Obrazy na stronie

Oct. 27, 1865.
College of Physicians.

197 consequently, which the lowest temperatures tend to It must, moreover, be observed that magnetic oxide of produce.

iron and magnetic pyrites possess, like tempered steel, Ferrosum changes readily to ferricum (iron of peroxide). permanent magnetism. This property, common to both This property corresponds to that presented in ché- natural and artificial loadstones, independent of the mistry by pyrophoric iron and protoxide. It furnishes state of oxide, of sulphide, or of carbide, must then result in this way steel and malleable iron; but, when not from the simultaneous presence of two allotropic conarrived at the condition of blistered iron, it retains ditions of iron, which is the only constitutive element under these two forms the power, always well deter- common to these very different bodies. mined, of being changed, by the usual metallurgic reac- The two allotropic conditions of iron, proceeding from tions, from iron to steel and from steel to white crystal- the two oxides, are then present in metallurgy, with a line cast-iron.

similar system of variations; but they are rendered disThe physical characteristics of ferrosum when com- tinct by a certain number of properties. Besides which, bined with carbon, are hardness and fragility.

they may go through most of the metallurgic reductions From its chemical properties it should be ranked and transformations, without losing their original characamong the bodies which combine with a single atom ofteristics, or being confounded one with another. These oxygen.

phenomena present the most complete analogy with the Ferricum is the metal of anhydrous peroxide ores. Its wellknown properties of the two tartaric acids, distin. metallic type is the iron produced from these ores. It guished by the direction in which they deviate from the unites with carbon at high temperatures, but the latter is plane of polarisation. deposited during slow cooling for want of affinity. This The study of the calorific capacities of various pro-condition corresponds to the high temperatures, like that ducts furnishes results which prove, between crystallino of welding heat.

cast-iron and certain malleable irons, numerical differIt gives malleable iron, and as a variation of form, ences too important to be explained by the presence of blistered iron; but when alone it cannot pass to the foreign bodies. I hope that the examination of these state of steel any more than to white cast-iron-at calorific capabilities, together with a very simple mode of least, by means of the short reactions which can be assay, may furnish a practical process for determining

effected in metallurgy. This almost absolute impos- the nature and origin of the irons contained in all the sibility of reverting to the state of ferrosum, except, products; their use and value may thus be ascertained. indeed, with great difficulty and in a very unstable it is, moreover, very desirable that there should be a manner, after having existed in the ore in the state of process for testing the qualities to prevent not only inferricum, corresponds, moreover, to the difficulties in the tentional fraud, but also those mistakes which may be way of the chemical reduction of peroxide.

committed in the present state of metallurgy. Its physical characteristic is the malleability which it Verifications of the new principles which I have laid loses only on attaining its ultimate form-blistered iron. down are to be found in the explanation of even the

Its chemical properties canse it to be classed among most obscure phenomena ; a series of verifications which the bodies which combine with at least three atoms of I will succinctly indicate, after having made known the oxygen, and more of an odd number.

laws regulating the action of heat and of reagents in Black and grey cast-irons are not physical conditions the metallurgy of iron. determined by a collection of identical molecules. They are simply ferricum, preserving a part of its properties, PROCEEDINGS OF SOCIETIES. and depositing when slowly cooled the carbon with which the reaction had charged it while hos. In grey

COLLEGE OF PHYSICIANS. cast-iron ferricum is generally predominant; in mottled On Animal Chemistry.A course of Six Lectures by cast-iron the two irons are present with their character- WILLIAM ODLING, M.B., F.R.S., F.R.C.P. istics; ferrosum gives the white portions and the carbon

Friday, May 12, 1865. combined; ferricum gives the grey portions with a car

LECTURE 6. bon deposit. Malleable irons are formed of mixtures in varying

Uric acid. Its excretion throughout the animal kingdom proportions of two irons of different origin, both in the

