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LECTURES ON ORGANIC CHEMISTRY:
NOVEMBER 30, 1844. separated and replaced by hydrogen; fulmini acid, upon its separation from its salts by means of another acid decomposes, and its elements distribute themselves among th, constituents of the acid, by means of which the decompositiol nates cannot be
LECTURES ON
ORGANIC CHEMISTRY:
was
effected.
Cyanic acid, upon coming into contact with water, decom poses immediately into carbonic acid and ammonia; this aci( University of Giessen. likewise, therefore, cannot be produced from its salts in an isolate< bears a temperature of 300° withou BY JUSTUS LIEBIG, M.D., PH. D., F.R.S., M.R.I.A. state. Cyanurate of silver whilst cyanate of silver, exposed t< undergoing decomposition, Professor of Chemistry in the University of Giessen. the same temperature, decomposes, with ignition and evolution o: carbonic acid and nitrogen gas, in the proportion of two to one CYANOGEN AND ITS COMPOUNDS CONTINUED-CYANURIC ACIDleaving semicyanide (subcyanide) of silver behind. CHLORIDE OF CYANOGEN. Fulminate of silver, exposed to the same temperature, decom. GENTLEMEN,—Itold you, in my last lecture, that cyanuric acid poses with ignition and detonation, evolving, likewise, carboni, is an isomeric modification of cyanic acid. I have now to enter, acid and nitrogen in the proportion of two to one, and leaving somewhat more minutely, upon the consideration of its constitu- semicyanide of silver behind. It is obvious that the elements o] tion and properties. The crystals of cyanuric acid contain a these three, in other respects, analogously-constituted compounds certain amount of water of crystallization-viz., four atoms of are maintained respectively in connexion by a very dissimilai water to the elements of three atoms of hydrated cyanuric acid. force; you see, also, that the difference between the deportmeni of cyanate of silver and that of cyanurate of silver is not more 3 (Cy 0, H 0) z- 4 aq. considerable than the difference between the properties of cyanate The presence of this water of crystallization is quite decisive as of silver and those of fulminate of silver. to the constitution and formula of cyanuric acid. This acid must It is a favourite idea with some chemists, to the decontain. in every single atom, the elements of three atoms of tonating properties of fulminate of silver on theexplain oi assumption cyanic acid; its formula cannot be analogous to that of common certain hypothetical presuppositions as to the manner in which cyanic acid, for, were it so, the following would be the composi- its elements are arranged. Cyanate of silver does not detotion of the hydrated crystallized acidnate by friction, concussion, &c. &c.; how, then, is it to be accounted for, that the analogously-constituted fulminate of Cy O + H O + 11/3 aq. i. e., it would contain a fraction of an atom of water of crys- silver is decomposed with such vehemence by the agency of the tallization, which assumption is inadmissible according to the same causes? Thus, for instance, Berzelius imagines that fulmiWhen freed, however, from this water of nate of silver is a double compound of nitride of silver (Hg N) atomic theory. crystallization—which it loses upon the application of a gentle with the silver salt of a peculiar acid, to which salt he assigns the heat-it contains exactly the same elements as the hydrate of the formula, C, N H Os + Hg 0 ; the detonating property he -common cyanic acid. The properties of cyanuric acid, whether ascribes to the nitride of silver. Now it is very true that many free, or in combination with bases, are exceedingly different from metallic nitrides have the property of decomposing, with exthose of cyanic acid and of fulminic acid; neither of the latter acids plosion, upon being exposed to heat; but to infer the existence of a nitride in fulminate of silver, simply because the latter substance can be isolated from their salts by other acids, without undergoing decomposition, whilst cyanuric acid dissolves in alkalies, and may detonates, can certainly not be considered a very scientific conbe boiled with them and separated from them by acids, without clusion ; on the contrary, it militates against every scientific undergoing the slightest alteration. Cyanuric acid dissolves in principle, since the