The Story of "Porphyroxine-Meconidine"


Merck's Discovery
Hesse's Meconidine
Rakshit's Porphyroxine
19 Isolation of "Porphyroxine-Meconidine"
Some Analytical Properties of "Porphyroxine-Meconidine"
Determination of the Origin of Seized Opium


Pages: 15 to 25
Creation Date: 1952/01/01

The Story of "Porphyroxine-Meconidine"

(The red-turning alkaloid of opium)

"Porphyroxine-meconicline" is the most mysterious of the opium alkaloids, but in recent years its true analytical properties have been learned Its percentage in opium is quite small, but in trying to determine the origin of illicit opium by scientific means, it is of value Its colorimetric determination gives a very helpful indication of origin, especially for differentiating between Indian and Iranian opiums

More than one hundred years ago it was discovered that opium contains an alkaloid characterized by the property of changing to a red-coloured compound when heated in dilute mineral acid; but this alkaloid is still rather mysterious. Even its elementary formula is not known. In the lists of opium alkaloids it often appears three times, once under a name,rhoeadine, belonging to another alkaloid of a different species of poppy, and under two other names, "porphyroxine" and "meconidine", with two completely different descriptions, both incorrect. It has also been known under the name "opine". At least five chemists, prior to 1947, claimed to have isolated it, but without having really accomplished the isolation. The descriptions they gave of its properties apparently apply to different bases; are inconsistent with each other; and have generally been unverifiable by others, except as to the red-turning, property.

In the last four years new researches have discovered no evidence for more than one red-turning alkaloid in opium; it is the same in all types of opium though varying greatly in amount, and its analytical properties have now been fairly well determined. It has, been isolated (1947), but not in sufficient quantity for determination of its chemical constitution It seems best, in view of the past mistakes, to wait until this is done before fixing upon a final name which will be associated with a true description. In the meantime, the red-turning alkaloid will sometimes be referred to as "porphyroxine-meconidine"; the hyphenated name indicating that just one alkaloid is meant, which has been known under the names "porphyroxine" and "meconidine", while the quotation marks are used because the descriptions under these names do not entirely correspond to the real alkaloid, and, in fact, neither "porphyroxine" nor "meconidine", as previously separated and described (before 1947), has any real existence as a correctly described, individual alkaloid.

Merck's Discovery

The red-turning alkaloid was discovered by E. Merck in 1837 in Bengal opium, and named "porphyroxine" [1] , [2] * He mentioned that he also found it in Smyrna (Turkish) opium. Thebaine had been discovered only two years before, morphine, narcotine, codeine, narceine, and pseudomorphine were also known at the time, and the non-basic substances meconin and meconic acid Pseudomorphine is an oxidation product of morphine and probably not a natural alkaloid of poppy juice If narceine is counted as one of the major opium alkaloids - it is usually sixth in amount - then porphyroxine was the first of the natural minor alkaloids of opium to be discovered. It is ironical that there is still so little known about it.

In 1837 quite a number of opium alkaloids were still undiscovered. Of these, at least papaverine and cryptopine, and probably laudanine and one or two others, normally exceed the red-turning alkaloid in amount.

Merck gave the following analysis for his sample of Bengal opium in parts per 100 8 morphine, 5 narcotine, 0.5 codeine, 1 0 thebaine, traces of meconin, 0.5 porphyroxine

The porphyroxine, precipitated with thebaine by ammonia, and separated by crystallizing the thebaine from ether, which left the porphyroxine as a resinous mass, was certainly anything but a pure substance The pure red-turning alkaloid probably does not exceed 0.1 percent in the usual Indian opium, though possibly it may sometimes be as high as 0 2 per cent. Although Merck stated that it crystallized in fine glistening needles, this was probably a partial crystallizing out of some other substance, and Merck himself concluded.

Superior figures in the text indicate reference to the bibliographic notes at the end of this article.

"When, as I hope, I succeed in obtaining this substance pure enough, that the elementary analysis can be undertaken, and when it has been confirmed thereby as a new constituent of opium, then I propose to name it porphyroxine (from purple and acid)."[1]

Merck said that the new substance "isneither basic nor acid" - he did not say that it was an alkaloid, but this seems to have soon become the accepted idea

Apparently, the time never came that the elementary analysis was determined, but nevertheless, porphyroxine was generally accepted as a constituent of opium during the next thirty years. Chemists writing about opium sometimes referred to it, and there were several articles about it, which are now very hard to track down

Merck was responsible for another small item, relating to the use of the red-turning property of porphyroxine as a test for the presence of opium in forensic cases [3]

Riegel gave a different and apparently inconsistent method of separating porphyroxine from opium, it was extracted by ether with narcotine, and then separated[4] Riegel also claimed a crystalline product, but did not give the elementary formula or any other additional information about chemical properties

The foregoing researches were included by J J Berzehus in his Lehrbuch der Chemie, 1848, and were, therefore, well known to chemists of the time Berzehus disliked the name "porphyroxine", and proposed the name "opine". He classed it among the organic bases °

In 1852, an article by Robertson concerned chiefly the use of "porphyroxine" or "opine"in forensic cases to show the presence of opium, without adding any important information on chemical properties.[6]

Porphyroxine was included in at least three studies of the pharmacological properties of opium alkaloids, by Albers, Fronmuller, and Baxt.7,8,9Albers and Fronmuller, it seems, both used porphyroxine supplied by Merck No new information concerning the isolation of the alkaloid or its chemical properties was provided.