History of its chemical examination - Its undecomposistate of ferricum. Ferrosum in this state always

bility save by oxidation- Classification of uric acid products

into an-ureides, mon-urcides, and di-ureides- Also into partially preserves its hardness and power of returning carbonic, oxalic, and mesoxalic compounds-Oxidation of to its original form, as I have already described. The

mesozalic into oxalic, and of oxalic into carbonic acid variety found in the irons of commerce depends on the Ureides formed by an elimination of either one or two number of mixtures possible.

atoms of water— Table of uric acid products - Additional The magnetic oxide ores contain the two irons in intermediate and amidated bodies-Oxalic mon-ureides and atomic proportions. These ores give the most stable di-ureides-Mesoxalicmon-ureides associated with barbituric and perfect steels; hence it may be concluded that acid-Mesozalic di-ureides, including hypoxanthine, xanstee is produced by the reunion of two conditions of thine, and uric acid-Their mutual convertibility-Relairon, and that it is nearest perfection when it holds the

tionship of xanthine to guanine— The pseudo-uric and two irons in a closer relation than that which exists in

urozanic acids-Uric acid viewed simply as a compound

of carbonic oxide and urea- - Tissue metamorphosis affected It is not necessary to consider steel as a new state, for magnetic oxide is formed merely of a combi.

by alterative medicines - Activity of loosely combined nation of two oxides.

oxygen-Nitric oxide as a carrier of active oxygen -ComThe correctness of this definition of steel may be

parison between nitric oxide and iodine as oxygenants

Resemblances and differences between iodine and chlorine proved by a very easy experiment: a mixture of soft or

- Free chlorine more active than iodine, and free iodine blistered iron (ferricum) and white cast-iron (ferrosum) more mobile than chlorine- Alterative action of iodine operated on before or after fusioni, always gires when in dependent on ils chemical mobility-Similar characters right proportions a more or less perfect steel recognisable of arsenic, mercury, gc.-Effect of alkalies on tissueby tempering


the ores.

[ocr errors]

CHEMICAL News, 198 College of Physicians.

. Of all the incompletely oxidised products of tissue-meta- tively simple molecules ; that hippuric acid, for instance, morphosis, uric acid is, I suppose, the most important, is constituted of the residues of benzoic acid and glycocine, whether regarded from a physiological and pathological, while tyrosine is constituted of the residues of salicic acid or from a purely chemical point of view. In combination, and ethylamine,—the glycocine and ethylamine themselves chiefly with ammonia, it forms the principal urinary con containing residues of ammonia and of glycolic acid and stituent voided by insects, land reptiles, and birds. alcohol respectively. Now, uric acid is evidently built up Normally, it occurs but in small proportion in the urine in a similar manner, and contains the residues of several of man, while it is found in yet smaller proportion in that constituent molecules. But a hitherto insuperable diffi. of carnivorous, and can scarcely be said to exist–if, culty in determining its exact mode of construction arises indeed, it does habitually exist–in that of herbiverous and from the circumstance of its never having been decomomniverous quadrupeds. According to various autho- posed into the actual molecules of which its constituent sities, it is to be found constantly in the juices of the human residues are the representatives, but only into the oxidised, spleen, liver, lungs, and brain. The merest traces of it or, rather, dehydrogenised, products of these molecules. are also met with normally in blood, but its proportion Add to uric acid an atom of oxygen, so as to burn off two therein under certain forms of disease, such as albuminuria, of its atoms of hydrogen, and it breaks up with the greatest and more especially in gout, becomes very appreciable. ease, though without this additional oxygen it has hitherto In certain cases of gout, indeed, all the fluids of the body proved undecomposible. You will observe from its are more or less saturated with uric acid, and some of formula, CN,H,O,, that uric acid contains five atoms of them even supersaturated, so as to deposit those well-carbon and four atoms of nitrogen, while urea, CN,1,0, known concretions of urate of sodium, commonly called contains only one atom of carbon and two atoms of nitrogen. chalkstones. I need scarcely refer also to the frequent Accordingly, we find that when dehydrogenised uric excess of uric acid discharged from the human kidneys, acid undergoes complete decomposition by an absorption under greater or less derangements of bodily health, and of water, it breaks up into two molecules of urea (conto its deposition in the form of urinary sediment, gravel, taining C,N.) and one molecule of a non-nitrogenous or calculus. As shown by its formula, CNH,O3, uric 3-carbon acid. Whether, however, the residues of these acid consists of only sixteen elementary atoms, and is con- two molecules of urea, obtainable by the oxidation or sequently, as regards its ultimate composition, a far more dehydrogenation of uric acid, pre-exist in uric acid, the simple body than many of those we have previously con- 3-carbon acid alone being the dehydrogenised product, or sidered. Nevertheless, the problem of its intimate consti- whether the residue of the resulting 3-carbon acid pretution for a long time baffled all attempts at solution, and exists in uric acid, the two atoms of urea being produced cannot, even at the present day, be considered as quite by dehydrogenation, there is no evidence to show. The satisfactorily unravelled.

