Med Facts Obs2819medfactsobsMedical Facts and Observations0952-4185Biomedical Journal Digitization ProjectPMC5110081PMC5110081.151100815110081291061841ArticlesExperiments and Observations to Investigate the Composition of James's PowderFrom the Same Work PearsonGeorgeM.D. F.R.S.17923279154128152010117920111201710112017https://creativecommons.org/publicdomain/mark/1.0/This work is free of known copyright restrictions. For more information, please see PMC Back Issue Digitization.pmc-status-qastatus0pmc-status-liveyespmc-status-embargonopmc-status-releasedyespmc-prop-open-accessyespmc-prop-olfnopmc-prop-manuscriptnopmc-prop-legally-suppressednopmc-prop-has-pdfyespmc-prop-has-supplementnopmc-prop-pdf-onlynopmc-prop-suppress-copyrightnopmc-prop-is-real-versionnopmc-prop-is-scanned-articleyespmc-prop-preprintnopmc-prop-in-epmcyespmc-license-refCC0 [ "8 J XIV. Experiments and Obfervations to inveftigate the Composition of James s Powder. By George Pearfon, M. D. F. R. S.- Vide Philofophical cTranfaclions of the Royal Society of London, Vol. LXXXI. for the"Tear 1791. Part II. 4-to. London, 1791. ALTHOUGH the powder, which is the fubje?t of the paper before us, has for more than thirty years been very extenfively ufed in the cure of continued fevers, the Public have not been accurately informed of the parti- cular nature of this fubftance. It was orio;i- nally a patent medicine; but it is well known that it cannot be prepared by following the di- rections of the fpecification in the Court of Chancery. Dr. Pearfon has, therefore, been induced to make it the fubjedt of chemical in- veftigation, and by a great, number of judicious experiments, fynthetical as well as analytical, has attempted to afcertain the nature and man- ner of preparing this medicine. He begins with defcribing its fenfible pro- perties. Some parcels of this preparation, he obferves, are white, but in general it has a yel- lowifli caft ; and this (hade is more evident in i fome C ] fomc fpecimens than in others. It is faid, that this powder cannot, in general, be made at dif- ferent times of precifely the fame fhade of yel- low or degree of whitenefs. Sometimes with the aid of a lens a few very fmall fhining fpicula are feen mixed with powder. When preffed be- tween the fingers it feels fmooth, with fome ra- ther rough particles, and it is gritty in the mouth. Moft parcels at firft are taftelefs; but in about a minute there is a flight brafly tafte. It is per- fectly inodorous. Dr. Pearfon next fpeaks of its fpecific gravity* He obferves that it feels much heavier than any of the common earths and ftones in a pulverized ftate. One of the phials, nearly full, in which it is fold, reckoned to hold a quantity equal to twelve packets, or 480 grains, contained 470 grains troy weight of James's Powder. This phial, filled with diftilled water to the fame height that it had been by the powder, was found to contain nearly four drachm-meafures, or about 240 grains, of this liquid. In another experiment made in a different manner, for the purpofe of afcertaining the fpe- cific gravity of this powder, the quantity which nearly filled a phial weighed 437 grains; and upon filling the fame phial, to the fame height, Vol. III. K with [ i3? ] with diftilled water, the temperature of which was 65?, the water weighed 250,2 grains. The reafon of the variation in thefe refults, in making ufe of different parcels of this medicine, our author thinks, will be obvious, from the account he gives of its preparation, and the great diffi- culty of determining, with accuracy, the fpecific gravity of powders. After defcribing the effects of fire on this fubftance, and obferving that the experiments made for this purpofe indicated the prefence of a metallic calx, a part at leaft'of which was that of antimony, mixed with earthy matter, he pro- ceeds to experiments with different menftrua, viz. water, the acetous, nitrous, and marine acids. From his experiments on James's powder with the fir ft of thefe menftrua, viz. water, he thinks we may conclude, 1. That the whole, or a part of it, is foluble, or at leaft may be fufpended, in about 2000 times its weight of pure water, cold ; and in about- half this quantity of boiling water. 2. That this folution contains calcareous earth united to an acid, or fome other fubftance, from which it cannot be difunited by cauftic or milcj, fixed alkalies. 