Hesse's Meconidine

The situation was changed completely by the researches of Hesse, which did so much to elucidate the composition of opium, but nevertheless, as far as the red-turning alkaloid was concerned, came nearer confusing the few facts that were already known

Hesse discovered rhoeadine in Papaver rhoeas in 1865,[10] and soon afterwards published two articles about it11,12 Papaver rhoeas is the common red "corn poppy" or "field poppy" of Europe In cultivation for floral purposes it has numerous colour varieties, of which the Shirley poppies are especially well known

In 1866 Hesse discovered or verified that opium contains a red-turning alkaloid, and at once jumped to the conclusion that it was rhoeadine[11] He did not say anything about previous knowledge of porphyroxine except to refer slightingly to Merck's discovery as follows "Merck noted this coloration a long time ago, without being able to prepare the reactive substance, for the porphyroxine, as he called it, contained less than 1 per cent of rhoeadine"

Since the red-turning substance in opium is not rhoeadine, Hesse's remark about its percentage in Merck's porphyroxine was merely an incorrect guess. However, this is the insecure foundation of the idea that opium contains rhoeadine Even recently, commentators have said that Hesse "found rhoeadine" in Merck's porphyroxine

Three years later (1869), Hesse acknowledged that opium does not contain rhoeadme, but a different alkaloid[12] In the next year, 1870, he published his account of "meconidine" ,as he renamed the red-turning alkaloid [13]

Hesse's meconidine was never obtained crystalline, nor were any of its salts, and undoubtedly it was merely a mixture of phenolic or acidic alkaloids. The preliminary partial purification of the bases that Hesse then investigated included their extraction by dilute acetic acid from chloroform, a process that may well have involved the loss of a large part of these bases, especially of the red-turning alkaloid. At any rate, he obtained a more or less purified solution of bases dissolved in KOH, containing codeine and the bases he named meconidine, codamine, laudanine, and "Base X"

The codeine was removed by shaking out the alkaline solution three times with ether, "itgoes over into ether much quicker than the other four bases" - from alkali, at any rate The bases were then freed from alkali combination with NH 4Cl and obtained in etheral solution With slow evaporation of the ether, laudanine first crystallized out On further concentration, an amorphous deposit was obtained. On addition of some fresh ether, washing with aqueous solution of NaHCO 3, and further spontaneous evaporation, crystalline codamine was obtained As soon as an increase of these crystals was not noted any more, the bases remaining in the ether were transferred to solution in dilute acetic acid, and this aqueous solution then saturated with NaCl A resinous precipitate formed, which according to Hesse was meconidine hydrochloride "Base X"remained in solution, apparently no further information about this base was ever given, presumably it is an "undiscovered" phenolic alkaloid The meconidine hydrochloride remained non-crystalline even after several re-solutions with dilute acetic acid and re-precipitations with sodium chloride had freed it completely, according to Hesse, from traces of "Base X" The "pure salt" was dissolved in water, NaHCO 3 added, the alkaloid extracted with ether, and the etheral solution filtered with some purified animal charcoal Still the free base did not crystallize, either.

Hesse purified codamine from adherent meconidine by dissolving the crystals in dilute sulphuric acid and boiling, to convert the meconidine to the red compound, and then treating with animal charcoal to de-colorize the solution, from which the codamine could then be recovered After boiling some of the meconidine itself in dilute sulphuric acid, Hesse reported that "animal charcoal takes the changed substance out of a neutralized solution very readily, and then the solution contains no organic base any more". This seems to be what he relied on to classify meconidine as an isolated individual base.