great stability of uric acid under treatment with even Uric acid was discovered in 1776 by the renowned strong acids and alkalies is certainly opposed to its conSwedish chemist, Scheele; but it was first submitted to taining pre-formed residues of urea, since in all undoubtedly a minute investigation by Liebig and Wöhler, whose so constituted bodies the residues of urea are removeable efforts resulted in the production and identification or decomposible with the greatest facility. On the other among other new bodies of alloxantine, alloxanic acid, hand, the assumption of pre-existent urea-residues in uric dialuric acid, uramile, mesoxalic acid, allantoine, myco acid very greatly facilitates our conception of its decommelic acid, parabanic acid, &c., and whose admirable positions, and, receiving the general consent of chemists, work, published in 1838, forms the broad and sound may, I think, be provisionally admitted by us on the prebasis of all our subsequent knowledge. These chemists sent occasion. Be this as it may, when uric acid is subhad been preceded by Brugnatelli and Prout,—the jected to an oxidising agent in presence of water, it gives discoverers of alloxan 'and murexide respectively—and up two of its atoms of hydrogen to the oxidising agent, were succeeded more particularly by Schlieper, Pelouze, while the dehydrogenised product reacts with water to Fritzsche, Gregory, and Illasiwetz. To the number of form mesoxalic acid and urea. Employing chlorine as the bodies already described, Schlieper added the leucoturic, oxidising agent, we have the following reaction :allituric, dilituric, hydantoic, hydurilic, and allanturic or

Uric acid. Water. Chlorine. Mesoxalic. Uroa. Chlorhydric. lantanuric acids, -the last also discovered by Pelouze. In CN 4,03+41,0 + Cl = C,H,05+2CN,1,0 + 2HCl; 1853, Gerhardt, in his celebrated “ Traité de Chemie,' gave a very complete account of the then known uric acid or, supposing the reaction with water to take place after products, and, by dividing them into two well-defined the removal of the hydrogen by chlorine,natural groups, simplified very greatly the knowledge of Dehyd-uric? Water. Mesoxalic. Urea, their origins and metamorphoses. Among subsequent CgN,H,O, + 4H20 C,H,O, + 2CN,H,O. workers, Baeyer has increased the list of compounds by his In the above equations I hare represented both atoms of discovery of pseudo-uric acid, hydantoine, violantine, and urea to be simultaneously separated from the mesozalic the violuric and barbituric acids, the last-named being a

acid ; but in reality their separation is usually effected at body of very great interest, and has also thrown consider. able light upon the nature of the compounds previously

two successive stages, thus :discovered by Schlieper. Moreover, adopting Gerhardt's

Dehyd-uric! Water. Alloxan, classification as a basis, and viewing both old and new CN,H,O, + 2H2O CN,H,O, + CN,H,O. products from the extreme height of modern doctrine, he has published by far the most complete and connected


Mosoxalic. Urea account of the uric acid group of compounds which has CN,H,O, + 2H,0 C,H,O3 + CN,H,O. hitherto been given to the world. The scheme which I

We have, you perceive, three mesoxalic compounds, am about to bring under your notice, and which is, I think first the non-nitrogenous acid, then the compound of the I may say, even more comprehensive, does not differ greatly acid with one atom of urea minus 2H,O, and lastly, the from that of Baeyer in general conception, and is indebted compound of the acid with two atoms of urea minus 41,0, very largely to him for its elaboration. I propose, how-thus :ever, to differ from him in disregarding altogether the molecular arrangement of the different compounds, pre

Mesoxalic. Alloxan. Dehyd-uric? ferring to limit myself in this, as in previous lectures,

C,H,O, CN,2,0 C,N,H,O, simply to questions of origin and relationship.