3. That [ I3I ] 3. That this folution contains a metallic calx, a part of which at leaft is that of antimony un- combined, or at leaft not united to any acid with which it forms a compound foluble in water. 4. That the fubftance in a nitrous folution of the part of James's Powder that had been diffolv- ed in water, which was obferved to precipitate lime from lime-water, and which percipitate was not foluble in a large quantity of vinegar, is, probably, phofphoric acid from phofphorated lime decompofed by nitrous acid. The precipitation by muriated barytes and nitrated filver, which is defcribed as having taken place in two of the experiments, could not, our author thinks, be from vitriolic and marine acids confidently with the preceding experiments; and he could not have conjectured what was the in- gredient in James's Powder which occafions it, if he had not found, that muriated barytes is not only a teft of vitriolic but of phofphoric acid united to lime and alkalies; and that the acid of phofphorus will alfo produce a turbid appearance with nitrated filver. The prefence of calx of iron was detedled in thefe experiments, but in fo fmall a quantity that our author is inclined to confider it only as an accidental fubftance. K2' . His [ '32 ] His experiments with the acetous acid indicate the fame kind of fub(lances as the experiments with water, namely, calcareous earth in a com- bined ftate; phofphoric acid ; calx of antimony, and calx of iron. It appears alfo from thefe experiments that James's Powder is either wholly or partially foluble in about 300 times its weight of concentrated acetous acid. It appears from the experiments with nitrous acid, that this menftruum, by two affufions, in a large proportion, aided by trituration, digeftion, and heat, diffolved |?| of James's powder that had been expofed to the a<?tion of water and acetous acid ; but our author obferves, that from the fmallnefs of the quantity which was contain- ed in the nitrous acid the fecond time it was ap- plied, and from its being principally calcined antimony, not more than two of the fix grains afforded by the folution, perhaps, fhould be conlidered as diffolved, for the reft may be fuppof- cd to have been merely Jufpcndcd. The firft folution alfo in this menftruum, it- ieems, was not filtered, and the acid was confi- derably redundant, and there were found in it fe- veral grains of calcined antimony. The real quantity diffolved might, therefore, our author thinks, probably be eight grains lefs than the z ? above [ 133 ] above 108 ftated. According to this mode of calculation, the proportion of the foluble part of James's Powder in nitrous acid is or about tVo. 2. The whole of this foluble part, except a lit- tle calx of antimony, he thinks, is decifively phofphoric acid and calcareous earth : which two fubftances, he obferves, may reafonably be fuppofed, from thefe experiments, to have been united together, and to have been in the ftate of phofphorated lime in this powder. Confe- quentiy the proportion of this phofphorated lime, confidered as the. foluble part of James's Powder in the experiments in queftion with ni- trous acid, appears to be 40 per cent, making a deduction of 1 per cent. for the antimonial calx contained in the nitrous acid, in thefe ex- periments. He fufpects, however, that the powder which refilled folution in this menftruum may contain more phofphorated lime; and this confideration prevents him afiigning at prefent the above 40 per cent, as the whole quantity of it in James's Powder. It cannot, however, he thinks, be a fmaller proportion. He does not reckon the calx of iron in thefe calculations, becaufe it is in too fmall a quantity, and is apparently only to be looked upon as an accidental extraneous fubftance. He fuppofes K 3 too, [ *34 ] too, that the water and acetous acid applied to the James's Powder ufed in thefe experiments, carried off a proportion of its ingredients equal to that in the remaining powder. From the experiments the author next relates, we learn, that by repeatedly digeiling and boil- ing m marine acid, and in aqua regia, that part of James's Powder which refitted foiution in ni- trous acid, which was 77 grains were car- ried off by thefe menftrua ; but confidering the fmall proportion contained in thefe acids after the two firft affufions, which afforded 57,15 grains, and fuppofing the calx to be neither in- creafed nor diminifhed in weight by the acids, the real quantity of foluble and fufible calx of antimony, he. rhinks, may be ffated to be