In this article Hesse acknowledged that "meconidine agrees with rhoeadine only in small points". Concerning Merck's porphyroxine he now said, "This coloration was first observed by Merck, who was, however, unsuccessful in isolating the reactive substance, for the porphyroxine,which Merck described as the red-colouring, opium substance, is a mixture of several bases, among which is meconidine, as I call the substance One can easily be persuaded of the heterogeneous character of porphyroxine if one subjects it to the same analytical treatment as I describe for the ether extract of opium solution." Undoubtedly Merck's porphyroxine was a mixture, but it does not appear that Hesse ever actually analysed it, or any mixture obtained by following Merck's directions, although his remarks, have sometimes been referred to in that sense

In 1881 a brief article by Dey discussed again the use of the porphyroxine colour reaction as a test for opium in forensic chemistry.[14] Dey was working in India, and while he did not specifically recommend the test for the purpose of distinguishing Indian opium from Turkish, he remarked incidentally, "This constituent is not present in Turkey and Smyrna opium", and "If Turkey opium is employed for poisoning no porphyroxine can be found" This of course is incorrect; but, as the Secretariat chemists have observed, Indian opium does usually contain a great deal more "porphyroxine-meconidine" than other kinds, so it is possible to make the test in such a way that generally,only Indian opium would respond The clearest distinction, however, is between Indian and Iranian opiums.The opium from certain districts in Turkey (Zile and Malatya) is likely to contain as much "porphyroxine-meconidine" as even the highest in Indian opiums.

A brief note in 1930, by Bamford, corrected Dey's observations to the extent of noting that Turkish opium does give the test[15]

Rakshit's Porphyroxine

In 1919, Rakshit published his account of the isolation of porphyroxine[16] This was the most detailed thus far and convinced most readers, at first, that an alkaloid properly named "porphyroxine" had really been isolated at last In 1926 Rakshit published an article on the chemistry of porphyroxine, in which amongst other properties described he said that it was converted to codeine by heating with hydrogen peroxide in 2 per cent KOH solution, and he assigned to it a structural formula closely related to codeine [17]

Small later remarked that the structural formula proposed involved a "return to the improbable Pshorr formula" for codeine [18]

To elucidate the structure, Rajagopolan attempted to obtain porphyroxine as described by Rakshit He was not particularly interested in the red-turning property but in porphyroxine as an alkaloid closely related to codeine All he could find in this sense was codeine itself, and he suggested that Rakshit's porphyroxine might be nothing but impure codeine 19,20 A further study of Rakshit's articles and some experiments by the Secretariat now make this virtually certain This in no way disposes of the real red-turning alkaloid, which certainly exists, but its structural formula is unknown and it is not even known whether it is one of the "phenanthrene alkaloids" of opium.

As Rajagopolan pointed out, Rakshit did not even mention codeine as present in describing his method of separating porphyroxine, and so did not explain how he considered he had separated his porphyroxine from codeine - or from the other known alkaloids either, for that matter He did say that as a matter of "striking contrast" in properties, "unlike codeine, the aqueous solution of its hydrochloride gives a white or pale yellow precipitate with ammonia".[21] This could easily be due to impurities, which, of course, included a certain amount of the real red-turning alkaloid.

Rakshit's values for codeine in typical samples of Indian opium, given in another article,[21] were only about half the amount now recognized as present,[22] as was also pointed out by Rajagopolan.[20] In this article Rakshit criticized the earlier codeine method of Annett and Sen, saying, "The authors appear to have taken no precaution to remove porphyroxine, which is always extracted to some extent by almost all immiscible solvents from the lime solution of opium and in a moderate degree by toluene"He went on to say concerning thebaine, meconidine, codamine, laudanine, protopine, and porphyroxine "with the exception of porphyroxine, these are only nominally present in Indian opium".[21]

Rakshit did not state the yield of his porphyroxine in giving his method of obtaining it,[16] but the foregoing quotations incontestably show that he considered it occurred well in excess of the usual minor alkaloids and that it was capable of substantially affecting the codeine determination even if only partially extracted, and that in Indian opium it even exceeded thebaine, which was only "nominally" present

Rakshit's method was the following[16] (with comments)

Opium was triturated with freshly-slaked lime, water added, the solution obtained was filtered and the filtrate extracted with ether. The ether was dried with calcium chloride, filtered, and evaporated A quantity of the powder so obtained was extracted five times with boiling light petroleum.

Here occurs a startling ambiguity Those who have previously summarized the method have considered that it was continued with the residue not dissolved by the light petroleum,23,18,and this is the natural reading, but actually Rakshit does not quite say this. He only says, "finally the contents of the flask were collected, dried, and powdered". In view of the fact that the porphyroxine was later extracted with light petroleum and re-crystallized from that solvent, it seems strange to extract the alkaloidal mixture earlier with light petroleum and discard the extracts; and possibly "the contents of the flask" means the light petroleum extracts. However, if the final porphyroxine is conceded to be mainly codeine, it does not make much difference which part is used, as the codeine would be partly but, certainly not completely removed in five extractions with light petroleum.