Now, by hydrogenising mesoxalic acid, we obtain tar.. I have already told you that the great majority of com- tronic acid, C,H,Os, and by hydrogenising alloxan we plex organic bodies are built up of the residues of compara- | obtain dialuric acid, CN,H,O,, which two bodies accord




, } Oct. 27, 1865. College of Physicians.

199 ingly bear to uric acid the same relation that mesoxalic be almost unmanageable, and a very slight agitation would acid and alloxan bear to dehyd-uric acid, thus :

cause the liquid contents to froth over the beaker, but now
Uric Acid.

that the action is a little moderated I may prove to you C,H,O, CAN,1,04 C;N,H,03; the naiure of the gas evolved by pouring some of it on to and, just as our hypothetical dehyd-uric acid yields a lighted taper, which you see is immediately extinguished, mesoxalic acid and alloxan, so should actual uric acid and by pouring some more of it on this clear lime-water, yield tartronic acid and dialuric acid.

which" by agitation therewith is immediately converted In reality, however, these bodies have not been obtained into an opaque mixture of chalk and water. Accordingly, by the mere breaking up of uric acid, but only by rehydro- when uric acid is subjected to a more powerful oxidation genising the mesoxalic acid and alloxan which result from than suffices to produce oxalic acid, we obtain carbonic the breaking up of dehydrogenised uric acid. Despite, acid, which like the oxalic and mesoxalic acids is also however, this flaw in the demonstration, we may pro- capable of colligation with urea. No ureide of carbonic visionally, as I have said, regard the dialuric and aric acid, indeed, has yet been obtained directly from uric acid, acids as tartron-ureide and tartron-diureide respectively. the active treatment which effects the complete oxidation

The several bodies I have just mentioned are typical of of the uric acid effecting also a separation from one three well-defined classes of compounds, to one or other another of the resulting carbonic acid and urea, which, of which the immense number of uric acid products are, however, may be obtained in combination by other means. with but very few exceptions, assignable. We have first Allophanic acid, for instance, is a well known artificial the class of simple non-nitrogenous acids, or an-ureides, mon-ureide of carbonic acid, but so far as I am aware no like the tartronic and mesoxalic acids. Then we have the di-ureide of the acid has been hitherto produced by any class of bodies containing a residue of the acid plus one process whatsoever. residue of urea, or the mon-ureides, such as dialuric acid The mon-ureide of mesoxalic acid, of which I have and alloxan; and lastly, we have the class of bodies con- already spoken-namely, alloxan, is formed from mesoxataining a residue of the acid plus two residues of urea, or

late of urea by an elimination of two atoms of water; but the di-ureides, such as uric acid itself. Confining our there is another ureide-namely, alloxanic acid, which present attention to the an ·ureides, let us consider briefly differs from the original salt by the loss of only one atom their derivation and mutual relationship. Mesoxalic acid, of water. Similarly oxalic acid forms two mon-ureidesthen, the most complex non-nitrogenous produet obtain namely, parabanic acid or paraban analogous to alloxan, able directly from uric acid, constitutes the third term in and oxaluric analogous to alloxanic acid. Carbonic acid, the following series :

however, forms but a single ureide, which is produced by An-ureides.

the elimination of only one atom of water, and accord Carbonic.

ingly belongs to the same series as the oxaluric and alloxC,H,O, Oxalic.

anic acids, thus : C2H20; Mesoxalic.


Ureides. Oxalic acid, you observe, differs in composition from car.

C 4,0, Carbonic CN,1,0, Allophanic.

C bonic acid by one atom of carbonic oxide, Co, in excess ; while mesoxalic acid differs in composition from oxalic

C,H,O, Oxalic

į CN,H,O, Oxaluric. acid by a further atom of carbonic oxide, CO, in excess.

