least deserves a trial as a disinfectant in such cases.
Antiseptics.—The only antiseptics to which I shall refer are two.
The first is sulphurous acid; it is a powerful antiseptic, for it resists tho-
roughly the decomposition or decay of organic matter. In reality, how-
ever, it as much resists the development as the decay of organic bo-
dies, and thus it doubly prevents the evolution of organic poisons. Dr.
Christison long ago pointed out how small a quantity of this acid is
sufficient to destroy plants. In the wine countries it has been used from
time immemorial to prevent the souring or acetification of the lighter
wines, when kept in casks partly filled. Professor Graham, who strong-
ly recommends it as a disinfectant, draws attention to the fact that at
Manchester the offensive effluvia of the cochineal dye-vats, which resist
the action of chlorine and nitric acid, are at once destroyed by sulphu-
rous acid. My own attention was directed to it from the employment
of it on a large scale by paper-makers and others to secure the prepara-
tion of pure gelatine, a substance peculiarly liable to enter into putre-
faction. Sulphurous acid can be easily prepared by burning sulphur,
or by heating oil of vitriol, along with charcoal or vegetable matter.
Its corrosive action is very slight; its disinfecting action very powerful.
The sulphite of soda is now prepared in quantity at different chemical
works. The addition of a stronger acid sets free the sulphurous from
its salts. As to its mode of action, if we concur with Liebig in be-
lieving that morbific matters resemble ferments in being active, only
whilst undergoing a decomposition which is mainly determined by the
oxygen of the air, we may suppose sulphurous acid to render the poi-
sonous matter iuert, by preventing its oxidation. This acid, moreover,
is a powerful deoxidizing agent, and it may be by removing oxygen from
organic poisons that it renders them inert, by decomposing them.
Further, sulphurous acid can combine with certain elements of organic
bodies, as we see in its temporary bleaching action on vegetable colors;
and it may be thus that it neutralizes morbific matters. In one or other
or all of those modes, this agent may act as a disinfectant; but at all
events its action is very powerful, and it deserves much more attention
than it has received.
The only other substance to which I shall at present refer, is pitch
oil, one of the products of the distillation of tar. It is an antiseptic
of the most powerful class, and very cheap, and if not used in excess, it
is applicable as a deodorizer; but its own strong tarry smell interferes
with its extensive use.—Pharm. Jour.