that of the Algaroth powder which he obtained in thefe experiments; for the other kind of antimonial calx procured by fubfequent affufions was pro- bably only fujpended. It appears, therefore, that 240 grains of James's Powder, afforded, by thefe experiments with marine acid, 57,15 grains of Algaroth powder, and 19,85 grains of a lefs foluble and more difficultly fuiible calx of antimony, with a fmall proportion of phofpho- rated lime. The refiduum, amounting to 55 grains, was next examined ; from his experi- ments; [ i35 1 ments, however, on this infoluble-matter, he could only conclude that it contained calx of antimony; but as to the proportion of this calx, and the other fubftance with which it is joined, he conjectures that it may be about half the quantity of the infoluble powder; and that the other half is antimonial calx and phofphorated lime, fo highly calcined and vitrified together as to refill folution in acid menftrua, decomposi- tion by charcoal, and fufion with fixed alkalies, but not by phofphoric acid. Our author obferves, that he fliould not have been fatisfied with here terminating this analyfis without enquiring further into the nature of this infoluble matter; but he difcontinued this ana- lytic inveftigation in order to derive light from fynthetic experiments. His experiments on this infoluble matter feem ' to (how, that the proportion of antimonial calx is not fo great as might have been affigned from the experiments with nitrous acid, marine acid, and aqua regia. The fubftances and proportions of them, ob- tained from 240 grains of James's Powder, were - as follow: K4 Phof- [ '36 J Grains. Phofphorated lime, with a little anti- monial calx, - - 100, Algaroth powder, - - Sl^S Infoluble antimonial calx, with a lit- tle phofphorated lime, - - The fame infoluble calx, with, proba- bly, a little phofporated lime, - 5/;, Wafte, ? - 8, 240,0 As it might be objected, that conclufions drawn concerning the nature of calces might be erroneous if nitrous acid had been applied pre- vioufly to fubftances containing them, our author made an experiment with marine acid applied ^0 James's Powder, which had not been exr pofed to the a&ion of nitrous acid, or any other menftruum. From this experiment he thinks it may, perhaps, be fairly concluded that the pro- perties of the calx in James's Powder are not altered by nitrous acid to affedt its folubility in marine acid. To know whether James's Powder contained any fubflance that could be decompofed by mild fixed alkalies, 100 grains of James's Powder were boiled in fix ounces of water, with fifty grains x[ 137 ] grains of mild alkali of tartar, for three hours, and then the remaining liquid was filtered, and evaporated to drynefs; but the matter left after evaporation was nothing but the alkali ufed in the experiment, with a little of the powder it- felf. The refult, we are told, was the fame on making the experiment with cryftallized mineral alkali inftead of alkali of tartar. Although the inability to prepare James's Pow- der would not prove the above conclufions, with refpect to its compofition, to be erroneous, the being able to compofe a fubftance pofleffing all the fame properties as James's Powder, by unit- ing or mixing together the fubftances ihewn by the prefent analyfis to enter into its compofition, would afford, our author thinks, all the proof and demonftration which can be had from che- * miftry. His analyfis, he obferves, fhewed no effential ingredients of James's Powder but xantimonial calces, phofphoric acid, and calcareous earth, which two laft fubftances appeared to be united together; but it would, he contends, have been .vain and unneceffary labour to have attempted to make this powder by mixtures of any of the commonly known calces of antimony and phof- phorated [ *3? ' ] ph orated iime; becaufe none of them, from their well-known qualities, could form a powder of the fame colour and fpecific gravity as James's Powder, and like it partially foluble in acids. From his experiments, however, the probability, he obferves, was evident, that this fubftance might be made by calcining together antimony and bone-afhes; which operation produces a powder called Lile's and Schawanberg's fever- powder ; a preparation difcribed by Schroder and other chemifts more than a century ago. The receipts for this preparation differ in the proportion of the antimony to the bone afhes, and in the ftateof the bone; fome directing bone (havings to be previoufly boiled in water ; others ordering them to be burnt to afhes before calcin- ing them with antimony; while in other pre- fcriptions the bone Savings are directed to be burnt with the antimony. According to a re- ceipt in the poffeffion of Mr. Bromfeild, by which this powder was prepared forty-five years ago, and before any medicine was known by the name of James's Powder, two pounds of hart's-horn (havings muft be boiled to diffolve O Pharmacop. Med. Chymic. 