CẢNH0 Paraban. Now, when mesoxalic acid is acted upon by nascent C,2,0, Mesoxalic { CN,H,OAlloxan.

CN,H,O, Alloxanic. oxygen, 0, its excess of carbonic oxide, co, is removed in the form of carb-anhydride, CO2, so as to leave oxalic Similarly among the di-ureides, some are formed from acid, thus :

their corresponding mon-ureides by an elimination of one Mesoxalic. Oxygen. Carb-anhyd. Oxalic.

atom, and others by an elimination of two atoms of water. C,H,O, + 0 CO + C,H,O,

Now, mesoxalic acid is convertible by deoxidation or Hence when uric acid is subjected to a more active oxida- hydrogenation into tartronic acid, as I have already tion than suffices to produce mesoxalic acid, we obtain observed; and by pushing the deoxidation a stage further oxalic acid, which may occur in its simple an-ureide state,

we obtain malonic acid, both of them capable of forming or congregated with one atom of urea to form a mon-ureide mon-ureides and di-ureides ; and in a similar manner the such as parabanic acid, or congregated with two atoms of oxalic and carbonic acids furnish a variety of similarly urea to form a diureide, such as mycomelic acid, a body behaving deoxidation products. When we consider, then, having exactly the same relation to oxalic acid that uric the total number of carbonic or 1-carbon, of oxalic or has to mesoxalic acid.

2-carbon, and of mesoxalic or 3-carbon, hydrogenised Now, just as we can convert mesoxalic into oxalic acid products; and that the majority of these products, like by burning off its excess of carbonic oxide, so may we

their original acids, are capable of forming mon-ureides convert oxalic acid itself into carbonic acid by a precisely by an elimination of one atom, and other mon-ureides by similar oxidation, thus :

an elimination of two atoms of water ; and, further, that Oxalic. Oxygen. Carb-anhyd. Carbonic.

many of these mon-ureides are capable of forming di-ureides C,H,O, + 6 CO, + CH,03.

by a further elimination of one atom and other di-ureides

by a further eliinination of two atoms of water, we are no The rapidity with which the oxidation of oxalic acid can longer surprised at the great number and variety of known take place is easily capable of experimental illustration. In compounds belonging to the uric acid group, and shall this tall beaker, for instance, I will place some ordinary black not be surprised at the dis overy of very many more. oxide or peroxide of manganese MnO2, a compound which The most important of those already known are inreadily parts with one of its two atoms of oxygen to become cluded in the following table. It is divided perpendicuconverted into protoxide of manganese MnO; while in the larly into three columns of an-ureides, mon-ureides, and Alask I will place an ounce or so of commercial oxalic acid. di-ureides ; and perpendicularly into three layers of Now, upon drenching the acid with hot water and pour- carbonic, oxalic, and mesoxalic products. The coming the mixture of solution and crystals upon the oxide pounds connected by means of dotied lines differ in comof manganese, we get, you perceive, a most rapid oxida position from one another by an excess or deficit of one tion of the oxalic acid, accompanied by a violent efferves. atom of urea minus one atom of water ; while those

of carb-anhydride which we shall be able to recog: standing on the same level in the adjoining columns and nise in a minute or two by its high specific gravity and unconnected by dotted lines, differ from one another by by its power of extinguishing flame and of rendering lime- an excess or deficit of one atom of urea minus two atoms water turbid. The effervescence is at first so great as to l of water.


[ocr errors]


CH, Methylic
CHÁO, Carbonic

CAN,I1,0 Methyl-urea
C,N,1,0, Allophanic




.C,N,H60, Acet-urea
.CZN,H,O, Hydantoic

CN, 4.0, Glycoluril

CNHO3 Allantoine
C,H,O, Acetic
Сно, Glycolic

CN,H,O, Hydantoine-
CHO Glyoxylic
.CZN, 1,03 Allanturic

CN.4,0, Mycomelic bag
CONHO Oxaluric

CzN,H,O, Parabanic

CNHO Hypoxanthine
C,H,, Malonic
CN,1,0, Barbituric

CNH0, Xanthine
Сно. Tartronic
CNHO Dialuric.

