THE LANCET, JULY 20, 1844. 517

LECTURESON

ORGANIC CHEMISTRY ;DELIVERED DURING THE WINTER SESSION, 1844, IN THE

UNIVERSITY OF GIESSEN.

BY

JUSTUS LIEBIG, M.D., PH.D., F.R.S.,M.R.I.A.,

Professor of Chemistry in the University of Giessen.

THE THEORY OF ACIDS.

GENTLEMEN,-In my last lecture I endeavoured topresent you with a clear and intelligible exposition of thetheory of COMPOUND RADICALS, the basis of organic che-mistry,-I now propose to explain to you the nature ofACIDS, and the manner in which they combine with BASES,in the formation of salts,-which will furnish us with stillfurther illustrations of the doctrine of compound radicals,by demonstrating that they are met with also in inorganicchemistry.

It is one of the most remarkable phenomena of che-mistry that certain compound substances, of a perfectlydefinite character, which we designate acids, enter intocombination with other compounds possessing a no lessdefinite character, termed bases, forming bodies in whichthe properties of both have completely and totally disap-peared. What, it may be asked, is the reason, in these I

cases, that the acid loses its distinctive characteristics ?What is the cause of its power of neutralisation ? Whatis the reason that this power is so remarkably varied asto the weight of the several bases required for the satura-tion of a given amount of acid ? The common theory ofthe formation of salts is not worthy of being called atheory,-it is nothing more, in fact, than the expression,or description, of certain processes. How can we call it atheory to say sulphuric acid and potass combined give ussulphate of potass? It is certain that we are obliged tobring together sulphuric acid and potass to form sulphateof potass. But do sulphuric acid and potass still exist inthe compound which results ? All the chemical reactionsof the compound prove that neither the characteristic

properties of the acid, nor those of the potass, are anylonger perceptible, and yet, notwithstanding, it is calledsulphate of potass !The principle proposed in the nomenclature of the

antiphlogiston system was, that the name of a compoundshould designate the substances which constitute its com-ponent parts.- From-the period of the introduction of that system itsnomenclature has been elevated to the rank of a theory.But it is a question at present disputable ; there are

persons who maintain that sulphuric acid and potass arereally existing in sulphate of potass. Now, I would ask,does this explain the power of saturation of the sulphuricacid or that of the bases ? Does it explain how, that, whenthey are brought into contact, they form together a neutralbody? Why, Gentlemen, it really explains nothing.This manner of designating compounds does not afford usthe slightest notion as to the mode and manner in whichthe elements of a salt are arranged, nor does it assist usin understanding the power of saturation of the acid.When you investigate the manner in which the constitu-tion of a metallic oxide influences its capacity of com-bining with acids, you will find the following facts.

(I shall employ here the nomenclature in ordinary use.)Suppose you have a metallic oxide containing one equi-valent of oxygen to one equivalent of metal, how muchacid do you require to neutralise it in order to form asalt ? If you take sulphuric acid, you will require oneequivalent. Thus, one equivalent of base containing oneequivalent of oxygen, as is the case with most metallicoxides, requires one equivalent of acid. A metallicoxide containing two equivalents of oxygen, requirestwice the amount of acid, and an oxide containing threeequivalents of oxygen to two equivalents of the metal,

re(ptiK&tMt&e the quantity of th& acM. The followingI. requires thrice the qu..an1iity of the acitl. The followingdiagram will render this manifest:-

’ Thus, for the capacity of bases to saturate acids, youhave here a definite point d’appui. It depends upon theamount of oxygen they contain; one equivalent of oxygenin a base requires one equivalent of acid to saturate it,two require two, and three, three.Now let us investigate the matter as regards acids.

Let us takeS.O2

Sulphurous acid 201 sulphur200 oxygen.When we combine this body with potass we obtain

S 02+K 0sulphite of potass. This proportion of sulphurous acidforms with potass a neutral salt.Now, I would inquire, does the oxygen of the acid in-

fluence its capacity of forming with potass a neutral com-pound ? No ; for when we add to the acid one equiva-lent of oxygen, the result is the formation of sulphate ofpotass.

the neutrality remaining undisturbed. Thus you perceivethat the addition of oxygen to the acid has no influenceupon its capacity of saturation.What, then, influences this capacity ? Is it the amount

of the sulphur ? No. Let there be an addition of sul-phur and you will obtain hyposulphite of potash,

another neutral salt.

