WAT

WAT

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tie In water) and not from the lime. . In eithercafe however the prefence of iron would proveembarraffing, and in theTatter much of it wouldbe volatilized with the muriatic acid, and there-fore we Ihould advife, firft to feparate it fromthe muriatic folution by pruffic acid or fuccinatof ammonia, then to throw down the earths bycarbonat of foda, to edulcorate, and rediffolvethem either in fulphuric or muriatic acid, ac-cording to the method of reparation adopted.On the whole we fhould prefer the fulphuricacid.

EJUmation of the remaining Subjlanccs.

We have now feparated from the water, andeftimated all the gaffes and all the earths andoxyd of iron held in folution by carbonic acid.The water therefore now can only contain fixedfalts, with alkaline, earthy, or metallic bafes,filex, and extractive or carbonaceous matter.If the prefence of carbonat of magnefia hasmade it neceflary to evaporate nearly to drynefs,and if any fulphat of lime has precipitated, itfhould be added to the remaining water afterthe magnefian carbonat has been abftracted.

It Ihould be premifed that if the tells indi-cated any ammonia in the water, it Ihould firftbe feparated by diftillation in the way alreadymentioned.

The further operations to be performed uponthe water mult be regulated in a good meafureby the contents pointed out by the different re-agents. If, for example, no earthy fait nowremains, but both fulphuric and muriatic acidare indicated, and at the fame time no excefsof acid or alkali exifts, we may conclude thatall the remaining faline ingredients are fulphatand muriat of foda (potafh being extremely rare)and it then becomes a queftion which is the beltmode of eftimating their refpefiive quantities.If at the fame time an excefs of alkali exifts,we may conclude that together with thefe faltscarbonat of foda is contained.

The way of afeertaining the fixed falts of anymineral water, which till lately has been themoft frequent, is that recommended by Berg-man, and which indeed would firft fuggeftitfelf, namely, to evaporate the liquor till theleaft foluble fait began to cryftallize, and thenby a judicious alternation of gradual warmth,and of cooling, to endeavour to obtain the dif-tin£t cryftals of each fait to the laft drop of thefolution.

But though evaporation and cryftallization areextremely ufeful and indeed almoft indifpenfibleto fatisfy the chemift as to the real nature of

the faline and other contents, it has long beenfound impracticable even by the moft Ikilfuloperators, perfectly to feparate any two falts inthis manner. This is caufed partly by the in-creafed folubility which two falts give to eachother when held in folution in the fame liquid ;partly by the change in the natural form ofcryftals which is fometimes produced; andpartly by the extreme difficulty of picking outcryftals which grow more and more minute inproportion as the bulk of the folution is leflenedby the repeated abftraftion of its contents.The great difficulty too in retaining exactly thefame proportion of water of cryftallization isanother objection to this mode, though thismight be remedied by expofing the fait, whenobtained, to fuch a degree of heat as will pro-duce an uniform deficcation. The belt analyftstherefore have nearly abandoned the attempt ateftimating acftua! quantities of faline ingredi-ents (where accuracy is required) by cryftal-lization, except where no other mode can wellbe adopted, as is the cafe with the nitrous falts.The method commonly preferred is to decom-pofe thefe falts in fuch a manner as to producean infoluble precipitate with one or other oftheir ingredients, and from the weight of thisto eftimate (from previoufly known data) thequantity of the decompofed lalt. The faltswith alkaline bafes are eftimated by the preci-pitate which their acids form with earthy ormetallic bafes; the fulphats, for example, areanalyfed by falts cf barytes or lead ; the muriats,by falts of filver; the borats, by lead, &c. Thefalts with earthy bafes are eftimated by fepa-rating either their earth (generally by a car-bonated alkali) or their acid, and where itcan be done it is more fatisfadtory to employboth.

Another procefs is ufed to afeertain quantitiesof unneutralized acid or alkali exifting in anywater, as of foda for example, or rather itscarbonat, which is a frequent ingredient inmany hot mineral waters. This was firft ufedwe believe, by Dr. Black, in his analyfis of theIceland hot waters, c and it confifts in exadtlyfaturating the alkali with a portion of any acid(or vice verfa , the acid with an alkali) whofeftrength has previoufly been determined bytrials upon known quantities of the fame acidor alkali. Thus in the above example a verydilute vitriolic acid was ufed, whofe power offaturating foda had been previoufly tried, andthe delicate teftj of litmus and violet were em-.ployed to hit the precife point of faturation,hi.

€ Edii?b. Traufudl. V«I.