SUL

S U L

( Sal )

pittt’nn takes place, either becaufe no decom-pofition occurs, or becaufe the new compoundsare equally foluble with the former. The fo-lutions of alumine and zircon, however, areprecipitated by the alkaline hydro-fulphurets,as well as all the metallic halts.

The action of the alkaline hydro-fulphurets■on metallic falts will be afterwards mentioned.

Sulphurets or Hepars, Liver of Sulphur.Sulfure of Berthollet, and other French che-miits.

When fulphur is melted with an alkali abrown uniform mafs is produced, which as longas it continues dry is a Ample combination offulphur and alkali. But while dilfolving in watera certain quantity of fulphuretted hydrogen is-immediately generated, which remains in thefolution and unites with the fulphur and alkali,but may be expelled by the addition of an acid,which at the fame time precipitates the greaterpart of the fulphur in a ft ate of purity. Theliquid fulphurets therefore contain fulphur, al-kali or alkaline earth, and fulphuretted hydro-gen, fo that they differ from the hydro-fulphu-rets of the fame bafes in containing a largeexcefs of fulphur, and therefore give with acidsa copious precipitate of fulphur, which theAmple hydro-fulphurets do not.

Berthollet confiders the fulphuretted hydro-gen in the liquid alkaline fulphurets as the in-termede by which the fulphur is dilTolved inthe alkali, and therefore as an elfential part ofthe compound, and he denies the poffibility ofa liquid fulphuret exifting without containingfulphuretted hydrogen in its compolition.Hence he terms thefe compounds Su fares Hy-drogenes , which Mr. Chenevix calls Hydroguret -ted Sulphurets , and which may with equal pro-priety be termed Sulphuretted Hydro-fulphurets.

But it is not every combination of fulphur,fulphuretted hydrogen, and a bafe, to whichthis term can, as we apprehend, be juftlygiven, but only to that compound in which thewhole of the fulphur may be fuppofed to beunited entirely with the fulphuretted hydrogen,and through its intervention, to the bafe-, or inother words, to a compound in which no fur-ther addition of fulphuretted hydrogen willcaufe a precipitation of fulphur. For the com-mon liquid fulphurets (made either by unitingfulphur to an alkali by fufion, and diflolving themelted mafs, or by boiling the alkaline folutionwith fulphur) contain a very large excefs offu’pbur, mod of which is feparated by everyac id, and alfo a great part of it by fulphuretted

VQfc. II.

hydrogen, which here as in many other in-ftances performs the part of an acid, and unit-ing to the alkali with a ftronger affinity thanfulphur does, expells part of it, but alfo .dif-folves another portion, and carries this latteralong with it into the compound which itthen forms. The proper fulphuretted hydro-fulphurets therefore are thofe which are madeby digefting a hydro-fulphuret with fulphur,which, as Berthollet has fhewn, takes up a por-tion of it, and again depofits it on the additionof a ftronger acid. Perhaps too the hydro-ful-phurets when they have been fo long expofedto the air as to turn yellow and depofit fulphurby the addition of an acid, may be, confideredas fulphuretted hydro-fulphurets, though in amuch lefs concentrated ftate than the former.

With regard to the common liquid fulphu-rets, Prouft has alfo fhewn that the proportionof fulphuretted hydrogen which they contain,varies fo much, and is fo little proportioned tothe quantity of fulphur actually prefent in thefolution, as to render it extremely improbablethat the whole, or even the greater part of thefulphur is united to the alkali in folution by theintervention of the fulphuretted hydrogenwhich they all confeffedly contain.

The fame excellent chemift has alfo given amethod (which we fhall prefen(ly mention) bywhich every fenfible portion of fulphurettedhydrogen may be extracted from the folution;whilft the alkaline bafe and the greater part ofthe fulphur remain untouched,—another pre-emptive proof that fulphuretted hydrogen isnot effential to the liquid folution^of fulphur inalkali.

We fhall therefore retain the terms dry andliquid fulphuret , to fignify the common folid andfluid combinations of fulphur with a bafe, andproceed to defcribe the individual fulphurets.

Sulphuret of Potajh. Common Liver of Sulphur.The combination of fulphur and potafh is thatwhich has been the longeft known to chemifts,and may be prepared in feveral ways. Theantient method is the following: mix two partsof dry carbonat of potafh with one of fulphurand melt the mixture in a crucible with a heatgradually raifed to rednefs, till the whole flowsinto an uniform mafs. As the potafh is car-bonated, a confiderable effervefcence arifes whenthe materials begin to melt; fo that the cruciblefhould be large and the heat gradual. Whenthe fwelling of the mafs has fubfided and thewhole remains in quiet fufion, pour it out on afinooth greafed ftone, and as foon as it is coolenepgh to be handled, break it and put the. . 2 Z