WAT

WAT

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almoft the only metal ever met with. Wherethe iron is in very minute quantity, and thewater fomewhat acidulous, this tell does notalways produce a precipitate but only a flightreddening ; but its action is much aflifted byprevioully adding a few drops of any alkalinefolution. The pure gallic acid, or the tin&ure ,or.the infufion of galls, a£l nearly- equally well.Sometimes minute quantities of iron are welldetected by fufpending in the water a piece ofdie gall-nut for fome hours.

11. Prujfat of Potafh and Lime. The pre-fence of iron in waters is equally well indicatedby thefe pruffiats, and if the prufliat of potafhis properly prepared, it will only be precipitatedby a metallic fait, fo that manganefe and copperwhen prefent will alfo be detedled, the formergiving a white, and the latter a red precipitate.

12. Lime Water. This is the common tellfor carbonic acid, as it produces a cloudinefsand precipitate with water that contains any ofdiis acid in whatever Hate of combination. Itis however ambiguous, as it decompofes all themagnefian falts, and the ma'gnefla which is thusfeparated being abfolutely infoluble in waterfalls down as a white precipitate. The alumi-nous falts are decompofed in the fame manner.Lime-water alfo produces a cloudinefs withmoll of the fulphats, owing to the formation offelenite.

13. Ammonia. This alkali, when perfectlycaullic, ferves as a diftin£tion between thefalts of lime and thofe of magnefia, as it preci-pitates the earth from the latter clafis but notfrom the former. There are however twofources of error in the ufe of this alkali for thispurpofe, one is where carbonic acid is containedin the water, either free or united with mag-nelia, in which cafe the ammonia becomespartially carbonated, and then alfo decompofesthe folutions of lime. The other is where anyfait of aiumine is contained, as ammonia willdecompofe thefe as well as the magnefian falts.The former fource of error may be obviated byadding a few drops of nitric or muriatic acidto the waiter, and boiling it for a fhort time, bywhich the carbonic acid will be got rid of, andthe earths will remain in folution. Then todiftinguifh and feparate magnefia from aiumine,rediffolve both in muriatic acid, precipitate thefolution by carbonated alkali, and then tranl-fer the precipitate into cold acetous acid, bywhich the carbonated magnefia will be diredllydiflolved, and the aiumine left.

14. Carbonated Alkalies . Thefe are fo farufeful tells that they precipitate all the earths

from their folutions. This is much haftened byboiling for a few minutes. Where carbonat ofpotafli is ufed particular care fhould be takenof its purity as it generally contains filex.

15. Muriated Aiumine. This tell is propofedby Mr. Kirwan as indicative of carbonatedmagnefia in waters, and which cannot, likecarbonated lime, be totally feparated byebullition, but remains till the whole liquid isevaporated. By adding muriated aiumine tothe boiled water a precipitate of carbonateda'umine is found, if carbonated magnefia isprefent, but in no other cafe, unlefs there bean excefs of alkali, which may ealily be neu-tralized.

16. Barytic Salts. The nitrat, muriat, andacetite of barytes are all equally good tells offulnhuric acid in any combination. The powerof this precipitant is greater than that of anyother, except perhaps the falts of filver for mu-riatic acid. In applying the barytic falts theonly care required is to neutralize any excefsof alkali that there may be, with any acid butthe fulphuric; and if the fulphureous acid befufpected, which is very rare, to free the waterfrom it. The nitrat or acetite of barytes arefometimes preferable to the muriat, inafmuchas they introduce into the water to be examinedno acid of a kind fimilar to any already con-tained. If any excefs of alkali has caufed amixture of carbonat with fulphat of barytes,they may be readily feparated by digeitionwith moderately dilute nitric or muriatic acid,which will difiolve the carbonat and leave thefulphat.

17. Salts of Silver. The falts of filver arethe mod delicate tells for muriatic acid in anycombination, producing the precipitated muriatof filver or luna cornea, the compofition ofwhich is conftant, and has been mentionedunder filver. Any excefs of alkali in the waterfhould be previoully faturated by pure nitricacid. The nitrat of filver is the fait commonlyufed as a tell, but this as well as the acetitewill alfo decompofe the alkaline and earthyfoluble falts with fulphuric acid, and a fulphatof filver will be formed, which it is not eafy todiftinguifh by the eye from the muriat. Thismay be' prevented cither by previoully gettingrid of all fulphuric acid in the water by meansof nitrst or acetite of barytes, after which all theprecipitate of filver will be luna cornea ; or elfeby employing a folution of iulphat of filver,which will then only a£l on the muriats. Itfhouhl be obferved however 'hat nitrat of filver*s a much more powerful precipitant of the