At any rate, the dried and powdered "contents of the flask" were treated with 10 per cent HC1 during half an hour, then diluted with an equal volume of water added gradually during one hour, and filtered (This hour and a half in solution in strong mineral acid can hardly be conducive to isolating the red-turning alkaloid unchanged ) The solution was then treated with NaHCO 3 to slight excess, and after half an hour filtered There was no statement as to what this accomplishes, but in fact it removes a considerable part of the papaverine and thebaine present, leaving the codeine in solution. Clearly, the method as a whole primarily separates a portion of the codeine

The remaining steps were, the filtrate was extracted four times with chloroform, the solvent evaporated, and the dried, powdered residue extracted with heated light petroleum This on evaporation yielded pale yellow prisms, melting at 134-135°,and declared to be porphyroxine.[16]

Some experiments of the Secretariat throw further light on the process

Since Rakshit's porphyroxine is declared to be present in the lime-water extract of opium, and to be non-phenolic and non-acidic, and somewhat soluble in light petroleum, a lime-water extraction of 5 grammes of Indian excise opium was made and the liquid extracted continuously with petroleum ether in an extraction apparatus for about five hours The petroleum ether extract was evaporated to a small volume, whereupon, on removal from the steam bath, the larger part of the alkaloids precipitated, and were filtered off and washed with a little fresh petroleum ether. The petroleum ether solution was then evaporated and the two portions of alkaloids examined separately, with the following results:

(A) Portion more soluble in petroleum ether.0 0993 gramme.

(B) Portion less soluble in petroleum ether 0 1450 gramme.


Alkaloids from A

Alkaloids from B

Weight (gramme)
Per cent
Weight (gramme)
Per cent
0079 8.0 0183 12.6
0399 40.2 0147 10.1
Codeine plus cryptopine
0412 41.5 1008 69.5
0890 89.7 1338 92.2


Total of the alkaloid in the two portions (gramme)

Percentage of the opium

0262 0.52
0546 1.09
Codeine plus cryptopine
1420 2.84
Portion of the petroleum ether extract not account- ed for by these alkaloids
0215 0.43

The amount of red-turning alkaloid in the petroleum ether extract was insignificant in comparison with the amount in the opium used. Most of the small amount present was taken out by alkali, in making the separations, a very little remained in the thebaine residues, but none with the codeine.

The larger papaverine residue and the four thebaine and codeine-cryptopine residues crystallized completely. It will be noted that the thebaine in this Indian excise opium, soluble in the lime-water solution and extractable by petroleum ether, exceeded 1 per cent (by weighing). The codeine crystallizes with one molecule of water of crystallization; the percentage of anhydrous codeine (plus cryptopine) was, therefore, about 267 per cent. The codeine determination on this opium by the method used by the Secretariat, [22] involving ether extraction from the lime-water solution, was 3 07 per cent anhydrous codeine, or 3 27 per cent crystalline

In these determinations no treatment with NaHCO 3 was used Another extraction of lime-water filtrate representing 6 grammes of the same opium was then made, this time with ether The residue from the ether was treated five times with petroleum ether, which was then evaporated In view of the ambiguity in Rakshit's method, both portions, that dissolved by petroleum ether and that remaining, were separately studied Each was dissolved in dilute acetic acid, filtered, treated with NaHCO 3, and after standing for about half an hour, again-filtered The filtrates were extracted with chloroform. This solvent was evaporated and the residues examined without again extracting with petroleum ether.

Dissolved by petroleum ether and extracted from NaHCO3 filtrate - 0635 gramme.


Weight (gramme)

Percent of residue

Comparative porphyrycolourobtained

0050 7.9
0134 21.1 0.6
Codeine plus cryptopine
0408 64.2
Phenolic or acidic residue from thebaine separation
0015 2.4 5.6
0607 95.6

Not dissolved by petroleum ether, extracted from NaHCO 3 filtrate - 0.2530 gramme.


Weight (gramme)

Percent of residue

Comparative porphyrycolourobtained

0085 3.4
0452 17.9 2.0
Codeine plus cryptopine
1537 60.7
Phenolic or acidic bases:
From papaverine extraction
0009 0.3 1.25
From thebaine extraction
0049 1.9 36.0
After codeine extractiona
0151 6.0 0.5
2283 90.2

a Some morphine was present, which chiefly accounts for the size of this residue, even though not all the morphine present was re-extracted

The method of separation was briefly as follows. The mixture of alkaloids was transferred to a separatory funnel by means of CCl 4 and about 7 cc of unbuffered dilute acetic acid solution A wash solution of dilute acetic acid was used and the papaverine shaken out with CCl 4, the extracts shaken with alkali solution and then with three solutions of 2 per cent sulphuric acid The papaverine was then recovered from the sulphuric acid solutions (There was no evidence of narcotine ) The acetic acid solutions were then buffered with sodium acetate and the thebaine shaken out with CCl 4, the extracts being shaken with two portions of rather strong alkali solution and then washed with water, filtered, and evaporated As will be seen from the figures above, practically all the red-turning alkaloid was in the CCl 4 with the thebaine, but nearly all of it was held by the alkali solutions, indicating a phenolic or acidic character for the true "porphyroxine-meconidine". The buffered acetic acid solutions were then made alkaline and the codeine and cryptopine extracted Nearly all the cryptopine was here (also any protopine, not considered separately from cryptopine in these determinations), only traces getting into the thebaine residue. The various alkali solutions were acidified, then made ammoniacal, and extracted for the phenolic or acidic bases.

