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Isti Arsenic, the most virulent of metallic polsons, has longbeen employed medicinalty With success, but is now for thefirst time introduced in to the Pharmacopoeia. The probableabuse of any medicine affords no argument against iis use, is it did, opium, oXymuriat os mercury, and many of our most potent articles, might be excluded Dom the list of Materia Medica. But where the smallest error may be attended by haZard, caution cannot be too osten or too forcibly impressed; nor is an error in any given dose the only source of ha Zard, sor misclites may follow iis too long continuance in doses, Whicli, separalely taken, are insufficient to produce distur, ance ; in the former instance, it may destroy life with ali iis peculiar violence of symptonas, in the lalter, it may, in sonae constitutions, produce tremor or paralytic affections, so that iis administration ought to be carefulty Walched; is it he, iis P ΟWers as a medicine are mari ed and useful, and the College, by iis introduction, have hoped rather to obviate those abundant evils whicli follow iis irregular Use as a Secret medicine This preparation depends upon the union of the oxyd with potass, and the solubili ty of the neW compota nil in Water, whicli forins, is the nomenclature of FOUrcroy be adopted, an Arsenite os potass. It is, aecording to the formula of the late Dr. Fowler, of Stafford, who sirst introduced it, in imitation os a celebrated popular remedy for intermittents sold under the nam e of Tasieless Ague Drops, and whose preparation is in established use. The compotand sp rit oflavender is only intended to give sonae colour and taste, Without whicti it would look like common Water, and heiacebe more liable to mistahes. Where the dose is smali and the effecis so poWerfui, the most minute attention to iis Proportion and preparation hecome necessary. Each fluidounce
contains four gratias of the oxyd, and each fluidrachm half a gratia, but it Wili seldona be proper to go beyond ten mininisas a dose for an adult. It should se em that for the purpose
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of such an accurate division, nothing could be more ciearthan the intention and expression of the directions, that siXty-Dur gratias of the oxyd os arsenic should be contained in ariexaci pint of liquid, and that the addition os distilled wator, When necessary, is Only to secure this essentiai potnt.
Another modification os arsenic, consisting of the metallic base united to a stili larger proportion os oxygen, and thencalled by Fourcroy, Arsenic acid, has also been used in medicine, combined With potass, under the nam e of Macquer's arsenical sali. It is usualty formed by heating in a crucibi eo quat paris of nitre and White oxyd os arsenic, as long as any nitrous gas comes Over ; then dissolving the mass in Water, and crystalliZing the sali by evaporation. . The fame sali has also been formed by uniting the arsenic acid previolasty prepared, with the aikali. As the management of the heatis a circumstance of Some nicety, and as uraequalty applied, it may produce uncertain ty in the result; the present preparation, Whicli has also the advantage of pretiy extensive experion e in iis favour, has been adopted. Such a preparation is introduced into the Dublin Pharmacopoeia.
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Rub them togethor in a glass mortar untii the mixture Censes to effervesce, then drythe ammonia ted Copper, Wrapped in bibu-lous paper, in a gentie heat.
Tliis preparation is noW frst introduced into ille Pharmacopoeia, and the process, whicli is that also of the Edin- burgii college, and sufficiently correct for medicat purposes, is employed instead of any more eXpensive methods by precipitation. There is sussicient Water of crystalligation in thes ait to render the compound moist, but the action and the eL
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fervescence are but stigiis, and are more correctly, perhapλjud ged by the ear than by the eye. It requires to be driel ery gently, for increase of heat Wili delach a portion of the ammonia; and as it is so readily prepared, it is beller that smali quantities only should be made at a time. Ιts ricli darlablue colour and ammonial smeli are the tests of iis good-ness. Ιis chemicat composition has not been correctly aScertained ; probably it is a subsulphat of copper and ammonia. The term ammoniarum is used not as explaining the composition of the substance whicli is not a mere compound of Ammonia and Copper moniaretum Cupri , but as avolding amore ProtiX name, and ansWering every purpose of designation without leading into error; the Same observation almapplies to Ferrum ammoniallam.
Aqua cupri ammoni uti, P. L. I 787. Aqua Sappharina, P. L. II 15. P. L. II 20.
Tahe of Ammonia ted Copper, a drachm. Distilled Water, a Pint. Dissolve the ammonia ted Copper in the water, and si iter the Solution through paper.
This was prepared in the Pharmacopoeia os II 87 by mixinglime and muriate of ammonia in Water, and letting the miX- ture Stand in a copper vesset. Ιf the Ammonialed Copperbe neWly prepared tiae solution is complete, and the liquor tranSparent; at least, I have Seen only a very slight turbidityat the bottom of the botile aster it has stood thr gh a day,
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Ferrum ammoniacale, P. L. II87. Flores martiales, P. L. 1745. Ens veneris, Ρ. L. II 20.
