SUL

SUL

( 569 )

fluffed "with ffraw (called carboys ) and is thenbrought into the market, under the name ofOil of Vitriol .

d he fulphuric acid obtained from the diftil-lation of green vitriol exifts ready formed inthe fait, its extrication is a perfedlly fimpleprocefs, and the only impurities that it can pof-fibly contain are fulphurous acid, and a veryminute portion of oxyd of iron, and of theearth of the retort. When loaded with ful-phurous acid it has a fuffbeating odour, andwhen expofed to .the air gives out a white va-pour like ftrong muriatic acid; it ufed formerlyto be fold in this Hate by the name of fuming oilof •vitriol , and was further diftinguiftied by itsproperty of congealing into a foft ice, at a very.moderate degree of cold. By dilution with alittle water, and fubl'equent boiling for a fewminutes in a glafs vefiel, the fulphurous acid isdriven off, and the refidual fluid is commonfulphuric acid in a ftate of very confiderablepurity.

It might be imagined a priori, that fulphurwould be convertible by fimple combultion intofulphuric acid, this however is by no meansthe cafe. In the firft rude attempts to obtainfulphuric acid by this procefs, the method em-ployed was the following*, a large (hallow ba-ton was half-filled with hot water, and anearthen crucible, or other convenient vefielfilled with melted and ignited fulphur, wasfixed by means of a (land in the middle of thebafon, and juft above the furface of the water;a large bell glafs was then whelmed over thepot of fulphur, and brought nearly though notquite in contadl with the water; in this fitua-tion the vapour arifing from the combuftion ofthe fulphur, rofe into the bell glafs where itmixed with the (team of the hot water, andcondenfing trickled in drops down the fides ofthe glafs into the bafon. But though by thisprocefs a certain quantity of fulphuric acid wasobtained, yet fo large a portion of the fulphurefcaped in incondenfible fuftbeating fulphur-ous acid gas as to render it both a very offen-five and uneconomical mode of proceeding.Nor does the want of fuccefs in thefe experi-ments appear to have arifen from any imperfec-tion of the apparatus or want of care in themanipulation, for they have fince been repeated• ^ ar '° us manufacturers on a great fcale, butwith the fame refult as at firft. Chaptal ap-pears to have bellowed particular care on thisfubjett, we (hall therefore (late the refults ofhis experiments. 11 The apparatus employed by

this able chemift was a leaden chamber with a(love conftruCted on the outfide, and communi-cating by means of a flue with the chamber.In this (love the fulphur was melted, and ablaft of air being diredled on its furface, com-buftion took place, and the products of thiscombination pafl'ed into the leaden chamber,and were thus brought in contact with thewater which it contained. When the currentof air palled very rapidly over the fulphur, onlya very fmall quantity of this latter fulleredcombuftion, the ’greater part being Amply in-volved in the air in a minutely divided ftate,

. and depofited within the chamber in the formof flowers of fulphur. By moderating the ra-pidity of the current of air, the combination of" the fulphur with oxygen is more complete, alarge quantity of fulphurous acid is produced,and part of the fulphur is found covering thefurface of the water in form of a thin elaftic(kin. If the current of air is rendered (tillflower, fo as but juft to keep up the combul-tion, the whole of the fulphur is acidified, butfo large a portion of it is in the ftate of incon-denfible gas, that the product of true fulphuricacid is altogether infignificant. In one of M.Chaptal’s experiments he burnt in the courieof (even days 1135 lbs. of fulphur, at the endof which time fo prodigious a quantity of fut-focating gas poured out from the chamber asto render it neceffary to (top the procefs; inthree or four days after, the door of the cham-ber was opened, and after the gas had efcaped,it was found that the water on the floor of thechamber was covered with a flexible skin offulphur, and was fcarcely at all acidulous tothe tafte.

In a fecond experiment the combuftion wasmuch flower, 2900 lbs. being burnt in thefpace of thirty-three days; during .the procefsmuch fulphurous acid gas efcaped, and on thechamber being opened there was no appearanceof fublimed fulphur or of film upon the water,fo that the whole of the fulphur had undergonecombuftion, but the product of condenfibleacid was fo fmall that the water was only(lightly acidulous, and fcarcely effervefeed withcarbonated alkali. Hence it appears, thatthough atmofpheric air will effefi the combul-tion of fulphur, yet the product is little elfethan incondenfible fulphurous acid.

Several other methods have been tried tofupercede the necelfity of employing nitre, butwith little or no fuccefs. Water contains alarge proportion of oxygen in its compofition

* An. ale.Chim. ii. p. 36.

3 a

VOL* IT.