8vo. Lug. Bat. 1672, p. 428. all [ '39 ] all the mucilage, and then, being dried, be cal- cined with one pound of crude antimony, till the fmell of fulphur ceafes, and a light grey powder is produced. The fame prefcription, we are told, was given ro Mr. Willis, about forty years ago, by Dr. John Eaton, with the material addi- tion, however, of ordering the calcined mixture to be expofed to a great heat in a clofe veffel to render it white. Mr. Turner, it feems, made this powder above thirty years ago by calcining together equal weights of burnt hart's horn and antimony in an open veffel, till all the fulphur was driven off, and the mixture was of a light grey colour. He likewife was acquainted with the fad, that by a fuflicient degree of fire in a clofe veffel this cineritious powder turned white. *. Mr. Turner alfo prepared this powder with a pound and a half of hart's-horn fhavings * Dr. Pearfon thinks it probable that this powder was made for feveral years with merely the heat neceflary to carry oft the fulphur and calcine the bone, in an open veffel over a charcoal fire in a common grate, and confequently it was of a light clay orafh colour. In this manner, Mr. Bromfeild told him, he prepared Schawanberg's Powder 46 or 47 years ago. Its property of turhing white in a greater degree of fire appears to have been a fubfequent difcovery. and [ HO ] and a pound of antimony, as well as with imal- ler proportions of bone. Schroder prefcribes equal weights of antimony and calcined hart's horn; and Poterius and Michaelis, as quoted by Frederic Hoffman, merely order the calcina- tion of thefe two fubftances together (aligning no proportion), in a reverberatory fire for feveral days. In the London Pharmacopoeia of 1788, this powder is called Pulvis antimonialis ; and it is dire&ed to be prepared by calcining together equal weights of hart's-horn (havings and anti- mony. Our author obferves that powders made from various proportions of antimony and bone allies, after folution in nitrous acid, left a refiduum of antimonial calx much lefs or greater in quantity than James's Powder did by the fame menftruum, except two of Mr. Turner's pro- portions, viz. two parts of antimony and one of calcined bone, and equal weights of bone (hav- ings and antimony. The quantity of this calx was, however, greater, it feems, in the powder from the former of thefe two laft proportions than the latter of them; which latter corre- fponded fometimes exadtly, and always nearly, with the weight of the calx from a given weight of James's Powder. This calx afforded alfo, we C '4' ] we are told, the fame proportion of Algaroth powder as the calx in James's Powder; and the infoluble part of the calx afforded metallic grains like thofe from the infoluble part of the calx in that powder. Dr. Pearfon found then an exa?t correfpon- " dence between what he confiders to be the effen- tial and peculiar properties of James's Powder, and the properties of a powder made by uniting or mixing together the ingredients of James's Powder found by analyfis. But, in order to fhow the identity or difference of the qualities of thefe two fubftances, he made comparative obfervations on them, and repeated his ana- lytic experiments on James's Powder with the preparation made by calcining together equal weights of bone (havings and antimony, in an open veffel, to carry off the fulphur, and then in clofe veffels, applying fuch a degree of fire as to render them white, that is, on the fame pre- paration as the Pulvis antimonialis of the Lon- don Pharmacopoeia. Firft, he compared, more particularly, the fenhble qualities of feveral different fpecimens of James's Powder with various parcels of the Pulvis antimonialis made by different chemifts. All of thefe, he obferves, would be called white powders, [ >4* ] powders, but not two of them were fo in the fame degree. Moft of the papers of the Pulvis antimonialis were whiter than thofe of James's Powder; but others were of a very light