fact of the detonation would thus compel us to concentrated sulphuric acid, and separates again from this solu- assume as true, two hypotheses—viz., 1. the existence of a nitride of upon the addition of water; but it dissolves likewise in strong silver, which, in reality, does not exist-(the metallic nitrides tion nitric acid, and crystallizes from this solution in long anhydrous which we know to exist contain three equivalents of nitrogen to needles. The force which maintains the elements of cyanuric one equivalent of metal, whilst this supposed nitride of silver acid in mutual connexion is evidently much more powerful than would contain only one equivalent of nitrogen to one equivalent that which connects the same elements in cyanic acid and in of metal;) 2. the existence of an acid in fulminate of silver, fulminic acid, and there is no doubt that this is owing princi- which, although assumed to be of similar composition with pally to a different arrangement of its molecules. The constitution alloxanic acid, cannot be produced therefrom. Metallic nitrides, of the cyanurates affords us some explanation respecting this point. when decomposed by acids, yield ammonia as a product of their Let us designate the composition of cyanuric acid, dried at 212° decomposition; but fulminate of silver, upon its decomposition by acids, yields hydrocyanic acid and not ammonia. (F.) by As I have already observed, the more or less ready decomH 0 3 posibility of any compound depends upon the greater or less 3 Cy Cy 0O + { H O DELIVERED DURING THE WINTER SESSION,
1844,
IN
THE
+H0
force of attraction which maintains in connexion the elements of the compound atom; and the dissimilar effect of the more or less powerful action of this force may be rendered intelligible by assuming the component atoms to exist in a position of greater or lesser proximity to each other, but certainly -not by the mode of their molecular arrangement. It is, however, quite certain that the elements in these three acids are arranged in a very dissimilar manner, and that the difference in their properties is dependent on their dissimilar First potass salt. Second potass salt. Dry cyanuric acid. molecular arrangement. CHO CKO CKO If we consider these acids as oxygen compounds of cyanogen, 3 Cy 0 3 Cy 0 0 0 0 3 Cy 0 the question naturally occurs, Does the cyanogen exist in these no matter in what state of combination or conacids as A mere glance at these formulae shews at once that the first densationcyanogen, ? This question may, I believe, be answered in the potass salt corresponds to the acid phosphate of potass, whilst as far as cyanic and cyanuric acid are concerned, for the second corresponds to the common (neutral) phosphate of affirmative, one of these acids may be readily produced from the other, and potass ; a cyanurate of potass, with three atoms of potass, has vice versli. Cyanic acid may be converted into cyanuric acid, andhitherto not yet been produced, but there exist two cyanurates of acid into cyanic acid. silver, the one of which contains three atoms of oxide of silver, cyanuric If to a moderately-concentrated solution of cyanate of potass in thus corresponding to phosphate of silver-namely, the tribasic water some acetic acid is added-about one-third of the amount phosphate of silver. which would be necessary to decompose the potass salt-there First cyanurate of silver. Second cyannrate of silver. precipitates, in the course of a few hours, a copious amount of a. white crystalline powder, consisting simply of acid cyanurate of fHgO
According to this formula, we may say that the atom of anhydrous cyanuric acid is formed by the combination of three atoms of anhydrous cyanic acid into one single atom; the three atoms of water of hydration designate exactly its saturating ’, capacity, just, as we have seen, is the case with respect to phos- i phoric acid. We know, indeed, two potass salts of cyanuric acid, having the following composition:-
3 Cy O + (HO {H O 3 Cy O + (HO {H O 3 Cy O + (HO {K O
3 Cy O + {)H 0 Hg 0
CHgO
Hg 0 3 Cy O + {ago
O O Upon looking once more at the properties of cyanic acid, fulminic acid, and cyanuric acid, we find that the last of these three acids alone can exist in contact with water and other acids. Fulminic acid cannot be isolated—i.e.. the metal in the fulmi-
No. 1109.
potass.