The total codeine (plus cryptopine) if the two portions was 3 24 per cent of the opium, checking almost exactly with the previous codeine determination on 2 grammes of this opium of 3 27 per cent crystalline codeine (3 07 per cent anhydrous). The total thebaine, even with the NaHCO 3treatment, was 0 98 per cent Also, it will be noted that the ratio of thebaine to the other bases present is increased by petroleum ether extraction The total papaverine was 0 22 per cent of the opium, it is limited in amount by the use of a lime extract and by the NaHCO 3treatment Probably the proportions of thebaine and papaverine in a final product would be less by working on a larger scale, as Rakshit did, but there is nothing in his procedure to indicate that they were eliminated.

From these experiments it is clear that Rakshit's porphyroxine can only have been primarily codeine, with impurities of thebaine and papaverine and a small proportion of the real red-turning alkaloid. The thebaine impurity may well have been considerable In fact, Rakshit states that after recrystallizing three times from petroleum, his porphyroxine gave a red colour with concentrated sulphuric acid, and orange with concentrated hydrochloric acid [16] In the circum-stances, these reactions must be attributed to thebaine, although the real "porphyroxine-meconidine" does turn red, dissolving to a brick-orange colour soon changing to brown, when treated with concentrated sulphuric acid (Some of its other colour reactions are given later.)

In 1926 in a long article Machiguchi reported percentages for virtually all the known opium alkaloids in Japanese opium, but with very few new facts concerning them or the methods of separation [24] He reported 0 25 per cent meconidine Concerning porphyroxine, he said that a crystalline substance was obtained resembling Rakshit's porphyroxine and having the same melting point, but that analysis showed it to be a mixture of codamine, laudanine, and meconidine This reflects Hesse's statement concerning Merck's porphyroxine, quoted earlier, but certainly these bases, all phenolic, could not possibly have constituted Rakshit's porphyroxine.

19 Isolation of "Porphyroxine-Meconidine"

In 1947 Fulton, working at the United States Bureau of Narcotics on the problem of determining the origin of seized opium by chemical and physical means, undertook the isolation of the red-turning alkaloid from approximately 2 pounds of seized Indian opium His results were given in a short mimeographed paper which was published in 1948 in a United Nations document, having been communicated to the Commission on Narcotic Drugs by the representative of the United States of America[25] The method of separation, not given in detail in the paper mentioned, was essentially as follows

  1. The opium, 870 grammes, was extracted with lime-water in several portions, a total of 250 grammes Ca(OH) 2 and 7,500 cc. water being used The solution was filtered.

  2. The filtrate was put in a large round-bottom flask and extracted continuously with ether for 115 hours, operative time. The ether was changed in the receiving flask several times. This extractor was not very efficient and the long extraction was necessary to get out nearly all the "porphyroxine-meconidine" Even at the end, traces of this alkaloid were still being extracted as well as some "alkaloid 5". The latter as a base, probably phenolic, that gives a the-baine-like reaction with sulphuric acid This left in the aqueous solution most of the morphine, narceine, and the bases designated in this investigation as alkaloid 3 and alkaloid 4. The "porphyroxine-meconidine" was designated as alkaloid 1.

  3. The ether was evaporated off, and the residue of alkaloids taken up in dilute acetic acid (about 5 cc. glacial acetic acid in a total of about 140 cc water). The solution was then buffered with 25 grammes sodium acetate and extracted continuously with carbon tetrachloride. This left in the aqueous solution practically all the morphine and alkaloid 3 that had been extracted by the ether in the preceding step, and a large part of the codeine and alkaloid 5

  4. The phenolic alkaloids were now shaken out of the CCl 4 with NaOH solutions of gradually decreased strength (10 to 2 per cent), until all of the alkaloid 1 was in the aqueous solution, and the NaOH solutions washed with fresh CCl 4 until the non-phenolic alkaloids were removed This is a tedious process The "porphyroxine-meconidine" clings to the other alkaloids and it is almost impossible to remove all of it from the CCl 4, solution of non-phenolic alkaloids, however, nearly all was separated The CCl 4 removes the codeine, thebaine, cryptopine, and papaverine Narcotine is virtually insoluble in lime-water solution, but if any were present at would also be removed here, likewise any very minor non-phenolic alkaloids which have not been separately distinguished in these investigations, e.g, protopine, neopine, and laudanosine