ftone co- lour, and foirie had a (hade of yellow, fo as to re- ferable very exaftly James's Powder ; but all the parcels of James's Powder had either a fhade of yellow or of ftone colour, and none were perfedly white, or lo white as fome fpecimens of the Pulvis antimonialis. Some of the parcels of James's Powder and of the Pulvis antimoni- alis tailed brafty ; and other fpecimens of both powders, had no tafte. All of thefe powders were gritty. Moft of the parcels of the Pulvis antimonialis were a little fpecifically heavier than thofe of James's Powder. The fpecific gravity xof both powders was increafed by expofing them to fuch a degree of fire as brought them into almoft a femi-vitrified ftate; and on the con- trary, the fpecific gravity of the Pulvis antimoni- alis was lefs than it is in its ufual ftate, when made in fuch a degree of fire that the mixture preferves the powdery form. x The experiments with water on the Pulvis an- timonialis .produced, we arc told, the fame kind of appearances, but more flight 1 y than thofe with James's Powder; for the hot folution of i the . [ '43 J the former grew lefs milky on cooling than chat of the latter, and on evaporation to drynefs lefs fediment was found of the folution of Pulvis an- timonialis than after that of James's Powder. The experiments with acetous acid on the Pulvis antimonialis fhevved that this menftruum diflolved fometimes a greater, and fometimes a fmaller proportion of it than of James's Powder; and the diflolved matter was found to be anti- monial calx, phofphorated lime, and calx of iron, and no other fubftance. The proportion of foluble matter in nitrous acid was the fame, it is obferved, or nearly fo, of the Pulvis antimonialis as that of James's Powder; and this diflolved matter was phof- phoric acid, calcareous earth, with a little anti- monial calx, and a minute portion of calx of iron, as exactly as could be expedted from the nature of the fubftances and the experiments, in the fame proportion as thofe in James's Pow- der. The Algaroth powder, which our author ob- tained by means of folution of the Pulvis anti- monialis in marine acid, was in the fame propor- tion, as nearly as could reafonably be expedted from the nature of the experiments, as that ob- tained from James's Powder. And the part that refifted [ 144 ] refitted folution in this menftruum was partially reducible to a metallic form, and had other wife the fame properties, as far as difcovered, as the infoluble part of James Powder. Dr. Pearfon, having now formed a powder poflefied of properties fimilar in kind to every one of thofe afcertained in James's Powder, with fcarcely any difference in the degree of them, contends, that, if it be thought that among thefe properties are thofe which are effential and pecu- liar ones of James's Powder, the conclufion that thefe two are the fame kind of things rauft be admitted to bejuft. The nature of one of the ingredients of James's Powder, viz. the irredu- cible part of the infoluble matter, he confefTes, is not fully elucidated by his fynthetic experi- ments ; but in fo far as they (how, that this part equally exifts in the powder formed by calcining together antimony and bone, which is conclud- ed to be James's Powder, the objection againft the conclufion with refpect to the identity of the two fubftances, on the ground of this in- confiderable part of James's Powder not being well underftood, muft, he thinks, be of little weight. We come now to the fynthetic experiments which our author made with the view of con- firming L *45 3 . firming or invalidating the conclufiorrs drawn from the above analyfis, with refped: to the in- gredients and proportions of them in James's Powder. From one of thefe experiments (the 3d), which confifted in calcining together equal weights of antimony and hart's-horn (havings, it appears that the calcination of antimony with bone allies is much more fpeedy than when by itfelf; and from another of them (the 5th) we learn what degree of fire is neceflary to render the antimony calcined with bone of a white co- lour; and that this whitenefs does not depend on the air, but on the fire. We (hall here give the whole of this experiment. " (a) 1500 grains of the calcined mixture <c of antimony and bone, Exp. 3. were kept <c red hot in a clo(e veflel for half an hour. On. " cooling, I found the powder changed from et a cineritious or clay colour to a whitilh colour <c with a lhade of yellow- The