Sulphite of potass, when exposed to the air, is con-verted into sulphate of potass, the capacity of saturationof the acid continuing the same ; there remains still aneutral salt. If we add more oxygen or more sulphurthe neutrality of the salt formed still continues undis-turbed. The amount of the sulphur may be increased to4 atoms, that of the oxygen to 5 atoms, so as to form anacid, the constitution of which includes a total of 9 ele-mentary atoms. Still the product

S4 O5+K Ois a neutral salt.

S, Oj+K 0

In these facts we have abundant evidence that neitherthe number nor the relative proportions of the elementsof what we denominate anhydrous acids, have the slightestinfluence upon the power of saturation, as we haveshown that neither the number of atoms of sulphur norof oxygen exercise any such influence upon the capacityof the acids to neutralise the potass.

Other examples may be adduced. Phosphoric acid isone of the most striking instances.Phosphate of soda

consists of phosphoric acid combined in what we call ?neutral salt, with 3 equivalents of base. You may ima-

gine that in this salt three atoms of soda are combinedwith one atom of phosphoric acid. How much phospho-ric acid, then, is combined with one atom of soda ? Athird. Let us write this down.

Each atom of soda is combined with a third of the phos-phoric acid.When you expose this salt to a red heat the properties

of the acid remain unaltered ; but you know that the pror-perties of the acid, under certain circumstances, undergoan alteration. For there is a phosphate of soda in whichone equivalent of soda is replaced by one equivalent ofwater. This is the ordinary phosphate of soda of com-

T a

518

merce. You know what happens when you expose thislatter salt to a red heat. The water, indeed, here takesthe place of a base, but not being a metallic fixed base, itis expelled in vapour. What becomes of that third of thephosphoric acid which we supposed was combined withthe water ? It enters into the composition of the remain-ing fixed salt. You have now a new acid, pyro-phosphoricacid, which has quite different properties from phosphoricacid. Phosphoric acid precipitates silver salts yellow,pyro-phosphoric acid precipitates them while.

If you isolate the acid of this soda-salt, which you havesubmitted to a red heat, you will find that it will expel fromall its combinations the other phosphoric acid, namely,that which precipitates silver yellow. It possesses, in fact,a far greater affinity for bases than the latter.Now, the properties of a third variety of phosphoric

acid are not less generally known than the former.

Meta-phosphoric acid is obtained from microcosmic salt.In this salt we have

One atom of soda and two volatile bases,-water andammonia,-which are both expelled by a red heat. Butthe phosphoric acid combined with these two bases is notexpelled, it combines with the remaining atom of phos-phate of soda,

A new acid has been formed,-meta-phosphonic acid,-thesalts of which contain to one atom of base three times asmuch phosphorus and oxygen as the common phosphates.Now, I ask, whence come these altered properties ?

This involves the same question as I have touched uponbefore, respecting the power of saturation of acids. If wewrite the formulae in another manner, the difference ofcomposition becomes at once evident. When expressedin relation to the same quantity of soda we have the fol-lowing:-

2 P 05+6 Na 0, phosphate of soda3 P 0,+6 Na 0, pyro-phosphate of soda6 P Og-)-6 Na 0, meta-phosphate of soda

In these three salts you perceive at once the difference ofcomposition; the formulae are exactly the same as theformer, only differently expressed.What is the difference between phosphoric acid and

pyro-phosphoric acid ? Pyro-phosphoric acid is a bodyof a higher order, the atom of which contains one-halfmore oxygen and phosphorus than the atom of phospho-ric acid.

