Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/939

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bling, in moft trials, the nitrum of the Levant, which is neither acid nor alcali, but approaching moft to the latter d. — [<= Pref. to Hift. of Plants near Paris. * Medic. Eft. Abr. Vol. I. p. 108.]

Chalybeate waters often break the bottles into which they are put, and many of them foon lofe their chalybeate properties ■when buttled. To prevent the former inconvenience, Dr. Hales put a fmall glafs tube through the cork of the bottles, filling them fo, as to leave no air bubbles between the cork and the water. In other bottles he put very foft comprem- "ble corks. By both thefe means the water was allowed to rarify, without burfting the bottles. By mixing very few drops of an acid, fuch as oil of fulphur, with the Jleel- waters, they long retain their chalybeat properties. See 'Bah, Philofoph/Experiments. Mineral-W at ers. The method of analyfmg mineral-waters, according to Dr. Shaw, fhould be this. Firft, let it be tried what changes they will fufFer by mere {landing ; let fome of the water be put into open glafles, and fume into fuch as are ftopt, and after fome hours keeping, examine by the tafte whether it be any way different from that frefh drawn from the fpring; after this let it ftand fome days or weeks, and finally compare it with (ruth water of the fame fpring, and obferve whether it have any fcum at top, or fc- diment at bottom, or fides of the glaiTes.

2. Let fome of the water be kept in open cylindrical glafles jn a warm place till it is wholly evaporated, the dry fub- ftance left behind muft be carefully preferved, to be com- pared with the refiduum to be afterwards made by fire.

3. Put a quantity of the water at the fpring-head into a glafs retort, and a receiver being luted on, let the whole be carefully diftilled over, and both the water and the dry re- fiduum weighed, and carefully preferved. If during this operation a vapour is feen to force its way out at the joints, It (hews there is a fpirit, or light fubtile matter. In the water too fine to be feparatcd this way, the water feparated .by diftillation is to be tried feveral ways, to fee whether it differs from common dillilled water or not, and whether it have the fame mineral particles that the water itfelf had be- fore diftillation. If it contains any fea fait, it will turn white with a folution of filver; if any vitriol of iron, it will turn black with powdered galls ; and if any fulphur united with an alkaline fait, it will turn black in time with any of the

.metallic folutions. The dry matter left in the retort is to be boiled in fix times its own weight of pure diftilled water, this being afterwards filtered and ret to cryftallize, will give, after a proper evaporation, its own peculiar fait in cryftals ; and if more forts of fait than one fhould be contained in the water, they will be all thus feparated by repeated evapo- rations and cryftallizations.

Whether thefe falts be acids or alkalis, is eafily found by the common experiments, the acid turning fyrup of violets led, and the alkali turning a folution of corrofive fublimate yellow. The neutral falts, w.ifhed out of the earth by waters, are chiefly fea fait, and fuch as confift of a vitriolic fait, and a fait or earth of an alkaline nature. Sea fait is dif- . covered by its tafte, by the white fume it yields on being mixed with oil of vitriol, and by its figure in cryftallizati- on : and the other neutral falts are difcovered by their pro- perty of producing, or regenerating fulphur, upon being mixed and melted with fait of tartar and powdered charcoal. Thus, if two ounces of fuch fait be mixed with one ounce of fait of tartar, and an ounce of powdered charcoal, and the whole put into a crucible, there will be produced a red- difh-coloured mafs of a fulphureous alkaline tafte, and giv- ing a high yellow colour to fpirit of wine, which will turn filver black ; and being precipitated by an acid affords a true lac fulphuris, which may be fublimed,.and melted into brim- ftone like the common.

What remains of the refiduum, after water has feparated the fait, is properly earth : this is often of more kinds than one, and may be feparated by repeated wafhings into-' bole, ochre, fand, and whatever elfe it corififts of ; and thefe may afterwards be tried, as to their nature, by fire in the com- mon ways, the firft and readieft of which is the feeing whe- .ther they will calcine or vitrify; and the next, with proper additions, to try whether they contain any metalline or mi- neral particles, which may be feparable by the feveral fluxes : and if the quantity of metalline matter be too fmall to be collected into a regulus, or {hew itfelf in the common way, it may be melted with chryftalline glafs, and from the colour it gives that glafe, the metal it contains may be known. It is generally fuppofed, that the mineral-waters receive their virtue from the falts they contain. Dr. Lifter is of opinion that thefe are principally two, the one common fea fait, and the other the nitrum calcarium ; and found, on experiment, that from thofe very waters, which others had boldly af- firmed contained nitre of the common kind, vitriol, alum, and the reft, he only could feparate thefe two falts. Thefe falts mixed with ochres make the various kinds of our mineral-waters, as they happen to be mixed in various proportions.