  5. The alkaloids which, although phenolic, are extractable by chloroform from alkali, were then shaken out Since these are about the same phenolic bases that can be taken out of lime solution by a long, continuous ether extraction, very little further separation of alkaloids was accomplished, except to make sure of the complete elimination of morphine and alkaloid 3 and perhaps most of any remaining alkaloid 5, by leaving them in the aqueous alkali Since the volume of alkali solution from the preceding step was rather large, this main solution was acidified with acetic acid, then made ammoniacal, and shaken out with chloroform; the chloroform extracts were then shaken in turn with two alkali solutions before being shaken with a dilute solution of ammonium salt and then with water At this point the alkaloids still present in the chloroform extract, so far as found later, were the following.

    Alkaloid 1 - "porphyroxine-meconidine"

    Alkaloid 2 - probably laudanine *

    Alkaloid 6 - a weak base (possibly lanthopine or narcotoline)

    Alkaloid 7 - a base yielding colour reactions like those of alkaloid 3, but extractable by CHCl 3 from alkali.

    At the time, the presence of alkaloids 6 and 7 was not known; they were discovered at a later stage

  6. At this stage, it would probably have been best to reduce the chloroform solution to a smaller volume and shake out the alkaloids, to removal of alkaloid 1, with dilute acetic acid, leaving most of the alkaloid 6 in the chloroform However, the desirability of this purification was not recognized at the time, and the chloroform was evaporated off Another trial of continuous extraction by CCl 4 from buffered acetic acid solution was made on a portion of the residue but did not accomplish much separation, a hand shake-out was then decided on. The residue of bases was treated with 5 per cent acetic acid and the solution buffered with sodium acetate in the proportion of 4 grammes per 10 cc. Whitish burrs of crystals formed in the buffered solution. At the time, these were left in the process, but in any future separation on a larger scale it would doubtless be best to filter off this precipitate and at least process it separately, whether it consists mainly of alkaloid 1 or alkaloid 2 The solution was shaken out at room temperature with carbon tetra-chloride, using three wash solutions of buffered acetic acid, in small volumes The extracts were shaken with dilute ammonia and then water The extraction was a very long process Occasionally the wash solutions were each poured back one step and a new one added, to prevent gradually carrying the alkaloid 2 and alkaloid 7 past them The first two portions of CCl 4 were set aside because of high content of alkaloid 6, the many additional extracts were evaporated At this stage the alkaloid 1 crystallized readily, but it was-still rather brown and not yet completely free of other alkaloids The weight was 728 mg Alkaloids 2 and 7 were largely left in the solutions of buffered acetic acid

Some recent experiments on known laudanine, obtained by the kindness of Professor Fuchs. Head of the Pharma-cognostical Institute, University of Vienna, from the Spath collection, have shown that. contrary to earlier statements. laudanine is extractable by chloroform from 2 per cent NaOH solution.

The remainder of the process as actually performed involved so many partial separations and recombinations that it is difficult to summarize, but the two chief methods of further separation will be given

  1. A petroleum ether extraction was undertaken with the intention of freeing the base from the brown colour, but it proved to be more effective in separating the other alkaloids from the alkaloid "porphyroxine-meconidine". The residue of bases was treated with 10 per cent acetic acid until disintegrated, poured into the extraction apparatus without filtration, and made slightly ammoniacal. A fairly copious precipitate formed, which showed almost no tendency to dissolve in the petroleum ether. A two-hour extraction yielded a nearly colourless extract and a residue which contained some crystals but as a whole refused to crystallize. It was a mixture of alkaloids 1, 2, 6, and 7 while the greater part of the precipitate of alkaloid 1 remained in the extractor At this point, it would probably have been best to continue the extraction with pure ethyl ether, or if necessary, ether-acetone. Actually, the alkaloid 1 was recovered by using successively benzene, benzene-acetone, and benzene-isopropanol, but each change of solvent brought over colouring matter also.

  2. Another method of separation was the following: The mixture of bases was dissolved in dilute acetic acid and shaken in a separatory funnel with CCl 4. This takes out alkaloid 6, but so slowly that the solvent was finally changed to chloroform This removes alkaloid 6 readily, but also a considerable part of the alkaloid 1. Accordingly it was necessary to back-extract the chloroform with small volumes of dilute acetic acid, then to shake out with chloroform again, and again back-extract with dilute acetic acid Finally, the acetic acid solutions were combined, made ammoniacal, and shaken out with CCl 4 The CCl 4 extracts were shaken with two small volumes of buffered acetic acid (to remove any remaining alkaloids 2 and 7),and then with a small volume of dilute ammonia, and finally with water This yielded some isolated "porphyroxine-meconidine"nearly pure, but there are two difficulties with the procedure First, the alkaloid 1 becomes more and more sensitive to acid as it is purified, and at this stage even the solutions in 5 per cent acetic acid begin developing the purplish red colour on standing a short time Therefore, this extraction, as a means of removing alkaloid 6 and some colouring matter, probably should be made at an earlier stage (see step (6)) Secondly, the purified alkaloid 1 has only a slight solubility in CCl 4, and is only slowly extracted by this solvent even from an ammoniacal solution In fact, the CCl 4 extraction was finally discontinued, and the remainder of the alkaloid extracted with chloroform These CHCl 3 extracts, following the CCl 4 extractions, were not shaken with buffered acetic acid, but were washed with water and evaporated Chloroform is a relatively good solvent for the alkaloid 1, but also extracts more impurities than does CCl 4 This extraction also yielded some isolated "porphyroxine-meconidine"fairly pure