- 3 Cy 0 +
g0
{2H0
If you take a small retort, with dry cyanuric acid, connecting the retort, air-tight, with a receiver surrounded by ice, and expose the retort to the action of fire, its contents will completely
274 you will find a colourless fluid of an disappear, and in the receiver extremely pungent odour, like the strongest vinegar: this fluid is hydrated cyanic acid. This is obviously a most remarkable transformation, and the discovery of it afforded us the first, and, indeed, as yet, our only method of isolating cyanic acid, or, at least, its hydrate. The vapour of this acid, brought into contact with forms with it the of
in one volume, three times as much cyanogen and chlorine as thegaseous chloride of cyanogen, so that we may say the former is produced by condensation,-i. e., by a closer approximation of the atoms to each other. Three volumes of the gaseous chloride of cyanogen condense and combine, in order to form one volume of the solid chloride of cyanogen. Now if, from the manner of arrangement and state of conammonia, cyanate ammonia, which, upon application of a gentle heat, is converted into urea; brought into densation in which the cyanogen and chlorine atoms exist in the contact with potass, this acid forms therewith cyanate of potass. solid chloride of cyanogen, we draw our ioferences as to the Accordingly, there exists not the slightest doubt that cyanic chemical constitution of the cyanuric acid formed by the transposiacid may be converted into cyanuric acid, and vice versti. tion of the elements of this solid chloride of cyanogen with the Wherein, then, does the difference between these two acids con- elements of water, it is evident that the cyanogen and oxygen sist ? To enable you to account for this difference, I need only atoms forming cyanuric acid, must be considered to exist in this make you acquainted with the properties of two other cyanogen acid in the same state of condensation as the chlorine and cyanocompounds. There exist two compounds which cyanogen forms gen atoms exist in the solid chloride of cyanogen. This differwith chlorine-the one of these compounds is gaseous at the com- ence in the molecular arrangement and state of condensation of mon temperature, and is converted into a fluid at very low temthe cyanogen and oxygen atoms, forming respectively cyanic acidand cyanuric acid, explains the difference in the properties of peratures, whilst the other is solid at the common temperature. If you saturate strong hydrocyanic acid with chlorine gas, you these two acids, exactly as in the instance of the numerous comobtain a solution of the gaseous chloride of cyanogen in water; binations of carbon with hydrogen, which, though possessing the upon the application of a gentle heat, chloride of cyanogen same per centage composition, exhibit dissimilar properties. The escapes from this solution in the form of gas. If you transmit this relative proportion of the atoms composing their elements is the gas through a tube containing fused chloride of calcium, so as to same, but the number of simple atoms which have combined to free it from moisture, and conduct it then into a vessel surrounded form a compound atom, is dissimilar in the various compounds. by a mixture of snow and common salt-(by which means a very According to this, we may express the constitution of the two high degree of cold is produced)-the gas is converted into a chlorides of cyanogen, and of the two acids ’respectively arising limpid fluid, which may be kept in glass tubes closed by fusion. from the transposition of their elements with the elements of I say, this fluid chloride of cyanogen may be kept, but I must water, as follows :add, that it does not preserve its properties intact, for in summer, 1 atom of gaseous chloride of cyanogen cry Cl when the external temperature is high, and the tendency of the 1 atom of anhydrous cyanic acid ...... cry 0 fluid to change into vapour becomes more powerful, so as to in1 atom of solid chloride of cyanogen... = Cy Cl3 crease the pressure in the small glass tubes, the fluid chloride of 1 atom of anhydrous cyanuric acid ‘ Cy3 Os cyanogen is observed to become gradually converted into white And thus we assume acid to be formed by the cyanuric may solid crystals, which consist simply of the second chlorine comor condensation of the elements of three atoms of pound of cyanogen-viz., the solid chloride of cyanogen, (solid at combination the common temperature.) Both these compounds have the same cyanic acid into one single atom. , The fact that cyanuric acid is more permanent, and less readily composition, as is evident from their analysis. We find in both of them one equivalent of chlorine to one equivalent of