fides of the cc crucible were not glazed. The pyrometer in ic the middle of the powder had contracted to " 40?. This powder was much inferior in *c whitenefs to James's Powder, being much cc yellower. / " (b) Another parcel of the fame powder, " Exp. 3. was expofed in the fame manner, Vol. III. L. " but L '46 ] " but to a greater degree of fire, in which the tc crucible was almoft white hot for half an hour. te After cooling, the powder was found changed to a loofely cohering, fnow-white, heavy mafs, " and the fides of the crucible were covered " with a yellow glaze. This mafs, which was " eafily detached from the veffel, was found <f covered with a yellow vitreous coat over the ce whole furface of it that had been in contadfc " with the crucible. In the white folid, on " breaking it, many argentine [picula were feen. " The pyrometer tifed in all thefe experiments <c indicated 71?. " (c) 1500 grains of the fame parcel, Exp. 3. were expofed in an open crucible to the fire of a melting furnace ; no fumes arofe till the " crucible began to be almoft white hot. Af- " ter inverting another crucible, with a fmall <*' hole in its bottom, the fumes continued to u afcend at times through the aperture for a " quarter of an hour. The crucible was then te taken out of the fire, and on cooling a whitifh " powder was found, but no glazing, and the '? pyrometer indicated 28?. On 'again expof- u ing this crucible with one inverted over it in u the melting furnace, but to a greater degree " of fire, flill more fumes arofe; but, on cool- " ing, the charge was ftill in the (late of apow- " der, t '47 3 i( der, though whiter than before ; and the in- <s fide of the inverted crucible was covered with <? filvery particles, and the hole of it was fur- u rounded with argentine fpicula, in a flellated ?? form. The pyrometer indicated 39?. On " reducing a little of this powder to a greater ?c degree of finenefs, it was as white as James's ?? powder, with a yellowifh caft like it, but in- ?? lerior in whitenefs to a fpecimen of pulvis " antimonialis. This crucible, containing its 44 charge, with a cover clofely luted on it, was " put again into the fire, which was raifed much " higher than before; and, after being expofed " in it twenty minutes, the powder in the cruci- ble became a loofely cohering folid, as white " as fnow, with a vitreous yellow coat, as be- Sf fore obferved; the infide of the crucible was " glazed and covered with fpicula. The pyro- ec meter-piece in the middle of the powder was tc alfo covered with a yellow coat, but not glaz- " ed, and it indicated 81 ?. This loofely coher- <? ing folid, being pulverized, afforded a whiter '? powder than James's powder. Cd) The crucible, with its charge (b), hav- ?? ing a cover well luted on it, was again put " into the furnace, and the fire raifed to almoft C? as great a degree as I was able. This intenfe La " heat L 148 ] heat was kept up above an hour. After cool - ing, a white hard folid mafs was found with- in the crucible. Oil breaking the veffel, to detach from it the charge, this folid mafs was found as hard as marble, and to have received its figure from the crucible. Its furface was covered with a yellow vitreous coat, and the whole infide of the veffel had a beautiful gold-coloured glaze with many argentine fpicula. The pyrometer piece in the middle of the charge was alfo covered with a fine yellow glaze, and indicated 1660. This folid, hard mafs weighed only twenty-one grains lefs than before the experiment, though the whole infide of the crucible was glazed, and had fhining fpicula upon it. A piece of this hard mafs being pulverized, it afforded a whiter powder than James's pow- der is in general." Our author thinks it will not be difficult, from his, experiments, to give a probable reafon for the James's powder being generally of a yellovv- i(h call, and for different parcels of it, as well as of the pulvis antimonialis, being generally of different degrees of whitenefs and fhades of yel- low. The colour of this preparation is, how- ever, he obferves, a very delicate one. He once [ '49 ] once directed a perfon to calcine together anti- mony and bone {havings, in the ufual manner, to that ftate in which the white powder may be produced by a due degree of fire; but, inftead of a (now-white mafs, he could not by any de- gree of fire obtain any colour but a dirty whitifh or light (tone colour; though repeated calcina- tions were employed. The reafon of