Meta-phosphoric acid contains in its atom threetimes as much phosphorus and oxygen as the atomof phosphoric acid. A complex atom has here beenformed, which we may imagine contains in the same

space three atoms of phosphorus, and three atomsof oxygen more than the atom of phosphoric acid.That this, indeed, is the case, is evident from thefact, that all these salts may be reconverted into thecommon phosphate of soda, merely by adding soda,and exposing them to a red heat. Thus the expul-sion of water and ammonia-two volatile bases-has

produced alterations in which the saturating power ofphosphoric acid has been diminished. For two equiva-1 ents of phosphoric acid, in the first instance, you requiresix equivalents of soda. In pyro-phosphoric acid, thesesix equivalents of soda saturate three equivalents of phos-phoric acid, and in meta-phosphoric acid, even six equiva-lents of phosphoric acid.How can we explain these alterations of properties? It

is generally assumed that the expulsion of water andammonia is the reason, but is this really an explana-tion ? Is it not rather only a description of the pheno-mena ? The expulsion of water accompanies the altera-tions, but it certainly is not their cause. If it were so,the acid would be again immediately restored to its formerstate, when isolated, and again brought into contactwith water. But this is not the case. Thus you see the

change in the saturating capacity must be attributed tosome other cause. What I am desirous of directing your

’’

attention to in these examples and remarks is, that thenumber of elements of what we denominate anhydrous I

acids, has neither quantitatively nor qualitatively theslightest influence upon their saturating capacity.

This capacity is not increased by the addition of eithersulphur or oxygen to sulphurous acid, or of phosphorusor oxygen to common phosphoric acid. That these ele-ments have no influence whatever upon the saturatingcapacity of acids is further prored by certain other highlyremarkable phenomena. I mentioned in my former lec-ture formic acid ; the formula of this body i3

C, HO,assuming the acid to be anhydrous. It combines withpotass, forming formate of potass. Under certain cir-cumstances we see the oil of bitter almonds, a substancewhich manifests neither acid nor basic properties, enter-ing into combination by its elements with formic acid,

C2 H 03-i-Cia H6 O2forming a new acid.

Cl6 H7 05which neutralises the same quantity of potass as theoriginal formic acid ; thus, even in this case, the satu-rating power of the acid remains unaltered.

I have given you examples to prove that the additionof sulphur and oxygen to sulphurous acid, and of phos-phorus and oxygen to phosphoric acid, do not alter thesaturating capacity of these substances.

Here you have a case where the elements of a highlycomplex atom combine with the radical of an organicacid without producing any alteration in its capacity ofsaturation.

Now, I ask again, what is it which does exercise ailinfluence upon that capacity ? What is it that enables anacid to form a salt with a base ? I will bring before youbut one class of compounds, and you will immediatelyhave a clear apprehension of what we denominate a satu-rating capacity,-I mean the hydrogen-acids.

In these compounds there is no doubt as to the causeof the capacity of the acids to form salts with bases. Youknow what occurs when you bring a metallic oxide intocontact with a hydrogen-acid ; for instance, potass withhydrochloric acid. You know that the oxygen of thebase simply combines with the hydrogen of the acid,forming water; the chlorine of the acid at the same timecombining with the metal, forming a chloride:-

Upon what, then, does the saturating capacity of theacid here depend ? Upon the hydrogen it contains. Uponwhat does the property of the base (of the metallic oxide)of neutralising the acid depend ? Upon the oxygen itcontains. Two atoms of metallic oxide require twice asmuch hydrogen, and, therefore, twice as much acid-thedouble quantity of oxygen in the metallic oxide requiresa double quantity of hydrogen in the acid.

inasmuch as these acids decompose with the oxides, andbecause their hydrogen combines with the oxygen of thelatter, and the metals take the place of that hydrogen.To saturate such an acid with a metallic oxide is to

replace its amount of hydrogen by an equivalent amountof metal. Here we understand, at once, why the satu-rating capacity of the acid is entirely independent of theradical, no matter whether this be chlorine, bromine,iodine, cyanogen, &c. The power of neutralisation islimited by the amount of hydrogen. If this amount is one,two, or three times as large, the acid requires one, two, orthree times as much oxide. I maintain that the radicalhas not the slightest influence whatever; it is the hydro-gen alone.Take sulphuretted hydrogen, i.e. hydrosulphuric acid,

combine it with sulphuret of carbon,

519

-

In this combination the radical of the acid, namely, the

sulphur, is increased by twice its amount more, and,moreover, one atom of carbon is superadded, but doesthis alter the saturating capacity of the acid ? No ; forthis is not dependent upon the sulphur, as we have seen,but upon the hydrogen.Take hydrocyanic acid, combine with its radical two

atoms of sulphur or two atoms of oxygen. Does this alterits saturating capacity? No. This can only alter withits amount of hydrogen.