cyanogen. decomposed than cyanic acid, seems to militate against the Now if we assume the chlorine replaced by one equivalent ofgeneral rule, according to which, the force of affinity and,attraction which connects the molecular elements is less powerful in oxygen, we have the formula of cyanic acidcomplex than in simple atoms. This is, however, easily exCy + Cl = Chloride of cyanogen plained by the greater state of condensation in which the elements exist in cyanuric acid, and consequently the greater proximity Cy + 0 = Anhydrous cyanic acid. of the atoms to each other. The formation of cyanuric acid from Both chlorides of cyanogen decompose with water, transposing andl cyanic acid, as well as the decomposition of cyanuric acid, finda of with the elements the latter the substance ; combining gaseous explanation in this assumption. Cyanic acid and cyanuric chloride of cyanogen transposes with the elements of water, form- ready acid contain both the same elements, but the former is a simple ing hydrochloric acid and cyanic acid, and since the latter is not atom, whilst the latter is a complex atom. If we mix cyanate of persistent in contact with water, but transposes with the elements: potass with acetic acid, or with a small quantity of a strong-acid, of this body, forming carbonic acid and ammonia, which latter insufficient in amount to effect the complete decomposition of again combines with the hydrochloric acid, forming sal am-_: this salt, part only of the cyanate is decomposed, the decomposing moniac, we obtain by the transposition of the gaseous chloride acid sharing the potass with the cyanic acid, and thus liberating of cyanogen with four equivalents of water, one equivalent of sal a certain amount of cyanic acid; part of this liberated cyanic ammoniac, and two equivalents of carbonic acid. acid transposes with the elements of the water of the menstruum, Chloride of Hydrochloric Water. acid. forming carbonic acid and ammonia, whilst the remainder is acid. Cyanogen. Cyanic absorbed as hydrate by the still undecomposed portion of the Cl H Cy Cl + HO Cy 0 + cyanate of potass, and combining with the elements of this salt, 3 acid H 0 H Cl plus Cyanic plus transforms it into cyanurate of potass. The action of heat causes Carbonic Sal acid. ammoniac. C2 the complex atom of hydrated cyanuric acid to separate into= Cs 04 + Cl H, N H, three simple atoms of hydrated cyanic acid. H Cl to these views, the hydrate of cyanuric acid consists of From this manner decomposition we may infer that the of According one atom of anhydrous cyanuric acid, combined with three gaseous chloride of cyanogen is the compound corresponding to) atoms of water; and thus its constitution is similar to that of cyanic acid, and that these two substances have a similar con- phosphoric acid,-i. e., it is, like the latter, a tribasic acid. The stitution. comparison of the salts formed by phosphoric acid and by Now, if you bring the solid chloride of cyanogen into contactt cyanuric leaves no doubt as to the analogous nature of these with water, and apply heat, its elements transpose likewise with1 two acids.acid, the elements of the water, but instead of forming sal ammoniac PHOSPHATES. and carbonic acid, they form hydrochloric acid and cyanuric acid..................... Phosphoric == P 0;, + 3HO acid. It is obvious that the cyanogen in the gaseous chloride of exists in the same state and manner of combination as (Basic) Phosphate of silver = P O5 + 3 Ag 0 it does in cyanic acid, whilst the cyanogen in the solid chloride 2K0 of (neutral) Phosphate potass... (Neutral) potass = P 0 is contained in the same state and manner of combination as in KO cyanuric acid. We possess a very simple means with volatile = P (Acid) Phosphate of potass 05 + bodies, to ascertain whether the molecular arrangement of two substances of analogous composition differs or not. This means CYANURATES. is the determination of their respective specific weights when in == acid..................... Cyanuric Cyg O3 + 3 H 0 the gaseous state. We are thus enabled to ascertain what num= of silver ... ber of simple atoms their elements contain respectively in equal (Basic) Cyanurate Cys Os + 3 Ag 0 2 K- 0 volumes. The two chlorides of cyanogen are volatile, and admit (Neutral) Cyanurate of potass = Cy3 O3 of being weighed in their gaseous state. By comparing the relative weight of their gases in equal volumes, we are enabled to (Acid) Cyanurate of potass = Cy, determine whether their elements are arranged in a similar or dissimilar manner. Now this mode of determination has shewn The further consideration of this subject we will defer to the that the solid chloride of cyanogen contains, in the gaseous state, next lecture. ...
,
.
t .