CON HO; Uric acid
CNHOS Alloxanic

CAN,H,O, Pseudo-uric
C,H,O Mesoxalic

CN,H,O, Alloxan Even this table, however, is far from being complete. Mycomelic acid may be obtained among other processes Thus, I have introduced only one alcoholic urea as a type by treating uric acid with water under pressure, thus :-namely, the methylic, excluding its homologues. I have Uric acid.

Mycomelic acid, Carbonic oxido. also omitted uroxanic acid and several amidated and nitro- CN,H,O,


CO. compounds, to which I shall presently refer. Moreover, between some of the consecutive mon-ureides shown in the exactly the same relation that uric acid stands to alloxan.

As I have before observed, it stands to paraban in table there exist certain diameric bodies formed by the From the observations of Hlasiwetz it seems probabie union of the two consecutive mon-ureides with elimination that some supposed urate of ammonia deposits occurring of water. Thus, allituric acid is a diamerone of hydan- in urine really consist of mycomelic acid, which similarly toine and allanturic acid, while leucoturic acid is a dia- evolves ammonia when treated with alkalies, and yields merone of allanturic acid and oxaluric or parabanic acid, murexide when evaporated with nitric acid. thus:

Of mesoxalic mon-ureides, alloxan and barbituric acid Allituric. Water. Hydantoine. Allanturic. C.N.1604 + H2O CN,H,O, + C2N,H,O3.

seem to be the most important. Alloxan, the first dis

covered product of the artificial oxidation of uric acid, has Leucoturic. Water. Allanturic. Parabanic. CNHO + HẠO H,0 - C,N,H,O, + CAN,H,O.

recently been recognised by Liebig as a pre-formed con

stituent of urine. By treatment with bromine, it yields In a precisely similar manner, among mesoxalic com- bibromobarbituric acid, which is successively convertible pounds we have hydurilic acid, a diamerone of barbituric by hydrogenation into the bromobarbituric and barbituric acid and dialuric acid; while alloxantine is a diamerone of acids, which last serves as a sort of nucleus in the followdialuric acid, and alloxanic acid or alloxan, thus :

ing series of compounds :Hydurilic. Barbituric. Dialuric.

Mesoxalic Mon-ureides.' CAN,HOG + 1,0 = CqN,H,O, t C,N,H.04.

CN,H (HO),0, Alloxanic. Alloxantine. Water.


CN,H,Br2O3 Bibromobarbituric, CN 4,0, + H2O CAN,H,O4 + CN,H,O,


Barbituric. Of the many bodies above formulated, only a few call



CNH (HOẶ0, Dialuric. for any special remark. Hydantoic acid is also known as

Uramile. glycoluric acid, which is, perhaps, a better name for it.

CNH (HAN), Again, the body here called allanturic acid is probably

CNH (HNSO)O, Thionuric.

Violuric. identical with the lantanuric acid of Pelouze, and also with

CNH (NO)02 difluan. Oxaluric acid is interesting from the alleged occur

CNH (NO)O, Dilituric. rence of its calcium salt in human urine, in the form of the

CNH (1,0) Violantine. dumb-bell crystals so often associated with the octahedral The last compound on the list-namely, violantinecrystals of oxalate. That these dumb-bells may consist of seems to be not a diamerone or residuary, but a completed oxalurate of calcium, as suggested by their discoverer, compound of the violuric and dilituric acids. It is Golding Bird, is not indeed improbable ; but the evidence observable that the mutual relationship of barbituric acid, that they really are so constituted is anything but satis- dialuric acid, and uramile in this sub-group is strictly factory. The relations of allanturic and oxaluric acids to parallel to that of allanturic acid, oxaluric acid, and oxal. another uric acid product known as oxaluramide are obvi- uramide in the preceding one. Moreover, the malonic and ously those of hydrogen and water to ammonia, as illus- barbituric acids are homologous with the oxalic and paratrated in the case of so many other compounds, thus :- banic acids respectively, or the most oxidised of known H.H Hydrogen CN, H,HO, Allanturic.