You will now understand that the phenomena of the for-mation of salts,-the property of acids of neutralisingbases,-of oxides to saturate acids, depend upon the hydro-gen of the acid. Upon this point we possess in the hydro-gen-acids a definite idea, an irrefragable proof:-theirhydrogen may be replaced by metals.Now, it may be inquired, is not the case precisely the

same with the oxygen acids ? Can it not be proved thatthe properties of the oxygen acids, which are so remark-ably analogous to those of the hydrogen acids, dependupon the same cause ? In point of fact, when you bringa metallic oxide, containing one equivalent of oxygen,into contact with an hydrogen acid, you know what willresult: you had a metallic oxide, you obtain a correspond-ing chloride, iodide, &c. The hydrogen compound herepossessed an acid character which is destroyed by thesubstitution of a metal for the hydrogen. To expect thatthe new compound should possess the same properties asthe original acid would be most unreasonable. Thechloride formed is very different, of course, from the hydro-chloric acid.Now let us contemplate, that in one atom of a metallic

oxide, containing one equivalent of oxygen, this oxygenis replaced by one equivalent of chlorine, when broughtinto contact with an hydrogen-acid. Take a metallicoxide containing two equivalents of oxygen, bring it intocontact with an hydrogen acid, such as hydrochloric acid,what will be the chlorine compound produced? ’! A cor-

responding metallic chloride. Take an oxide of the thirdclass (two atoms of metal, three atoms of oxygen), whatwill be the product ? A compound in which you will findtwo atoms of metal combined with three atoms of chlo-’Pl1’"’1F!1

And is this not the same, we may ask, with the oxygenacids ? Let us compare chloride of potassium with sulphateof potass.

You have, in both, the same amount of potassium, but inthe sulphate of potass you find the chlorine replaced by acertain amount of oxygen and of sulphur. Chlorine is aradical; we think it is a simple substance, but we do notknow that it may not be decomposed to-morrow.

In the combination of sulphur and oxygen we have acompound acting completely the part of chlorine. The

properties of the potass are equally destroyed by hydro-chloric acid and by sulphuric acid; chloride of potassiumis a neutral body, so is sulphate of potass. Ifwe are war-ranted in inferring equal causes from equal effects, wemay assert that the sulphate of potass is a compound ofpotassium and a compound radical, constituted by sul-phur and oxygen, and performing functions completelyanalogous to those of chlorine.

Contemplated in this point of view, what do we findwith respect to the compounds of sulphuric acid withother oxides containing more than one equivalent of oxy-gen ? One equivalent of potass combined with one equi-valent of hydrochloric acid produces one equivalent of ametallic chloride. One equivalent of potass with sul-phuric acid forms the substance which is designated.

and in this we assume that the chlorine is replaced by acompound body performing the functions of chlorine.Now, what is the case with those oxides containing twoatoms of oxygen ? It is exactly the same as in the formercase. We obtaina substance containing, to one atom of the metal, twoatoms of this compound radical. With the compoundsof oxides of the third series, such as persulphate of iron,sulphate of chromine, we have three atoms of the radicalI fn twn HtnnDs nfthp. mptal-And thus, throughout the series, the analogy is complete.