í
H,
N Os 0)
-
1
cyanogen
......
...
......
= P 05 + 1 H 0 {KO +H{
...
O O3 + {K O ’
LECTURES ON
ORGANIC CHEMISTRY:
was
effected.
Cyanic acid, upon coming into contact with water, decom poses immediately into carbonic acid and ammonia; this aci( University of Giessen. likewise, therefore, cannot be produced from its salts in an isolate< bears a temperature of 300° withou BY JUSTUS LIEBIG, M.D., PH. D., F.R.S., M.R.I.A. state. Cyanurate of silver whilst cyanate of silver, exposed t< undergoing decomposition, Professor of Chemistry in the University of Giessen. the same temperature, decomposes, with ignition and evolution o: carbonic acid and nitrogen gas, in the proportion of two to one CYANOGEN AND ITS COMPOUNDS CONTINUED-CYANURIC ACIDleaving semicyanide (subcyanide) of silver behind. CHLORIDE OF CYANOGEN. Fulminate of silver, exposed to the same temperature, decom. GENTLEMEN,—Itold you, in my last lecture, that cyanuric acid poses with ignition and detonation, evolving, likewise, carboni, is an isomeric modification of cyanic acid. I have now to enter, acid and nitrogen in the proportion of two to one, and leaving somewhat more minutely, upon the consideration of its constitu- semicyanide of silver behind. It is obvious that the elements o] tion and properties. The crystals of cyanuric acid contain a these three, in other respects, analogously-constituted compounds certain amount of water of crystallization-viz., four atoms of are maintained respectively in connexion by a very dissimilai water to the elements of three atoms of hydrated cyanuric acid. force; you see, also, that the difference between the deportmeni of cyanate of silver and that of cyanurate of silver is not more 3 (Cy 0, H 0) z- 4 aq. considerable than the difference between the properties of cyanate The presence of this water of crystallization is quite decisive as of silver and those of fulminate of silver. to the constitution and formula of cyanuric acid. This acid must It is a favourite idea with some chemists, to the decontain. in every single atom, the elements of three atoms of tonating properties of fulminate of silver on theexplain oi assumption cyanic acid; its formula cannot be analogous to that of common certain hypothetical presuppositions as to the manner in which cyanic acid, for, were it so, the following would be the composi- its elements are arranged. Cyanate of silver does not detotion of the hydrated crystallized acidnate by friction, concussion, &c. &c.; how, then, is it to be accounted for, that the analogously-constituted fulminate of Cy O + H O + 11/3 aq. i. e., it would contain a fraction of an atom of water of crys- silver is decomposed with such vehemence by the agency of the tallization, which assumption is inadmissible according to the same causes? Thus, for instance, Berzelius imagines that fulmiWhen freed, however, from this water of nate of silver is a double compound of nitride of silver (Hg N) atomic theory. crystallization—which it loses upon the application of a gentle with the silver salt of a peculiar acid, to which salt he assigns the heat-it contains exactly the same elements as the hydrate of the formula, C, N H Os + Hg 0 ; the detonating property he -common cyanic acid. The properties of cyanuric acid, whether ascribes to the nitride of silver. Now it is very true that many free, or in combination with bases, are exceedingly different from metallic nitrides have the property of decomposing, with exthose of cyanic acid and of fulminic acid; neither of the latter acids plosion, upon being exposed to heat; but to infer the existence of a nitride in fulminate of silver, simply because the latter substance can be isolated from their salts by other acids, without undergoing decomposition, whilst cyanuric acid dissolves in alkalies, and may detonates, can certainly not be considered a very scientific conbe boiled with them and separated from them by acids, without clusion ; on the contrary, it militates against every scientific undergoing the slightest alteration. Cyanuric acid dissolves in principle, since the fact of the detonation would thus compel us to concentrated sulphuric acid, and separates again from this solu- assume as true, two