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fiticr that iron is always found in the aftiss of vegetables, and that it, therefore, evidently attends in extremely minute particles, with the juices of plants ; and that fal armoniac is prepared from a foot made of the excrements of thofe animals which feed on plants, we iball find it no impoffi- bility that iron mould be there; and we well Know that iron, in any ftate, cannot but give that colour to glafs, which nitre* in a fmaller quantity, and fal armoniac, in a larger, are able alio to give. Memoirs Acad, bcienc. Paris.
1736.
All obfervations and experiments would feem to prove that the red colour given to glafs by nitre, can only be owing to ferrugineous, or ammoniacal matter contained in it; and it is no very rafh conjecture, to fuppofe that the ammoniacal matter contained in the falt-pctre, rarifying, and extremely dividing the ferrugineous matter, during the time of the dii'iil- lation, may distribute them in their disjunct molecular, to all that matter, or thofe particles, which form thofe vapours, and tinge them red by its diftribution of them. It is to be obferved, however, that the vapour offpirit of 'nitre, or of aqua fortis, arc not always red, but only are fo when the fire is great enough to raife with the vapours the matter which colours them; for if fpirit of nitre be made with the addition of alum calcined, with dry falt-petre, and with filings of zink mixed together, there will be obtained with a fmall degree of fire, a fpirit of nitre, which does not come, over in red fumes.
If the fire be raifed to a greater degree of violence, there will afterwards be obtained a fecond fpirit of nitre, which will come over in red fumes ; but the firft of thtfe will {View the great experiment of talcing fire on mixture with oil of tur- pentine, or the European oils of vegetables, better and more readily than the other.
It is therefore no efTential character of fpirit of nitre to rife in red vapours, fince the firft rifes without; and this is truly the pure fpirit of nitre % while the fecond, which rifes in red fumes, is impure, being coloured by ferrugineous, or other foreign matter raifed in vapour with the reft, by the great vio- lence of the heat.
It is ohfervablc, that if vitriol calcined to a rednefs be ufed with the nitre, for drawing the fpirit, the vapours rife of a perfect blood red. In the common way of diftilling what is cailed fimply fpirit of nitre, the cuftom is to put into the retort with the falt-petre, a very large quantity of a vitriolic earth ; and in the making that fpirit called aqua fortis, green vitriol, or EnMifb copperas is mixed with the nitre. This is abundantly known to contain a great deal of iron. Here, therefore, is in each cafe a quantity of ferrugineous matter added; and we well know that this can give a red colour to the vapours, with which it is by violence of fire compelled to rife. Repeated trials of fpirit of nitre, with mercurial preparations alfo, prove beyond contradiction, that there is ferrugineous matter in that fpirit. Many of the common mercurial precipitates, when made with aqua fortis, or with plain fpirit of nitre, may have abfolute plain iron feparated from them ; and the cbemifts know well that this is not to be fuppofed to have been lodged in the mercury, fince it is very difficult to conceive how that metal fhould become amalgamated with it; but there can be no diffi- culty of fuppofing it feparated from the menuruum, fince it is "evident that there is iron contained in the matters ufed in the diftillacionof it, and even in the fait itfelf from which it is originally drawn.
It would be very natural to fuppofe that the ferrugineous matter was raifed only from the additions of pure vitriol, or a vitriolic earth ; but it is evident from the experiment of nitre alone turning glafs red, that there is certainly alfo ferrugineous matter in that fait itfelf; nor is it at all difficult to conceive how iron comes to enter the hody of that fait ; fince, if we confider it as made in Europe, from the rubbifn of old build- ings, and the cleanfings of {table?, &c. it is eafy to conceive that pieces of iron of feveral kinds may have been rafted away, and confirmed there, and fo mixed among the matter from which the fait was afterwards made. The addition of wood afli.es always ufed alfo in the making it, may have lodged ferrugineous matter among it, fince it has been often proved that the allies of all vegetables contain true iron. Memoirs Acad. Scienc. Par- 173°-
It may feem a difficult thing to conceive, however, in what manner fo fmall a qu mtity of iron as there can be fuppofed to be in nitre, is able to colour fo large a body of vapours as are km to rife in the diftillation. But if we confider the extreme divifibility of the particles of metals into colouring matter, and the vafl quantity of water that a fingle grain of copper is capable of tinging blue, when dtflolved in an alkali, we fliall be the Iefs furprifed at it; efpecially if it be confidcred alfo that it has been proved already that there is true fal armoniac in all nitre, and it is well known that this fait is capable of rarify- ing, and extremely dividing the particles of that, or my other metal ; and if as much fal armoniac as can be diuolved in aqua fortis be added to that fpirit, it is well known alfo that it will make it feivf up vapours much redder than before, which can only be owing to the fal armoniac railing a larger quantity than ordinary of the ferrugineous matter contained