In most of the so-called oxygen salts the metal may bereplaced by hydrogen, and you obtain compounds com-pletely analogous in properties to hydrochloric acid.From sulphate of potass, oxalate of potass, nitrate ofpotass, you obtain the following :-

According to the common theory, these acids are not com-pounds of hydrogen with compound radicals, but combi-nations of water with what are called anhydrous acids.They are considered to be hydrates of these anhydrousacids. This theory is so far consistent as it adapts theidea of the constitution of a salt to that of an acid. In

sulphate of potass there are contained potass and sulphu-ric acid,-so says this theory-because, in order to formthe salt, we must combine sulphuric acid with potass.Hydrated sulphuric acid contains sulphuric acid and

water, as I can form this substance by bringing water intocontact with anhydrous sulphuric acid (S 03), Accord-ing to this view we must express the formulae given above

i as follows:-

, But how, we may ask, are these so-called anhydrous

acids known? Can we exhibit them without this water

of hydration ? The following strange answer is returnedto the question by the adherents of this theory -" Theinnumerable acids which we call anhydrous exist only inimagination; they are quite unknown,-they cannot beshown to you."The idea that the common oxygen acids are hydrates,

has originated in the fact that two oxides, of the highestdegree of oxidation of sulphur and phosphorus, form,combined with water, our common sulphuric acid andphosphoric acid. Resting upon experience in these in-stances, the assumption that water entered into the for-mation of the other oxygen acids was considered justifi-able. But, most strangely, these two oxides, theseso-called anhydrous, sulphuric, and phosphoric acids, donot possess any of the characteristic properties of acids ;these they obtain only by their combination with water.In the compound which we denominate hydrated sul-

phuric acid, and which possesses properties analogous tohydrochloric acid, we have one equivalent of hydrogen,four equivalents of oxygen, and one equivalent of sulphur.

Which of these four atoms of oxygen is combined with thehydrogen, forming water ? and which with the sulphur,forming the sulphuric acid ? No one can answer thisquestion, even could he see, by means of the microscope,the’atoms lying side by side, since one atom of oxygen mustof necessity have the same size and shape as the other.We assume that it is not a single atom of the oxygen

which is combined with the hydrogen, but four atoms ofoxygen and, moreover, one atom of sulphur. We assumeas true nothing but what has been proved, and this is theonly reasonable way of employing our faculties in the in-vestigation of nature. There is no proof that our common

520

sulphuric acid contains water, but we can prove that itschemical character-analogous to that of hydrochloric acid-depends, as in that acid, upon the presence of hydrogen.We can prove that this hydrogen can be replaced by itsequivalent of metal.When we combine a metallic oxide with hydrochloric

acid the result of the combination is the formation of ametallic chloride, and for one equivalent of oxygen inthe oxide, one equivalent of water is separated; for twoequivalents, two of water, &c. All this we observe to bethe case with the so-called hydrated sulphuric acid.There is not the slightest difference to be observed in thechemical phenomena of the formation of salts. We assumethat in the decomposition of sulphate of potass by chlorideof barium a simple exchange between the metals takesplace.—

Chloride of potassium;whilst according to the usual theory the barium is firstconverted into oxide of barium at the expense of the oxideof potassium, and only then obtains a capability of com-bining with the sulphuric acid :-

We assume that when precipitating copper (by means ofiron) from a solution of salt of copper, the latter metalsimply takes the place of the former.

The common theory supposes that the oxide of copper isfirst reduced by the iron, and then only is the proto-sul-phate of iron formed.

I believe that it can be directly proved that the metalsdo not exist in these salts in the state of oxides. Pro-fessor Kopp has definitively proved, by a comparison of £the specific weights and the atomic volumes, that theoxide of potassium in the sulphate of potass, and the waterin the hydrated sulphuric acid, have ceased to exist as

oxide of potassium or as water; that the water exists in thehydrated acid as a hydrogen compound ; the potass inthe sulphate, as a potassium compound, in which theelements of the anhydrous acid have united with the oxy-gen of the potass, or of the water. Professor Daniell hasarrived at the same conclusion from a more minute investi-

gation of the decomposition of salts by the electric current.

ON THE ERRORS AND MISCHIEFS OF THESOUND AND CATHETER,

AND ON THE

NATURE AND TREATMENT OF URINARYSTRICTURE.

By T. WILKINSON KING, F.R.C.S.E.

Strictures ’I’adahle. Urethral cicatrix, how obstructive.Authors’ cases. Statistics. Capillary injections sponta-neously subside or yield to regimen, c.