hypotheses—viz., 1. the existence of a nitride of upon the addition of water; but it dissolves likewise in strong silver, which, in reality, does not exist-(the metallic nitrides tion nitric acid, and crystallizes from this solution in long anhydrous which we know to exist contain three equivalents of nitrogen to needles. The force which maintains the elements of cyanuric one equivalent of metal, whilst this supposed nitride of silver acid in mutual connexion is evidently much more powerful than would contain only one equivalent of nitrogen to one equivalent that which connects the same elements in cyanic acid and in of metal;) 2. the existence of an acid in fulminate of silver, fulminic acid, and there is no doubt that this is owing princi- which, although assumed to be of similar composition with pally to a different arrangement of its molecules. The constitution alloxanic acid, cannot be produced therefrom. Metallic nitrides, of the cyanurates affords us some explanation respecting this point. when decomposed by acids, yield ammonia as a product of their Let us designate the composition of cyanuric acid, dried at 212° decomposition; but fulminate of silver, upon its decomposition by acids, yields hydrocyanic acid and not ammonia. (F.) by As I have already observed, the more or less ready decomH 0 3 posibility of any compound depends upon the greater or less 3 Cy Cy 0O + { H O DELIVERED DURING THE WINTER SESSION,
1844,
IN
THE
+H0
force of attraction which maintains in connexion the elements of the compound atom; and the dissimilar effect of the more or less powerful action of this force may be rendered intelligible by assuming the component atoms to exist in a position of greater or lesser proximity to each other, but certainly -not by the mode of their molecular arrangement. It is, however, quite certain that the elements in these three acids are arranged in a very dissimilar manner, and that the difference in their properties is dependent on their dissimilar First potass salt. Second potass salt. Dry cyanuric acid. molecular arrangement. CHO CKO CKO If we consider these acids as oxygen compounds of cyanogen, 3 Cy 0 3 Cy 0 0 0 0 3 Cy 0 the question naturally occurs, Does the cyanogen exist in these no matter in what state of combination or conacids as A mere glance at these formulae shews at once that the first densationcyanogen, ? This question may, I believe, be answered in the potass salt corresponds to the acid phosphate of potass, whilst as far as cyanic and cyanuric acid are concerned, for the second corresponds to the common (neutral) phosphate of affirmative, one of these acids may be readily produced from the other, and potass ; a cyanurate of potass, with three atoms of potass, has vice versli. Cyanic acid may be converted into cyanuric acid, andhitherto not yet been produced, but there exist two cyanurates of acid into cyanic acid. silver, the one of which contains three atoms of oxide of silver, cyanuric If to a moderately-concentrated solution of cyanate of potass in thus corresponding to phosphate of silver-namely, the tribasic water some acetic acid is added-about one-third of the amount phosphate of silver. which would be necessary to decompose the potass salt-there First cyanurate of silver. Second cyannrate of silver. precipitates, in the course of a few hours, a copious amount of a. white crystalline powder, consisting simply of acid cyanurate of fHgO
According to this formula, we may say that the atom of anhydrous cyanuric acid is formed by the combination of three atoms of anhydrous cyanic acid into one single atom; the three atoms of water of hydration designate exactly its saturating ’, capacity, just, as we have seen, is the case with respect to phos- i phoric acid. We know, indeed, two potass salts of cyanuric acid, having the following composition:-
3 Cy O + (HO {H O 3 Cy O + (HO {H O 3 Cy O + (HO {K O
3 Cy O + {)H 0 Hg 0
CHgO
Hg 0 3 Cy O + {ago
O O Upon looking once more at the properties of cyanic acid, fulminic acid, and cyanuric acid, we find that the last of these three acids alone can exist in contact with water and other acids. Fulminic acid cannot be isolated—i.e.. the metal in the fulmi-
No. 1109.
potass.
