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water, as there was mineral water, in a glafs, exactly like that made ufe of in the preceding trial. Drop in the folu- tion of fteel cautioufly, till the colour is the fame with that of the mineral water. By this means, the due proportion of the folution to imitate any Jleel-zvater may be known. He has thus made fpring water fo like to feveral chalybeate waters, that none could diftinguifh them. Med.EfT. Edin. Vol.I. p. 126.
Galls in tin&ure are more convenient than in fubftance'for making thefe experiments, for it ads much fooner, and more equally, and can be added in lefs quantities, which deferves to be regarded ; for too large a proportion of galls poured ■at once mto fteel-waters, will be fo far from ftriking the co- lour Wronger or fooner, that no change will happen for fe- veral hours after, and at laft the water gradually becomes of & deep fca-green colour, inftead of a purple or violet. Good thaiybeatc waters may have been condemned as containing no iron, or as being impregnated with copper, from an ad- dition of too much galls. "Frefh tindlure of galls is prefe- rable to that which has been long kept ; but even fuch as was grown mouldy, and had a thick fediment, anfwered the common trials. Frequent trials mould be made, at diffe- rent times, with water bottled at different feafons, in order to afcerta'm the proper feafons for bottling mineral zvaters, and to find out the time each will keep. It is alfo requifite to obferve what time it is before the galls ftrike the full co- lour, and how long it remains in an open glafs ; for Mr. Geoffroy's fuppofition appears rcafonable, that both thefe effe&s will be moft flowiy produced, when the fteel is moft intimately blended with the other principles of the water. Med. Efl". Edinb. Vol. I. p. 127.
There isa ftrong refemblance between our fteel-waters and common water, in which fal martis is dhTolved, but the na- tural fpaw expofed to the air foon lofes its chalybeate tafte, and will not ftrike a purple colour with galls ; expofed to heat its virtues are fooner loft, and it becomes vapid in no long time in the clofeft veffels ; but a folution of fal martis bears heat, and being expofed to the air, without alteration ; it may be fufpedted that this difference depends upon the frhall proportion of the vitriolic principles, and fome change they may thereby undergo in the water ; and therefore Mr. Monro having added as much fal martis to fome bottles of water, as had been found to make it of the fame tafte, and to ftrike the fame colour with chalybeate waters, he corked fome carefully, others lefs carefully, and a third fort he left Open. The water in thefe laft loft its tafte and virtues in a fortnight, became muddy, and had a faffron-coloured powder at the bottom. The fecond kind kept longer, but had a 'ftinking fmell before it became vapid. The water which was carefully corked and rofmed kept well, but acquired a ftrong fmell of rotten eggs, like to what feveral fpaws have when kept ; when the bottle was left open, the ftinking fmell went off; foon after, the chalybeate virtues were not to be obferved, and the bottom of the bottle was covered with the faffron-coloured powder, which is generally to be feen in bottles where chalybeate waters have been kept. The difference therefore between the natural and artificial y?^/- waters confifts in the greater volatility of the former. Med. Eft". Edinb. Vol. I. p. ia8.
Spaw and Pyrmont, and fome of our own chalybeate waters, feem an exception to the refemblance between the diluted folution of fait of fteel and the natural fteel- waters ; for the colours they ftrike with the galls is faint, while their tafte and other .effects are ftrong. This produced another expe- riment to imitate them, by mixing filings of iron, oil of vitriol, and water, in a Florence flafk, which being laid on its fide, and another, in which was fome fountain water, immediately fitted to it. The fumes which arofe upon the effervefcence of the oil of vitriol with the fteel, came over into this. After the effervefcence was over, on taking away the glafs with the water t it was found limpid, but with a ftrong ernpyreumatic fmell ; its tafte at firft was pungent, and then the acidulous tafte prevailed. When tindfure of galls was mixed with it, it became of a purple, but faint colour, which held many days without precipitation. Next ■ morning the empyreuma was gone, and the water had an agreeable fpaw tafte. In lefs than a day this went off, a fmall quantity of faffron-coloured powder fell to the bottom, and the galls had no effec-t on the water. Med. Efl". Edinb. Vol.I. p. 129.
This water gives no fign of acidity, as might be fufpected, •when mixed with fyrup of violets and clove-july-flowers, in the colour of which it makes no alteration ; neither do the more fpirituous fpaws ; whereas the folution of fait of fteel, and fome fpaws, appear alkaline, from changing the colour of botli the fyrups green.