in the aqua fortis than would naturally have been raifed from if. The moft ready way of reducing litre to powder, is to dif- folve a quantity of it in as little water as may be, and eva- porate the water over a gentle fire, continually ftirring it till dry, by which means the nitre will be found in form of a very dry white powder. This is the method ufed by the gun- powder-makers. Shaw's Lectures, p. -389. The curious, in the hiftory of nitre, and its preparation from vegetables, &c. and the purifying it for gunpowder, and other ufes, may confult the works of Glauber, StahJ, and Clark, on the fubject of this fait, and compare them with the difcourfe of the younger Lemery on the origin of nitre. Purified Ni trf, See NiTT.uM purificalum. Spi* it of 'Nit'je. See Spiritus nitri
NITRIUV1 fal, in natural hiftory, a name given by many wri- ters to the fait feparated from the water of the lake Natron in ./Egypt, which is the natr-um, or nitre of the antients. This lake is fituated in the Nitrian defart, fo called from Ni~ tria, a very large town there It is fix or feven acres in ex- tent, and lies about thirty miles weft and by fouth from Tc- rana, and about the fame diflance north from the pyramids : from the bottom of this lake the fait called nahum arifes to the furface of the water, and is there condenfed,1jy the heat of the fun, into the hard and dry form in which it is fold. Eour ounces of the water of the N.:tron being examined by evaporation in a glafs veiTel, placed in a fand heat, there will arife, as foon as it becomes warm, a fort of fcum to the top ; this being taken off, another inftantly fucceeds, and fo on, fo long as any water remains in the glafs.
This fait, thus feummed off, is the fame in all refpects with the natram, or the Smyrna foap earth; beino- a fixed alkali, fermenting with acids, and boiling into foap with oil. This icy fcum is the fame as that called by Pliny fios fa;is, and feems to be the fame with that which Herodotus fays the /Egyptians made ufe of in the preparation of their mummies. It is laid that the water of this lake, though it contains ever fo large a quantity of this fait, will not ferment with any acids, tho' the lea- particle of the fait feparated either by a natural, or artificial heat, will ferment violently with any acid. What the' heat of'the fand furnace does in this experiment, the heat of the fun does in the lake itfelf ; and the fmgular circum- ■ fiance of the water of the lake not fermenting with acids, is confirmed by this, that a clear folution of die fait in com- mon water will not ferment with them.
The antients have attributed great virtues to the fait of this lake ; and this being called nitrum, as a fliort name for nitr't- urn fal, we have had fome who have fuppofed the fait which we call nitre, to be the fame, and thefe people have wonder- ed that they did not find the fame virtues in our nitre. The mineral waters of all parts of the world feem to con- tain more or lefs of tins fait, and to owe their virtues in a great degree to it ; and, probably, it might be no fmall improvement to phyfic, to bring it more into the prefent practice. Molenbroch recommends it greatly in the fione ; and it may be the more probably ufed, as all alkali falts are known to be good in that diftemper. Some add to this, that tt feems qualified to diffolve ftony fubftances, it being of fo piercing and penetrating a fpirit, that no rock, or ftone is found about the Like from the waters of which it is pro- cured. Phil. Tranf. N° ibo, NITRO/'iERiALy/'n-//, a term invented by Mayow; and fince ufed by many others, to exprefs a very active principle in the air, caufing great changes in the bodies abforbine it and ex- pofed to it.
The acid fpirit of nitre is produced partly by the air, and partly by a terreflrial matter making up the reft of the hody of that fait. Mr. Boyle, in his experiments on flame and air, has abundantly proved this; and that igneous particles of the air refide in nitre, is as certain a conchifion from the fame prin- ciples : thefe conftitute its moft active part, and by thefe the flame of kindled nitre is produced.
The aerial particles of nitre are truly no other than the i»neo- aerial matter of it, and this aerial matter is evidently lodged in the acid fpirit of it, not in the fixed fait. This acid fpirit i?, according to Mayow, cempofed of a terrene matter, which is- flexile and humid, and of etherial particles, which are rigid ^and dry, active and igneous, and proceeding from the air. Thefe igneous particles are common to nitre and to air, and are therefore called mtroacrial ; and the fpirit of nitre derives, according to this fyftem, from thefe particles its active and corrofive quality, which makes it a fort of potential fire ; and on this the form of nitre chiefly, if not only depends. Now as this nitroairial or igneous fpirit reiides in the acid fpirit of nitre, it is thence inferred, that the niiroaeriai fpirit is of a nitro-faline nature, obtaining rather the nature of an acid than a fixed fait ; confidering alio, that the cffecVs of fire in general anfwer to thofe of a very fubtle and corrofive fait. Eire in general, on thefe principles, is eafily proved to depend principally upon the faid nkro-airial principle put into motion.
This nitro aerial fpirit makes the moft active, and, indeed, the principal part of the fait which we call nitre Its terreftrial and acid parts make up the reft of the mafs \ and thefe are rather of
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