2-carbon uric acid products are homologically the repreH.HO Water CN, H (HO)O, Oxaluric.

sentatives of the least oxidised 3-carbon products, thus -H.H,N Ammonia C3N,H,(H2N)O, Oxaluramide.

C,H,O, Oxalic CAN,H,O, Parabanic Allantoine, as shown by the fine specimen lent me by

CH0 Malonic CNHO, Barbituric, Messrs. Hopkins and Williams, is a beautiful crystalline although from another point of view they correspond more body existing in the allantoic fluid of the fætal and in the urine nearly with mesoxalic acid and alloxan, as I have already of the sucking calf. It has also been noticed by Frerichs remarked. and Städeler in the urine of two dogs, upon whose lungs The relationship subsisting between the three mesosal. they had been experimenting, and is very easily procurable diureides, though long suspected from the similarity of their from uric acid by oxidation with peroxide of lead. By formulæ-hypoxanthine CN, 1,0, xanthine C N 1,0, deoxidation, it yields glycoluril (Rheineck).

and uric acid c:N 4,0,-has but very recently received an






Oct. 27, 1865.

College of Physicians.





experimental demonstration at the hands of Strecker and


Parabanic. Rheineck. With the first of these bodies, or hypoxanthine,

C,N,H,(HO)2 + H2O + O2 = C,N,H,O +

Úrea. originally found by Scheerer in human and bovine splenic juices, the sarcine, subsequently discovered by Strecker in

CNH (HO) + CO, Guanine.

Para banic. juice of flesh, and thought to be a distinct base, has since

C, H,(H,N)0+H,0 + 0,=C,N,H,O, + proved to be identical. From the results of Scheerer,

Guanidine. Strecker, Gorup-Besanez, and others, it appears that

CN,H,(HAN) + CO2. hypoxanthine exists to a very appreciable extent in most Moreover, xanthine itself occurs in small quantity as a glandular juices and in muscular tissue, particularly of secondary product of the above oxidation of guanine, and the heart, while it has also been recognised in brain sub-probably might be obtained in larger quantity by treating stance and in the blood and urine. It occurs as a white guanine with nitrous acid, according to the general method crystalline powder, insoluble in cold and sparingly soluble adopted for converting amidated into hydrated bodies, in' hot water. By oxidation with nitric acid, it yields thus :xanthine, and hence gives the characteristic nitric acid re

Guanine. action of xanthine, which compound has also been detected CN,H,(H,N)O +(HO)NO = CĂN H (HO)O + N2 +H,0? in blood and in most animal juices. Under the name of xanthic oxide, it was discovered in 1819 by the elder

That the guanine extracted from guano is a constituent Marcet in a variety of urinary calculus, which subsequent of the birds' excrement as voided, and not a product of experience has proved to be very rare. It has been met decomposition, is rendered probable by its occurrence with more frequently, indeed, though still very seldom, under other circumstances. Thus it forms the chief as an amorphous urinary deposit, and in one case recorded portion of the excrement of the garden spider, has been by Bence Jones it occured in lozenge-shaped crystals. recognised by Scheerer in the pancreas of the horse, and is Its habitual presence, however, in small quantity as a

occasionally met with in human urine. dissolved constituent of urine seems now to be very well

We have now only left for consideration the pseudoestablished. Xanthine, moreover, is not only known as a

uric and uroxanic acids, which we may regard as terms urinary, but also as an intestinal concretion, for Göbel has in the following series :met with it as the chief constituent of certain oriental

C:N H, 02

Uric. bezoar stones obtained from ruminating animals. I have

CN H,02+ H,O=CN H. oPseudo-uric. already referred to Strecker's artificial production of CON H2O3 + 2H2O=CN H. Og

Unknown. xanthine by the oxidation of hypoxanthine or sarcine with C N H 03+34,0 - CN HO. Uroxanic. nitric acid. Conversely, Strecker and Rheineck have very CN H 0,+41,0 = CH 0, Tartronic + 2CN,H,0 Urea, recently shown that uric acid by deoxidation with sodium- . amalgam yields a mixture of xanthine and hypoxanthine,