The original base os this preparation was in. Boyle's ms Veneris, but doubis were entertained as to the fori os vitrici he employed, Whether green or blue, Whicli his descriptionos the process by no means clears up. Μetallic iron Was directed in the Pharmacopoeia of 1787, but be re it could de- compose the muriate os ammonia it required to be Oxydated, and this was imperfectly dono by the decomposition of themater contained in that sali. The process is there re Shorten-ed, and one sublimation rendered sussicient by the usa of iron
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already in iis state of oxyd, and by modi*ing the directions
for the regulation of the sire. Intimate admixture of the two Substances, and eXPOSUre at Once to a Strong heat, arenecessary ; for it is only in high temperatures that oxyd of ironwill decompose any of the muriate os ammonia, and lowerones will sublime away that sali unaltere l. As great heais cannot weli be desined or correctly regulated, I have doubted whether this and many other metallic preparations, dependant Upon temperature, might not other Wise be prepared more uniformiy; as for instance, is a given proportionos tinctura ferri muriati Was added to a solution os muriate Os ammonia, and the miXture evaporated to dryness. The more intense the heat and the quicher the sublimation, thegreater proportion of iron Will the sublimate contain, and this difference is evident in the variations of itS colour, aScollected in different paris of the necla of the retort. It consists of red muriate of iron, united by sublimation with muriate os ammonia, anil, as the subcarbonate of iron contains a portion os carbonic acid, miXed also With some carbonate ofammonia. It is orange-coloured, With a smeli resemblingsasfron; is deliquescent, and solubie in alkohol. The residue, whicli is deliquescent, consists also of red muriate of iron, and was formerly hept under the name of lixivium martis
Ferri rubigo, P. L. I 787. Chalybis rubigo praeparata, P. L.
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Dissolve the sulphate of iron and subca1 honate of soda separalely, each in four pinis of Water: nexi mi X the Solution S together, and
set it by, that the precipitaled poWder may
subside: then having po ured olf the Supernatant liquor, Wash the Carbo nate of iron Withhot water, and dry it upon bibulo us paper ina gentie heat.
There are two oxyds of Iron, both of whicli are combin- le with aci is and form disserent modificatioris of the fame sali, a distinction whicli requires to be especialty attended toin medicine; they have been named frona their colour, blacla anu red oxyds, and also more Properly to eXPreSS the Proportions os oxygen, protoxyd and perOxyd; the former, whichis blach, or is formed as in the present instance by precipitation Dom mater) greenisti, conSisis of iron . 73, oXygen . 27, according to Lavolsier. It may be formed by Various methodsias hy exposure os a paste of iron silings and water to the air ;by heating together one part of red oxyd of iron and two paris iron filings; and by ad ling a solution os aikali to oneos green sulphate of iron, and drying the precipitate quicElywithout exposure to air: and it is hept as a separate article in the Edinburgh Pharmacopoeia, Under the name of Ferrioxydum nigrum purificatum. The lalter, or red ΟXyd, consisis, according to Proust, of iron . 52, oxygen .48, and in iis relation to blach oxyd is composed of 66,5 of that oxyd, and 23,5 of additional oxygen . Some Chemisis have supposed the existence of other gradations os combination of iron and OXygeia, but the above are ali that are generalty admitted, orrequire to be noticed here ; this laiter is also Lept in the
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Edilaburgh Pharmacopoeia, under the name of OXydum ferri rubrum, and is intended to be in that state of Oxydationto whicli the metat is to be brought by the present preparation. Salis containing the black oxyd, on exposure toair, pas8 to the state of red oxyd, by attracting oxygen Domit, and in the process os drying the sanae change happens hereto the oXyd in the subcarbonate, Whicli at the time os iis first precipitation is a blach oxyd. The fame Substance, more imperfectly prepared, by the expostare of iron si lings toair and water, constituted the rust of iron ferri rubigo9 of the former Pharmacopoeia, for Whicli, in ali the processes intowhicli it entered, this precipitate is no substituted. Thered oxyd of the Edinburgii College, is the old Colcothar
vitrioli, and formed by exposure os common sulphate of ironto a strong heat, sum cient to drive over iis sulphuric acid, when the recl oxyd remains bellind, as in the process Whichwas formerly in use for obtaining that acid. Carbonic acidholds iron in solution in low temperatures as in many minerat waters, Whicli is precipitaled When it is driven OT by higherones. Temperature thereos influences eastly the quantity of the acid contained in the preparation; but the directions given in the texi Will supply a substance sussiciently uniform and correct for eVery purpose of medicine. Subcarbonate of Soda is preferred for the precipitation to that os potass, On account of the greater solubility of the sulphate of the former than of the lalter athali, and the Consequent fa
now directed is tess than in the former edition.
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Ferrum vitriolatum, P. L. I 87. Sal martis, P. L. II 5. Sal seu Vitriolum martis, P. L. 172O.
Sulphuric Acid, of cach by Weight
This sali is sermed upon the large scale Dom native sulphuret of iron nrites , by moistening, and exposing it to theopen air. The sulphate of iron is asterWards dissolved in Water and crystalliged by evaporation ; but, in order to Ob-tain an uniform and pure sali, iis preparation is here directedas a process of pharmacy. Sulphurio acid Will unite either With the blach or red oxyd ; the first of these is the sali here intended sor internal use, and upon this poliat great stress
ought to be laid, as the last is the state in Which the sulphateos trade is usualty found, and whicli, for medicat purposes,
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is a very distinci and probably inferior thing. Iis crystals aretransparent rhomboidal prisms, of a light green colour ; iistaste is astringent and strong, and it reddens vegetable blues. One part is solubie in two of cold, and in three- urtiis of boiling water. It is insolubie in athohol, in Whicli menstruum the red sulphate is solubie, and this affords a mode ofascertaining the existence of the lalter With the former, asalso os separating it. On eXposure to air it is gradually converted into red sulphate: it consisis, according to IcirWan, of acid .26, iron .28, water . 46. Heat drives off the wateros crystallization, and the sali rematiis White; is urged farther,it drives over the acid, and leaves sirst a red sulphate, and atlast a red oxyd of iron.
Ferrum tartarietatum, P. L. 1787.
Rub them together and ex pose them to thea ir in a broad glaSs ve88el for eight days, then dry the residue in a sand bath, and reduce it to a very sine poWder. Add to this PO der a Pint more of Water, and ex pose it