- 3 Cy 0 +
g0
{2H0
If you take a small retort, with dry cyanuric acid, connecting the retort, air-tight, with a receiver surrounded by ice, and expose the retort to the action of fire, its contents will completely
274 you will find a colourless fluid of an disappear, and in the receiver extremely pungent odour, like the strongest vinegar: this fluid is hydrated cyanic acid. This is obviously a most remarkable transformation, and the discovery of it afforded us the first, and, indeed, as yet, our only method of isolating cyanic acid, or, at least, its hydrate. The vapour of this acid, brought into contact with forms with it the of
in one volume, three times as much cyanogen and chlorine as thegaseous chloride of cyanogen, so that we may say the former is produced by condensation,-i. e., by a closer approximation of the atoms to each other. Three volumes of the gaseous chloride of cyanogen condense and combine, in order to form one volume of the solid chloride of cyanogen. Now if, from the manner of arrangement and state of conammonia, cyanate ammonia, which, upon application of a gentle heat, is converted into urea; brought into densation in which the cyanogen and chlorine atoms exist in the contact with potass, this acid forms therewith cyanate of potass. solid chloride of cyanogen, we draw our ioferences as to the Accordingly, there exists not the slightest doubt that cyanic chemical constitution of the cyanuric acid formed by the transposiacid may be converted into cyanuric acid, and vice versti. tion of the elements of this solid chloride of cyanogen with the Wherein, then, does the difference between these two acids con- elements of water, it is evident that the cyanogen and oxygen sist ? To enable you to account for this difference, I need only atoms forming cyanuric acid, must be considered to exist in this make you acquainted with the properties of two other cyanogen acid in the same state of condensation as the chlorine and cyanocompounds. There exist two compounds which cyanogen forms gen atoms exist in the solid chloride of cyanogen. This differwith chlorine-the one of these compounds is gaseous at the com- ence in the molecular arrangement and state of condensation of mon temperature, and is converted into a fluid at very low temthe cyanogen and oxygen atoms, forming respectively cyanic acidand cyanuric acid, explains the difference in the properties of peratures, whilst the other is solid at the common temperature. If you saturate strong hydrocyanic acid with chlorine gas, you these two acids, exactly as in the instance of the numerous comobtain a solution of the gaseous chloride of cyanogen in water; binations of carbon with hydrogen, which, though possessing the upon the application of a gentle heat, chloride of cyanogen same per centage composition, exhibit dissimilar properties. The escapes from this solution in the form of gas. If you transmit this relative proportion of the atoms composing their elements is the gas through a tube containing fused chloride of calcium, so as to same, but the number of simple atoms which have combined to free it from moisture, and conduct it then into a vessel surrounded form a compound atom, is dissimilar in the various compounds. by a mixture of snow and common salt-(by which means a very According to this, we may express the constitution of the two high degree of cold is produced)-the gas is converted into a chlorides of cyanogen, and of the two acids ’respectively arising limpid fluid, which may be kept in glass tubes closed by fusion. from the transposition of their elements with the elements of I say, this fluid chloride of cyanogen may be kept, but I must water, as follows :add, that it does not preserve its properties intact, for in summer, 1 atom of gaseous chloride of cyanogen cry Cl when the external temperature is high, and the tendency of the 1 atom of anhydrous cyanic acid ...... cry 0 fluid to change into vapour becomes more powerful, so as to in1 atom of solid chloride of cyanogen... = Cy Cl3 crease the pressure in the small glass tubes, the fluid chloride of 1 atom of anhydrous cyanuric acid ‘ Cy3 Os cyanogen is observed to become gradually converted into white And thus we assume acid to be formed by the cyanuric may solid crystals, which consist simply of the second chlorine comor condensation of the elements of three atoms of pound of cyanogen-viz., the solid chloride of cyanogen, (solid at combination the common temperature.) Both these compounds have the same cyanic acid into one single atom. , The fact that cyanuric acid is more permanent, and less readily composition, as is evident from their analysis. We find in both of them one equivalent of chlorine to one equivalent of cyanogen. decomposed than cyanic acid, seems to