T’HE present object is to extend and enforce the viewsformerly advanced.* It may be premised, however, incase the plan pursued should be deemed objectionable,that this course was, in a manner, imposed on me by thedifficulties in which the subject appeared enveloped by itsmost esteemed expositors. All writers on permanentstricture seem regardless of the fact that the serious diffi-culty of the case is always transitory, returning or in-

* Vide pages 389 and 629 of the preceding volume ofTHE LANCET.

creasing every other week’; still less mindful do theysee that simple settled contractions of the urethral liningare, in the main, totally harmless, and only to be rankedamong the slight and rarer cases of retention of urine.

For a summary of what has been already advanced,we have inferred, first, local capillary excitement;secondly, general, humoral (catarrhal), and variabledisturbances, increasing the local affection, as it were,by irregular leaps, sometimes an acute inflammatoryobstruction being superadded ; thirdly, thickening com-plicates the injection, and then the two variously andvaryingly complicate each other; fourthly, settled con-traction and hardening may follow.The aims are to put an end to the bodily disorders and

to the relapses of local injection, and to absorb or wastehypertrophy. It is to be remembered that stricture is

hardly ever entirely cured, and that local irritation, notto say violence, is not only needless but mischievous.

I do not scruple to assume that all common stricture,which is variable, is essentially vascular and inflamma-tory, and not muscular and spasmodic.* I do not thinkit necessary to assert that inflammatory or even simplespasm may never occur in Wilson’s muscles, or the com-pressor of the bulb, but I am of opinion that those whohave most advocated spasm are the least calculated todiscriminate the real cause of muscular obstruction.Dupuytren circumcised the anus and seared the part

with iron heated to whiteness, and the urethra becameobstructed for a day or two. Here I conceive tumefac-tion to have been much more certain than sympathy orspasm. Does the spasm of cystitis yield to dilatation orto rest? What is tenesmus but inflammation and motion?Does stretching cure the contracted sterno-cleido mas-toideus ?

Is it not plainly natural to set aside spasm and to sub-stitute capillary action in the following ?" The permanent stricture consists in a thickening of

structure, whereby the diameter of the diseased part ofthe passage is lessened. However, the diameter of theaffected portion of the canal even now varies, according asthe spasmodic action of the muscles about the perineum andthe effects nf inflammation contribute more or less to atemporary increase of the obstruction. In the languageof Sir Everard Home, the case may be both a permanentstricture and a spasmodic one ; permanent, because thediseased part of the urethra is always narrower than therest of this passage; and spasmodic, inasmuch as thestricture may be rendered still more contracted by spasmaffecting the muscular structure, whatever that may be,adjoining the disease."t There is nothing, surely, herebut old inflammatory thickening and variable catarrhalinjection. Hunter says, speaking of the spasmodic, per-manent, and varied cases, " most obstructions to thepassage of the urine, if not all, are attended with nearly

’ the same symptoms, so that there are hardly sufficient’ marks for distinguishing the different causes."t

There is a stage of stricture between that of transitoryinjection and that of corrugation, though it is but rarely

, met with in any remarkable degree or wide extent. I’

mean a condition of solid tumid thickening. I believe

very much of this may permanently subside. The finalcontraction may affect the entire canal, or the smallestpart of it, longitudinally, transversely, or obliquely.

Sir B. Brodie says (last edition, p. 6), " It must be ac-knowledged that the existence of a purely spasmodicstricture is of rare occurrence. Repeated attacks of thespasmodic contraction, attended with violent efforts and

’

straining, to evacuate the contents of the bladder, cannotfail to lay the foundation of permanent thickening ofthe mucous membrane, and, at all events, there can be

3 ..———_-——————————————————————————————

The 11 British and Foreign Quarterly Review" for, Jan. 1844, p. 207, says, ’ We very much doubt even the’ occasional existence of" spasmodic stricture, but (p. 213), caustic cures by modifying the" sensibility" of thet canal, and merely " blunting the sensibility, in many- cases facilitates the passage of a large instrument."- What has the cause of spasm to do where spasm does not- come?f t Cooper’s Dictionary, p. 1322.

j t Palmer’s edition, vol. ii., p. 229.