SUL

SUL

( 366 )

hydro-fulphureous talle which foon goes off,leaving nothing in the mouth but folid fulphur,flicking to the teeth.

When a folution of potafii is added to fuper--fulphuretted hydrogen, a frrftll portion of ful-phuretted hydrogen exhales, and the remainderunites with the potafh forming a folutionwhich refembles in every refpeft the commonliquid lulphuret of potalh.

As the foregoing fubjecl is fomewhat intri-cate, it may be ul'efui to recapitulate fhortly,the various combinations of fulphur, hydrogen,and an alkaline or earthy baits, with their dif-tinguifhing characters.

I. Sulphuretted Hydrogen, a gas fomewhatheavier than common air, compofed of hydro-gen holding fulphur in folution; has a peculiarfetid fmell, is inflammable, is abforbed by water,does not render lime-water immediately turbid,when in liquid folution is readily decompofedby expofure to air, or by the acids which eafilypart with their oxygen, fuch as the nitrous andox ymuriatic, during which its hydrogen is firfhengaged and quits the fulphur, which thereforeis precipitated in its natural form. Sulphuret-ted hydrogen reddens litmus, unites largelywith alkaline and earthy bafes, forming withrnoft of them cryftallizable falts in which thebale is nearly if not entirely neutralized, fepa-rates fulphur from its combination with alkalies,and in all thefe reipects performs the function ofan acid. It is however detached from its com-binations by every acid, and then re-aflumes itsgaffeous form, and pafles off by effervefcence.It blackens the folutions of many metals, andprecipitates mod of them, but not the falts ofiron and manganefe.

8 »2. Hydro-fulphurets are the faline combina-tions of iulphuretted hydrogen, with the feveralalkaline or earthy bafes. They are, when re-cently made, perfectly clear and colourlefs, andor, the affufion of a Itrong acid they effervefee,.and give out abundance of fulphuretted hydro-gen, but no fulphur is precipitated, the hydro-gen being fnfficient to carry off the whole of it.The fulphur therefore is iolely that which be-longs to the conftitution of fulphuretted hydro-gen. The hydro-fulphurets by expofure to air,abforb its oxygen, and in fo doing lofe a propor-tionate quantity of their hydrogen, wherebythey turn yellow and cloudy, and on the affu-iion of an acid they then both effervefee, anddepotit fulphur, fo that in this ftate the iulplvuris in excels relatively to the quantity of fulphu-retted hydrogen.

3. Sulphuretted Hydro-fulphurets are hydro-fulphurets holding an excefs of fulphur in folu-tion, and are made either by digefting the purehydro-fulphurets with fulphur, or by expofingthem to the atmofphere for a fhort time, tillthey turn yellow, and till a portion of the hy-drogen is deftroyed. The former method how-ever gives the moll concentrated folution.Thefe compounds on the affufion of muriaticacid both effervefee and depofit fulphur, buton palling a fveih portion of fulphuretted hy-drogen through them, no fulphur is feparated,and in this lad circumllance they differ fromthe common liquid fuiphurets.

4. Super fulphuretted Hydrogen is that lingularliquid produced by decompofing a liquid ful-phuret by a large quantity of acid, and confillsof fulphuretted hydrogen exceffively loadedwith fulphur, and adhering to it fo loofely astotally to quit it on applying a gentle heat, orexpofure to air. An alkaline bafe therefore isa neceffary intermede to effeft a permanentunion between fulphur and fulphuretted hydro-gen, and hence the addition of an alkali to thisfuper-fulphuretted hydrogen, brings it to theftate of fulphuretted hydro-fulphuret.

5. Dry Sulphurets or Hcpars. Thefe areAmple combinations of fulphur and alkali ef-fected by fufion at a low red heat. When thealkali is carbonated a part of the carbonic acidremains in union, and is expelled by an acid.The dry fuiphurets of the alkaline earths canonly be made by decompofing their fulphats byfufion with charcoal, and then are impure.

6 . Liquid Sulphurets. The folution of anydry fulphuret in a watery liquid, or of fulphurin a liquid alkali or alkaline earth, generates aquantity of fulphuretted hydrogen (though inno degree proportionate to the fulphur dif-folved) which mixes with the other conftituentsand the whole forms a cauflic yellow liquidwith ftrong alkaline properties. It is compofedtherefore of the fame materials as the fulphu-retted hydro-fulphurets, that is to fay, of ful-phuretted hydrogen, fulphur, and an alkalinebafe, but differs from thefe falts in containing amuch larger excefs of fulphur, and a muchfmaller quantity of fulphuretted hydrogen, andhence the affufion of an acid caules in generalonly a fmall effervefcence (lometimes hardlyperceptible) but a copious reparation of ful-phur; and befides (which is a diftinguifhingmark) much fulphur is precipitated by pallingthrough it a current of fulphuretted hydrogen.

In the liquid fuiphurets therefore the fulphurfeems to be held in folution by the alkali alone,