The two best residues of "porphyroxine-meconidine", amounting to 273 mg, melted fairly sharply at 175°. They were thought to be free of other alkaloids, but were still slightly brownish

In other residues, containing varying amounts of alkaloids 2, 6, and 7, more alkaloid 1 was present, to a total of possibly 0 5 gramme Allowing for losses, it still does not seem that the total amount can have exceeded 0.1 per cent of the opium (870 mg ) This opium had a comparative colour-value for "porphyroxine-meconidine" of 35 This is high, but a few samples of opium have been found even as high as 70 It seems, therefore, that this alkaloid may reach, at most, a maximum of about 0 2 per cent of the opium. The average in Indian opium would probably be somewhat under 0 1 per cent, in Turkish opium, around 0 03 per cent, in Iranian opium, little, if any, more than 001 per cent (See the graph of comparative values, given later.)

Some Analytical Properties of "Porphyroxine-Meconidine"

The following account of properties is taken from Fulton's paper,[25] slightly revised The red-turning alkaloid of opium is soluble in alkali and is presumably a phenol. It can be extracted from solutions either weakly basic or weakly acidic, by most organic solvents, but most extractions are very hard to make complete This is partly because this alkaloid has a rather limited solubility in most solvents, in addition, separations are particularly difficult because the "por-phyroxine-meconidine" seems to cling to some of the other alkaloids Thus, carbon tetrachloride will at first take out most of it even from a fairly strong alkali solution, apparently because it accompanies the other alkaloids that are extracted (it is very hard to separate it completely from thebaine), and the reverse extraction is difficult But after such a separation has been made, the "porphyroxine-meconidine"can scarcely be extracted by carbon tetrachloride from alkali, and the reverse extraction, with alkali from carbon tetra chloride, is much easier In fact, when separated from the other phenolic alkaloids, "porphyroxine meconidine" has only a slight solubility in carbon tetra chloride, and is difficult to shake out with it even from a slightly ammoniacal solution Chloroform, how ever, will still extract it from alkali after it has been separated from the non-phenolic alkaloids (This is true also of some of the other minor phenolic alkaloids of opium.) From an unbuffered acetic acid solution "porphyroxine-meconidine" is practically not extracted by carbon tetrachloride, but is extracted by chloroform; if the solution is buffered with sodium acetate the alkaloid is then extracted with some difficulty by carbon tetrachloride, or readily by chloro form .The purified alkaloid appears to be more soluble in benzene than in carbon tetrachloride Its solubility in ether is-rather low, and in petroleum ether very slight; but in the presence of the other minor phenolic alkaloids which are soluble in these solvents, it is extracted. Chloroform is a good solvent for "porphyroxine-meconidine", but likely to take out unwanted substances also, not only other alkaloids, but also non-alkaloidal impurities

The colour reactions of the isolated base are as follows:

HNO 3 - brownish orangish yellow, becoming a stronger orangish yellow

H 2SO 4 concentrated - strikes red, dissolves brick orange, soon changing to brown

H 2SO 4(2+1)-negative, slowly pinkish, with heat purple-red.

HC1 concentrated - colourless, gradually pink, .heated, purple.

Frohde's reagent (molybdate in sulphuric acid) - strikes red, soon changing to brown, then to very strong deep green to black green

Mecke's reagent (selenious acid in sulphuric) -strikes brick red, quickly fading and changing to brown, then develops very strong deep green to black green.

Marquis' reagent (formaldehyde in sulphuric acid) - brick red changing to dark brown

Ferric salt in H 2SO 4 - red changing to brown changing to dark green gradually

Persulphate in H 2SO 4 - red, at once changing to blue-green, changing to dull green (gradually fading).

The above reactions appear to be clearly related to those of rhoeadine and the alkaloid of Papaver glaucum, both of which also give the porphyry or purplish red colour on heating in dilute mineral acid Their most conspicuous reaction with certain sulphuric acid reagents is bright red, changing through brown to strong green Thus the alkaloid of Papaver glaucum shows 26

H 2SO 4 concentrated - strikes red, at once changing to intense brown yellow, gradually to intense green.

