WAT

WAT

( 4S3 )

turn up the mouth of the bottle and blow outthe refiduary air. If the hepatic fmell continuesin the water, repeat the addition of nitrous airas above till the fmell is deftroyed. Then adda few drops of nitrous acid to prevent the pre-cipitation of the earths, heat the water to 150°for an hour and filter it. The excefs of weightwhich the dried filter will gain over its originalweight will indicate the weight of fulphur fetfree by this procefs, from which the quantityof fulphuretted hydrogen may be eftimated,allowing 3.33 cubic inches of the gas for everygrain of fulphur.

But under the article fulphuretted hydrogenwe have {hewn the great diverfity in the efti-mation of its compofition by two very ablechemifts; a diverfity which perhaps may arifefrom fome error in the mode of computation,or with equal probability may depend on a realvariation in the proportion of the conftituentsof this gas according to the mode in which it isprocured or other circumltances. Hence wecan have but little reafon to trull implicitly inthe mode of eftimating quantities of fulphurettedhydrogen by the a£tual weight of fulphur pro-duced, efpecially in fuch dilute folutions of thisgas as the native fulphureous waters are, ofwhich fome of the flrongeft, fuch as that ofHarro. ate, contain no more than about T V °ftheir bulk.

Eflimation of t he Earthy and Metallic Carbonate.

Thefe when they occur fhould next be ex-amined. They are, carbonat of magnefia, oflime, of iron, and fometimes of alumine. Ofthefe the three latter are totally precipitable byebullition for a quarter of an hour, but the for-mer only' partially, and is not totally feparatedtill the water is evaporated to a very fmall bulk.A given quantity therefore of the water (whichmay be the portion from which the gafl'es havebeen feparated by ebullition) fhould firft beboiled for a quarter of an hour, and after {landingfor a time the earthy fediment may be collected,edulcorated and dried. Then add dilute coldmuriatic acid, which can rediflolve only lime,magnefia, and oxyd of iron, and leave the alu-mine. Add cauftic ammonia by drops to thefolution, which will feparate firft the oxyd ofiron coloured, and then the magnefia nearlywhite, whilft the lime will remain. If no mag-nefia is detected, nothing further is necefllryihan to afeertain the atlual quantities of thecarbonats of lime, iron and alumine, the latterbeing left undiffolved by the muriatic acid,and, of the two former, the iron alone beingprecipitated by ammonia ; and thus each

fubftance is obtained feparate, and may bebrought'to their original Hate of carbonat byfublequent proceffes which will eafiiy fugged:themfelves. But if the fediment depofited byboiling the water contains any carbonat of mag-nefia, it is a proof that fome of the fame earthyfait remains in folution, which may alfo befurther confirmed by the boiled water giving aprecipitate with muriated alumine. In this cafea confiderable quantity of the water fhould beboiled down uninterruptedly to the bulk of afew ounces and allowed to cool. Then colledlthe entire fediment, edulcorate it and dry it. Itnow contains all the earthy and metallic car-bonats, but is perhaps mixed with fome felenite,which is depofited towards the end of the eva-poration. Cold dilute muriatic acid .will thenrediflolve the carbonats of lime, magnefia, andiron, and leave the felenite as well as the alu-mine. The muriatic folution then contains alland only the lime, magnefia, and oxyd of ironwhich exilted in the water in the {late of car-bonat, thefe Mr. Kirwan propofes to feparatein the following way. Add ammonia to thefolution to. feparate the magnefia and iron andleave the lime. Rediflolve the magnefia andiron in muriatic acid, and precipitate both bycarbonat of foda, and expofe the precipitatewhile moift to the air for a few days. Diftilledvinegar applied without heat will then rediflolveonly the carbonat of magnefia and leave theiron. The reafon of this fecond folution of themagnefia and iron is in -‘order to carbonate themagnefia by precipitation with a carbonatedalkali, for when this earth is pure it is not eafiiyfoluble in acids, and it is by the eafy folubilityof its carbonat that it is to be feparated fromthe oxyd of iron in this inftance.

The above method of feparating the earthsand iron is inaccurate, inafmuch as it is fullyafeertained that ammonia will never feparatethe whole of the magnefia from its acid folu-tions, and therefore though it is extremely ufe-ful as a tell to aflay any liquor for magnefia, itcannot be depended on to give the adlual quan-tity of this earih. The difficulties and the beltmethods at prefent known of feparating limeand magnefia, are mentioned under the articlesSulphat (p. 380), Mur at (p. 133), and Lime ,(p. 41). They are, either by convening bothinto fulphats and calcining the mixture, whichwill render thefulphat of magnefia alone folublein cold water or by convening them into mu-riats and beating them nearly to rednefs, bywhich the muriatic acid is driven off from themagnefia alone (whereby it is rendered infolu-3 r *