Monfieur Du Clos obferves of the examining the virtues of mineral-water, that moft of them are liable to great errors.'

The French Academy, after long deliberation, proposed to themfelves a method of examining the waters of their owri country, by which they arrived at a more thorough know-* ledge of their virtues than was had before, and which may ferve as a leflbn to all other experimenters in the lame way. , They have found by all their enquiries, that the principal things giving virtues to waters are falts and earths, and thefe give very different qualities to them, as they differ in quan- tity or in quality in the feveral (prings. The falts, which they procured by a flow evaporation or diftillation, prqved to be of two kinds : the one the nitre of the antients, 2 fulphureous mineral fait, much refembling the alkali of plants; the other the common culinary fait. This canfiits of two parts, an alkaline bafis and an acid. Thefe two prin- ciples are fometimes combined in the waters, and then it is abfolute fait that they contain, and eafily feparated and known : but it fometimes alfo happens, that thefe principles are feparated, and only the one or the other contained in 2 water ; thefe therefore, when procured in the analyfis, are not eafily known, and when they are, as it very often hap- pens, blended with the difunited principles of other falts, they form together a fort of concretes, yet more hard to be known than the other. It is generally fuppofed, that in almoft all medicinal waters there is either alum or vi- triol ; but this is an opinion taken up too much at random^ and it appeared, on the examination of all the mineral fprings of France, that no one of them contained either the one or the other of thefe falts, except that of Vahls iri Dauphine, which contained a fait fomewhat refembling white vitriol. The tafte and the mixture with acids, alkalis, and tinctures of vegetables, are the great means of knowing thefe falts ; for as to their figures they vary greatly, even in the fame portion of fait, according to the different degree of the evaporation of the water they were difiblved in. Dit Clos, Exam, des Eaux Min.

Earths are found in different quantities in the different waters, and fo con fu fed by being blended with one another," and with other foflils, that it is much more difficult to af- certain their fpecies, than thofe of earths in any other form,' or than thofe of the falts in the fame waters. The colours of the earths are very various, but this is the Ieaft variety ; for fome of them form themfelves into fhapes and appear- ances fo different from the others, that it is hard to fay what they are like, or to what fuch fingularities in their concretions fhould be attributed. Some float about in the almoft evaporated water in form of films and clouds, fome . like flocks, fome appear in the form of mucilages, others' like little flaccid clods of clay, and others like grains of fand % fome are foluble in acids, fome only in part foluble, and fome not at all fo ; fome will give a tincture to diftilled vi- negar, others not; and in the fire fome run to glafs, and others calcine to lime.

The great quantity of the mineral-waters, which phyficians ufually prefcribe to be taken by thofe they recommend theni to, feenis to prove that they expect the principal benefit from them by their cleanfing the vifcera by this internal ab- lution ; and this effect is indeed no trifling one, finee moft of thofe ftubborn difeafes, which they recommend thefe waters in, are owing to obftrudtions of the vifcera, which' the large quantities of thefe waters may ealil'y remove : but it were well, if the phyficians would be more accurate in di- ftino-uifhing the different properties of them, and not give them at random, as is too often done, to the no fmall de- triment of the patient.

The vinous fharp tafte of fome of thefe tvaters which eva- porate with the leaft heat, or on being expofed to the air,' feems to be owing to that matter which is the firft ftate or being of fulphur, and of all the concretion's thence re- taking; fuch as the various vitriols, and the like. There are found earths impregnated with this acid volatile ful- phureous matter, of the concretions of which are fome- times made fulphureous and vitriolic minerals. This vapo- rous and indigefted matter may very well be the bans of vitriol; but in this its firft ftate it cannot be a vitriolic con- cretion, if it be found in earths where there is yet no vi- triol. It is more eafy to obferve it in its products, when it has received fome mineral concretion, than in its natural ftate; though in this latter ftate it is as likely to impregnate waters as in any other. The moft probable opinion, as to' the heat of thefe waters, is, that there are in certain deep receffes of the earth hot vapours, which continue at all' times fo, becaufe there is no accefs of the external air to cool them ; and where thofe rarificd matters have not room' to become more rarificd, and fo to become lefs hot, or more diffipated ; and that fuch collections of hot vappurs are what give heat to the warm baths, and Hot jnedicinaf- waters. Du Clos, Exam, dc les Eaux Min. Many mineral-waters evidently contain a large quantity of fpar, which though fufpended in them in an abfolutely pel- lucid ftate, may yet be regularly feparated from them by evaporation in its own figure. The waters of the fountain' de Salut, and thofe of the fpring du lied, and feveral other in Gafcony, have been tried, and are found, if gradually evaporated to a- certain degree,- to yield a fcum,which, when- examined