Marquis' reagent - strikes orange-red, at once changing to intense green

Rhoedme gives nearly the same With "porphyroxine meconidine", thc reaction with H 2SO 4 or with Marquis' reagent proceeds only as far as the brown colour, in the time of observation that was used, but with an oxidizing agent present, as with ferric sulphate in H 2SO 4, or persulphate in H 2SO 4, or Frohde's or Mecke's reagent, the green colour is obtained.

The best way of observing these reactions is to evaporate a little of the solvent containing the alkaloid in a small crucible, and apply the reagent to the thin film of the dry alkaloid on white porcelain.

If the isolated or nearly pure "porphyroxine-meconidine" is heated in (1 + 9) HC1, to transformation to the red compound, and the solution then allowed to stand at room temperature, the red compound very soon precipitates in crystalline form With a small proportion of other alkaloids present, red-plates may be formed, showmg a noticeable dichroism with polarized light (light to deep red) The isolated or nearly purified alkaloid gives dark needles or thin rods, often in rosettes or double sheaves The test can be made on the microscope slide with a minute amount. When the alkaloid is practically pure nearly all the colour crystallizes out of the acid solution Since this characteristic property seems not to have been mentioned by preceding investigators, it may reasonably be inferred that they had not even come very close to isolating the alkaloid responsible for the red colour of heated acid solutions

Determination of the Origin of Seized Opium

The possibility of determining the origin of seized opium by chemical and physical tests is currently the subject of an international research programme, in which chemists of Austria, Canada, Denmark, France, Germany, India, Israel, Japan, Netherlands, Norway, Turkey United Kingdom, and the United States of America, as well as the Secretariat of the United Nations, are taking part

The Secretariat chemists and the Canadian Government chemists, C G Farmilo and P M L Kennett, have studied the utility of a comparative determination of "porphyroxine meconidine" as a means of determining the origin of seized opium First results were very promising[27] [28] [29]

New samples of opium have been contributed .to the United Nations chiefly by the producing countries themselves, for international collaborative research A survey of "porphyroxine-meconidine" in these new samples has been made by the Secretariat, and a paper on the new data has been prepared simultaneously with this article and issued as document ST/SOA/SER. K/4[30]

The method consists essentially in extracting the opium with lime-water, then extracting a part of the lime-water filtrate (equivalent to one gramme of opium) wethether in a continuous extraction apparatus until no more "porphyroxine~meconidine" is coming over, evaporating off the ether and developing the red or porphyry colour from the alkaloidal residue by heating with.1 per cent HCl. The comparative values are given by the colour developed from the "porphyroxine-meconidine" of one gramme of opium, in 10 cc solution, read in the one-eighth inch cell in comparison with the red slides of the Lovibond tintometer

The accompanying chart combines all the available data for five of the main regions of opium production, and shows the comparative results. The curves repre sent eighty-eight samples from Turkey, thirty-two from India, thirty from Greece and Yugoslavia, twenty-four from Iran and twenty-one from Laos and Vietnam. Horizontally, the samples are simply arranged in their order of value for each curve, they are spaced more widely apart as the number for the curve is smaller The ordinates correspond to the colorimetric values obtained for "porphyroxine-meconidine" on the various samples

Full size image: 32 kB

Export samples of India, Turkey, and Iran are marked on the curves with circles The export opium of Turkey is made by mixing all the opium of the country, and thus in itself represents the average of Turkish opium The export samples of Turkey fall almost entirely on the lower half of the curve for Turkey as represented here. The significance of this is that in obtaining representative samples of different types, the varieties of Turkish opium containing high "porphyroxine-meconidine" have been over-represented, in comparison with the quantity of production. The Turkish export samples (values 9 4 to 14 4) indicate virtually the same curve as found for Balkan opium (Greece and Yugoslavia).

As is clearly seen, the samples from India generally have a much higher value in "porphyroxine-meconidine" than those from other countries A few samples from Turkey, however, rank with, or even above, the highest of the Indian samples all but one of these Turkish samples (having values above 35) were from Zile or Malatya, thus showing a regional difference within the larger region of Turkey In general the samples from Turkey, Laos and Vietnam, Greece, Yugoslavia, and most other countries from which the opium has been examined, gave intermediate values, while those from Iran gave much the lowest values

Since there is some overlapping of curves, the "porphyroxine-meconidine" value cannot be decisive alone, in determining the origin of seized opium. Rightly used, it is one of the best tests for the chemical determination of origin particularly in the wide distinction between the usual Indian and Iranian opiums The different positions of the curves for various countries, and in particular the consistent differences between the export opiums of India, Turkey, and Iran, are eloquent of the relation of "porphyroxine-meconidine" value to origin.



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