the failure ^as, that the earthen difti had been broken dur- ing the calcination, and a few very fmall pieces of it had fcaled dff, and being mixed with the powder occafioned this difappointment with refped to colour. The fame difappointment, it feems, has been alfo occafioned by ufing a rufty iron rod in calcining the mixture. The bone-afhes procured from the fal ammo- niac and fpirit of hart's horn manufactories, fre-. quently failed,' he tells us, in producing a white powder; and fo did fometimes the bone-afhes, called prepared hart's horn, fold by druggifts. Even after a fine white-coloured mafs had been made, if it was pulverized in an iron mortar that had extremely little calx upon its furface, or dirt, the powder was not vvhite. Dr. Pearfon has been told by fome of the perfons who prepare the pulvis antimonialis, that the whiteft colour is obtained by firft boil- L 3 ing [ '5? ] ing the bone fhavings to diflolve their mucilage, and then calcining them with antimony as above lhevvn. Mr. Lile's receipt, he obferves, direfts previous decoction of the hart's horn. He thinks that the yellow coat and glaze on the fides of the crucible and furface of the cal- cined mixture of bone and antimony, which, he obferved in his experiments, fhould be afcrib- ed rather to the fufion of the clay of the cruci- ble with the antimonial calx, than to the grea- ter degree of fire in the part of the crucible in which it takes place; or than to the calx of iron and filiceous earth of the veffel; becaufe the fame yellow coat and glazing are produced on the Wedgwood pyrometer pieces, which are placed in the middle of the charge, and where the degree of heat cannot be fo great as nearer the fide of the crucible, and yet a fnow-white mafs is produced between thefe clay pieces and the fides of the crucible. This yellow coat, he obferves, is one reafon for the powder being of a ihade of yellow in fome fpecimens. From an experiment which he relates, he thinks it very probable, that no degree or dura- tion of fire, applied in open or clofe veffels to antimony alone, can produce a calx of the fame kind as that in James's powder : nor, perhaps, 3 that C 151 ] that fuch a powder can be compofed by fire ap- plied, in clofe veffels, to calx of antimony mix- ed with calcined bone; but if antimony duly calcined be mixed with calcined bone, and ex- pofed to air, in a due degree of fire, for a fuf- ficient length of time, and then a ftill greater degree of fire be applied to it in clofe veffels, fuch a compound, he obferves, may be formed as James's powder. The fame experiment, he thinks, alfo proves, that the fulphur in antimo ' ny is no ways neceffary to the formation of this compound. ' , * Dr. Pearfon concludes his paper with obferv- ing that, from the whole of his analytical ex- periments, it appears: 1. That James's powder confifts of phofpho- ric acid, lime, and antimonial calx; with "a minute quantity of calx of iron, which is to be confidered as an accidental fubftance : 2. That either, thefe three effential ingre- dients are united with each other, forming a tri- ple compound; or, phofphorated lime is com- bined with the antimonial calx, compofing a double compound in the proportion of about fifty-feven parts of calx and forty-three parts of phofphorated lime: L 4 3. That C 1J2 ] 3. That this antimonial calx is different from any other known calx of antimony in feveral of its chemical qualities. About three fourths of it are foluble in marine acid, and afford Alga- roth powder; and the remainder is not foluble in this menftruum, and is apparently vitrified: And from the fynthetic experiments he has related, he thinks, it appears, that by calcining together bone-afhes, that is, phofphorated lime, and antimony in a certain proportion, and after- wards expofing the mixture to a white heat, a compound was formed coniifting of antimonial calx and phofphorated lime, in the fame pro- portion, and pofleffing the fame kind of chemi- cal properties, as James's powder. Befides the preparation, which is more imme- diately the fubjedt of this paper, Dr. Pearfon has examined another medicine fold under the title of " James's powder for horfes, horned cattle, hounds, &c." It is a light clay-colour- ed, gritty, taftelefs ftibftance, in which are feen fmall fpicula; and it appears to him to be nothing more than James's powder for fevers, or Lile's powder, made by calcining antimony and bone- afhes together in open veffels. XV. Ac-