SUL
SUL
( 384 )
by decompofing tlie carbonat, not by heat, butby an acid, and the lofs of about 22 per cent,.of carbonic acid by effervefcence was con-firmed in Klaproth ’s experiments by many un-exceptionable proceffes. If therefore, as wehave before mentioned, ioo parts of the purecarbonat lofe nearly 22 of carbonic acid by ef-fervefcence, and produce 117 of the fulphat(which is a Ample and apparently unexception-able experiment) the quantity of 76.5 per cent,of barytes in the fulphat mud be largely over-rated; for if too of the fulphat contain 76.5,117 will contain 89.5 of barytes, which is ob-vioufly incompatible with the other experi-ments, as the ioo parts of carbonat could notcontain more earth than 78 at the utmoft, whenit loft 22 by effervefcence.
Mr. Chenevix produced 694 of fulphat ofbarytes by acidifying 100 grs. of fulphur with.nitric acid, and precipitating all the liquors bynitrat of barytes; which is in the proportion of14.5 of fulphur in 100 of the fulphat. But ifioo of fulphat of barytes contain 66.6 of earthand 33.3 of acid, the compofition of fulphuricacid would be as 14.5 of fulphur to 18.8 ofoxygen, which is double the higheft eftimationof oxygen, and obvioufly impoffible. Can aquantity of nearly infoluble nitrat have mixedwith the fulphat and increafed its weight ?
In Mr. Chenevix’s next experiment the 43parts of fulphuric acid contained in 100 of ful-phat of lime, produced 183 of fulphat of bary-tes. According to Klaproth ’s analyfis of thislatter fulphat 43 parts of acidfhould only haveproduced three times as much fulphat of bary-tes, or 129 parts. The method employed byMr. C. was rendered complex by the introduc-tion of oxalic acid, yet it does not appear thatit would involve any material fource of error.But on the other hand, Klaproth m eftimatesthat 220 of fulphat of barytes are equivalent inacid to 160 of fulphat of lime, whence 100 ofthe latter would yield by decompofition 137 offulphat of barytes. Jt fliould all'o be obfervedthat Mr. Chenevix makes a much lower eftima-ation of the quantity of fulphuric acid in ful-phat of lime than Kirwan, Klaproth , and other-chemifts do; for by Mr. Chen,eyix, 57 of limeand 43 of acid conftitute 100 of the fulphat,but by the other eftimation xoo parts of per-fectly dry felenite, contain about 40 of limeand 60 of acid.
The difagreement of tbefe experiments per-formed by chemifts of acknowledged fkill andfidelity, might lead to the fuppofition of there
being more than one fpecies of artificial fulphatof barytes, with different proportions of acidand earth, but further experiments are requiredto determine this point.
A molt unexceptionable method of afeer-taining the quantity of barytes would be thefollowing: diffolve fome of the pureft tabularcryftals of muriated barytes in water, decom-pofe the folution by carbonated ammonia, walhthe precipitated carbonated barytes, and dry itfor half an hour in a low red heat. Take agiven quantity of this carbonat, faturate it withmuriatic acid, and note the lofs of carbonicacid, decompofe the folution by fulphat offoda, edulcorate the barytic fulphat, and dry itin a low red heat for half an hour, and weighit. Then take another equal or aliquot portionof the carbonat of barytes, diffolve it in thepureft nitric acid, evaporate the folution todrynefs, and gradually ignite the nitrat in aclean platina crucible till all the acid is decom-pofed and driven off, and the pure barytes aloneis left.
The refults of thefe experiments comparedtogether, would give as accurately as can well bedone, the quantity of carbonic acid, and ofbarytes in the carbonat, and of barytes in thefulphat.
Sulphat of Lime. Selenite. Gypfum.
Under the article Gypfum the different fpe-cies of the native fulphat of lime are deferibed.To this it may be added that this fait is mollextenfively diffufed over the earth, being foundin fmall quantity in almoft every commonfpring water to which it gives (in commonwith other earthy falts) the properties of hard-nefs or harfhnefs to the feel, and of curdlingfoap.
Sulphat of lime when taken into the mouthin fubftance is almoft entirely deftitute of tafte,owing to its very difficult folubility. It requiresfor folution about 500 parts of cold water, andfomewhat lefs of boiling water, fo that it igpartly depofited from the bot faturated folutionon {landing for fome hours. Though the quan-tity of fulphat of lime in folution in purewater is fo fmall, each of its ingredients maybe formed into {till lefs foluble falts, and a pre-cipitate will appear on the addition either ofoxalic acid which abftrafls the lime, or of abarytic fait which unites with the acid.
Sulphat of lime is rendered much more folu-ble in water by the addition of any acid, all ofwhich (the oxalic excepted) fimply diffolve
* Kirwan’s Addit. Obs.