Pseudo-uric acid is a recent discovery of Baeyer's. It i the latter in greatest proportion, so that the actual rela? has not actually been produced by the direct or indirect

tionship of these three bodies is now placed beyond all hydration of uric acid, but only by the combination of question. Hitherto, hypoxanthine and xanthine, having acid converts ammonia into anomalous cyanate of am

cyanic acid vapour with uramile. Just, in fact, as cyanic Þeen obtained in small quantities only, have not been monia or urea, so does it convert the residue of ammonia subjected to any detailed examination. It can scarcely contained in uramile into a residue of urea, so as to change be doubted, however, that xanthine is a mon-ureide of the amido-monureide into a simple diureide, thus :barbituric and a di-ureide of malonic acid, in the same sense that uric acid is a mon-ureide of dialuric and

Uramile. Cyanic acid. a di-ureide of tartronic acid. We may hope, indeed, to

CN,H,(NH,)0, +CNHO=CN, H,(CN,H,0)0,

Pseudo-uric, have these relations very soon established by experi

CAN H,O, ment; for even if it should not prove possible to prepare xanthine advantageously from uric acid, still the fact of Pseudo-uric acid occurs as a white crystalline almost its close relationship therewith would lead us to expect insoluble powder. Hitherto it has not proved dehydrateits more abundant existence than has been hitherto able into uric acid ; but by dehydrogenisation in presence imagined; particularly, for instance, in the excreta of of water it behaves like uric acid, breaking up into alloxan those animals whose normal mode of tissue waste results and urea. The compound CN, H,0, is unknown, while in the production of uric acid rather than urea. This uroxanic acid, C.N.1,006, is known but very imperfectly. expectation is strengthened by the extraction from that Unlike pseudo-uric acid, it really results from the absorpvaluable dried excrement of sea-fowl known as guano of tion of water by uric acid, and is produced in the form of A feeble base called guanine, which bears to xanthine the its potassium salt by boiling uric acid for a long time in same often-referred to relation that ammonia bears to solution of caustic potash. In the free state it occurs as water, as shown in the following series of formulæ :- a white, glistening, sparingly soluble powder. The absorpC.N.1,0.


tion of a fourth atom of water by uric acid would proCN H (NO)


bably lead, not to the formation of a new hydrate, CNH, H,NO


but to the breaking up of the uric acid itself, possibly CNH (HO)20

Uric acid.

into tartronic and urea. Just, in fact, as uric acid, and doubtless xanthine, yields products, by no means all that are known, and I have

I hare already referred to upwards of forty uric acid by oxidation parabanic acid and urea, so does guanine indicated the existence of many more, as yet unknown, to yield by oxidation parabanic acid and amido-urea or fill up gaps in the different series. Now, when we reflect guanidine,* thus :

that in all probability most of these compounds, actual By the oxidation of kreatine, which has been already described and problematical, do not stand alone, but are associated as a polymerone of glycolic acid, methylamine, and uren, its glycolic each with a more or less numerous set of isomers,—that is residue is converted into oxalic acid, while its methylamine and urea residues are left in combination to form methylamido-urea or methyl but a different molecular arrangement-we scarcely venture

to say, of bodies having the same ultimate composition, uramide, & compound homologous with amido-urea or guanidine, thus:

to contemplate the almost overwhelming intricacy with CN, 113(HO)


which we are threatened. To us, as physicians, however, CN, H311N).


the subject is capable of assuming a simpler aspect. On Methyluramine.

any view of its constitution, hydrated uric acid differs in Again, bluret C2N3H502, or C2N2H3(H2N)02, may be regarded as carbo-guanidinic acid, just as allophan C,N28.03 or C2N2H:3 (110)0, composition from two atoms of urea by the addition of is regarded as carb-ureie acid,

three atoms of carbonic oxide, capable of oxidation into

[ocr errors]
[ocr errors]
« PoprzedniaDalej »