militate against the Now if we assume the chlorine replaced by one equivalent ofgeneral rule, according to which, the force of affinity and,attraction which connects the molecular elements is less powerful in oxygen, we have the formula of cyanic acidcomplex than in simple atoms. This is, however, easily exCy + Cl = Chloride of cyanogen plained by the greater state of condensation in which the elements exist in cyanuric acid, and consequently the greater proximity Cy + 0 = Anhydrous cyanic acid. of the atoms to each other. The formation of cyanuric acid from Both chlorides of cyanogen decompose with water, transposing andl cyanic acid, as well as the decomposition of cyanuric acid, finda of with the elements the latter the substance ; combining gaseous explanation in this assumption. Cyanic acid and cyanuric chloride of cyanogen transposes with the elements of water, form- ready acid contain both the same elements, but the former is a simple ing hydrochloric acid and cyanic acid, and since the latter is not atom, whilst the latter is a complex atom. If we mix cyanate of persistent in contact with water, but transposes with the elements: potass with acetic acid, or with a small quantity of a strong-acid, of this body, forming carbonic acid and ammonia, which latter insufficient in amount to effect the complete decomposition of again combines with the hydrochloric acid, forming sal am-_: this salt, part only of the cyanate is decomposed, the decomposing moniac, we obtain by the transposition of the gaseous chloride acid sharing the potass with the cyanic acid, and thus liberating of cyanogen with four equivalents of water, one equivalent of sal a certain amount of cyanic acid; part of this liberated cyanic ammoniac, and two equivalents of carbonic acid. acid transposes with the elements of the water of the menstruum, Chloride of Hydrochloric Water. acid. forming carbonic acid and ammonia, whilst the remainder is acid. Cyanogen. Cyanic absorbed as hydrate by the still undecomposed portion of the Cl H Cy Cl + HO Cy 0 + cyanate of potass, and combining with the elements of this salt, 3 acid H 0 H Cl plus Cyanic plus transforms it into cyanurate of potass. The action of heat causes Carbonic Sal acid. ammoniac. C2 the complex atom of hydrated cyanuric acid to separate into= Cs 04 + Cl H, N H, three simple atoms of hydrated cyanic acid. H Cl to these views, the hydrate of cyanuric acid consists of From this manner decomposition we may infer that the of According one atom of anhydrous cyanuric acid, combined with three gaseous chloride of cyanogen is the compound corresponding to) atoms of water; and thus its constitution is similar to that of cyanic acid, and that these two substances have a similar con- phosphoric acid,-i. e., it is, like the latter, a tribasic acid. The stitution. comparison of the salts formed by phosphoric acid and by Now, if you bring the solid chloride of cyanogen into contactt cyanuric leaves no doubt as to the analogous nature of these with water, and apply heat, its elements transpose likewise with1 two acids.acid, the elements of the water, but instead of forming sal ammoniac PHOSPHATES. and carbonic acid, they form hydrochloric acid and cyanuric acid..................... Phosphoric == P 0;, + 3HO acid. It is obvious that the cyanogen in the gaseous chloride of exists in the same state and manner of combination as (Basic) Phosphate of silver = P O5 + 3 Ag 0 it does in cyanic acid, whilst the cyanogen in the solid chloride 2K0 of (neutral) Phosphate potass... (Neutral) potass = P 0 is contained in the same state and manner of combination as in KO cyanuric acid. We possess a very simple means with volatile = P (Acid) Phosphate of potass 05 + bodies, to ascertain whether the molecular arrangement of two substances of analogous composition differs or not. This means CYANURATES. is the determination of their respective specific weights when in == acid..................... Cyanuric Cyg O3 + 3 H 0 the gaseous state. We are thus enabled to ascertain what num= of silver ... ber of simple atoms their elements contain respectively in equal (Basic) Cyanurate Cys Os + 3 Ag 0 2 K- 0 volumes. The two chlorides of cyanogen are volatile, and admit (Neutral) Cyanurate of potass = Cy3 O3 of being weighed in their gaseous state. By comparing the relative weight of their gases in equal volumes, we are enabled to (Acid) Cyanurate of potass = Cy, determine whether their elements are arranged in a similar or dissimilar manner. Now this mode of determination has shewn The further consideration of this subject we will defer to the that the solid chloride of cyanogen contains, in the gaseous state, next lecture. ...
,
.
t .
í
H,
N Os 0)
-
1
cyanogen
......
...
......
= P 05 + 1 H 0 {KO +H{
...
O O3 + {K O ’