The fuccefs of this experiment produced fome others, to difcover what it was that evaporated, and what precipitated in thefe zvaters. Oil of vitriol poured on the faffron-coloured refiduum made no effervefcence ; upon the addition of a little water, fome of the powder feemed to be diffolved. Tinc- ture of galls did not change the colour, but upon adding fpirit of hartfhorn, a great effervefcence arofe, and a deep purple coagulum was made. The fame experiments fucceed with ruft of iron, which refembles this powder. Neither
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ruft, nor the powder, when fufpended |in water, ftrike any colour with galls, although crocus martis does. What eva- porates is the menftruum, which carries away fome of the principles of the iron with it. From feeing the effects of acid, and of the air upon iron, and finding vitriol naturally formed, it may reafonably be fuppofed, that the menftruum of the irony particles in thefe waters is an acid. From con- fideringhow much fulphur is in iron, what a ftinking fmell mineral waters have before they turn vapid, and how much the fulphur of iron is deftroyed before the iron turns into ruft, which again refembles the powder precipitated in thefe waters, we may fairly fuppofe that the menftruum carries the fulphur along with it, and leaves only the earthy parts with a fmall proportion of fulphur. Med. Efl*. Edinb. Vol. L p. 130.
It may hence be fufpedted, thatfteel-zvafers&re impregnated with common grofs vitriol, or with the more fubtile fumes of iron diffolved in the natural menftruum; or with both in different proportions. The quicker precipitation, and lefs volatility of chalybeate waters, feems to fhew that the fulphur is not fo much freed from the earthy particles, as in others which precipitate more flowiy, and are more volatile. The common obfervation ot air generated in all effervefcen- ces, fermentations, putrefactions, and wherever a confider- able change is produced in the compofition of bodies, feems to account for the quantity of elaftic air, obferved in chaly- beate waters, in the more fpirituous when recent, and -in others, when the putrid fmell fhews the fulphur to be more difengaged.
It feems alfo, that the different kinds of fteel-waters mould be prefcribed, according as there is occafion for a fubtile, penerrating fulphureous fpirit, to pervade the fmalleft veflels, or according to the quantity of an abforbent aftringent earth, which is required to be joined with this fpirit. Where different fpaws are not to be had, the- fame water perhaps may be made to anfwer each of thefe intentions, according to its being more or lefs kept, or expofed to the air or heat. Med. Eft". Abr. Vol. I. p. 131. The ingenious author, from whom thefe obfervations and conje&urcs have been taken, feems to think that the -men- ftruum really flies oft" from mineral waters; but this, as is obferved in a note added by his learned abridger % has not yet been made appear by any fatisfadtory experiments. It is certain, that fome mineral waters, when carefully bottled at the well-head, and oiled at top, after the manner of Flo- rence wine, and then well corked and cemented, have been found to continue many months poffeffed of their proper- ties of ftriking black or purple with galls ; and hence it ap- pears that the irony particles, or mineral fpirit of the wate?; cannot eafily efcape through the pores of glafs ; at leaft not while the water remains in a found ftate. When the water begins to corrupt, as in time it will, though thus fecured, it tinges iefs and lefs with galls, and at length affords no red, purple, or dufky colour therewith. Whence we are led to conclude, that the irony particles make their efcape through the pores of the glafs, or of the oil, the cork and cement; or elfe are fo changed, as no longer to retain their irony nature, and ftrike with galls. But that the latter feems rather to be the truth of the cafe, is fupportcd by this, that during the diminution of the tinging faculty, there appears to be a mnnifeft change in the natural texture of the water ; for a vifible feparation of parts enfues, the whole grows fetid, a grofs matter falls to the bottom, the oil that was liquid before, now becomes almoft as hard as tallow, and appears tinged black to a confiderable height: but what is remarkable, the water now affords manifeft figns of its containing a&ual brimftone, not the leaft indication whereof appeared before. It feems therefore that the water, as taken from the well, is a compound liquor, gradually tending to an alteration in its parts, as if there was a flow fermentati- on among them, whereby the natural texture of the whole is broke in time, even though the external air be kept from communicating therewith ; but if external air be admitted, remarkable changes muft fooner begin, and finifb their pe- riod b . — [ a Ibid. p. 130. b Sbaiv's Enq. into Scarb. Wat. p. 160, feq.]
There is commonly fuppofed to be fomething fo very vola- tile in many jleel-watcrs, as well as of thofe of Liege and Pyrmont, that itdifappears upon the leaft accefs of air, after- they are taken up from the well, efpecially in hot weather j. yet it does not fcem clear from experiments, that the alte- terations which fpaw waters undergo, by being expofed to the air, is owing to the diffipation of any volatile part. Ibid, p. 109, and note *.
Though chalybeate zvaters are commonly fuppofed to contain vitriol, and to be of a ferruginous nature, and have from thence obtained their name, yet it is not eafy to determine what falts they contain, or whether they be all impregnated with the fame kind of falts. Mr. Du CIos could neither find alum nor vitriol in any of the French wells, only in one he found fome refemblance of the latter. All the other wells gave a fait, anfwering-to a compofition of nitre and fea fait mixed in various proportions, which probably is the natural fait of the earth difcovered by Tournefort c , refem- 3. bling,
