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and is readily decompofeable at a moderate heatby a variety of fubftances, attempts have beenaccordingly made to employ it for the oxygena-tion of fulphur. If to fome of this latter whenmelted and ignited, there be added water dropby drop, at fhort intervals, the flame of thefulphur will be enlarged, its colour will becomeof a yellowifh tinge, and a denfe white vapour•will arife from it, but this latter when condenfedappears to be only very {lightly acidulated waterhighly charged with minutely divided fulphur. cA more likely method of producing fulphuricacid was by mixing with the fulphur a portionof black oxyd of manganefe, capable of furnifh-ing a quantity of oXygen equal to that containedin the proportion of nitre ufually employed,but though this mixture has been treated invarious ways, it does not appear capable offurnifhing a greater quantity of fulphuric acidthan when fulphur is Amply burnt in atmof-pheric air. Even oxygen gas itfelf when diftri-buted by means of a pipe over the furface ofheated fulphur is by no means comparable inin efficacy to nitre; the rapidity of the com-buflion is indeed very rapidly increafed, butthe predudd is almofd entirely fulphurous acidgas.

When the method of producing fulphuricacid by the combuftion of fulphur and nitrewas firfd difcovered, the apparatus employedwas a feries of very large glafs balloons, at thebottom of each of which was a little water tocondenfe the vapour; only a fmall quantityof the mixture could be burnt at once, and con-ftant fuperintendence was neceflary to fupplythe balloons with frefh charges of the materials.In order to fave much of this manual labourand the heavy lofs arifing from the frequentfracture of the veflels, leaden chambers weremade ufe of, which befides requiring lefs atten-dance, and being upon the whole cheaper,rendered it eafler for the manufacturer to ex-tend his eftabliihrnent to any required magni-tude. Thefe chambers are of various con-ftruddion ; the mofk Ample and in moll generalufe, are furnifhed only with two apertures,namely, a fmall door, by which the water andthe fulphur and. nitre are introduced, and aleaden pipe with a ltop-cock, by which thewater wiien acidulated is drawn oft; otherchambers have befides a few fmall aperturesfor the introduction of atmofpheric air duringthe combuftion, and a fleam pipe conneddedwith a boiler, it being found that if the wateris introduced in the fdate of fleam, a much

more rapid condenfation of the acid enfues thanin the ufual way of proceeding. In fome ofthe belt contrived chambers the combuftion ofthe nitre and fulphur is effected in a feparateftove, and the acid vapour thus produced ispoured by means of a pipe into the condenfingchamber.

There is a good deal of difference among themanufacturers as to-the proportion of nitre em-ployed, by fome it is made equal to of thefulphur, while by others it is not allowed toexceed X V- This however appears to be fatis-faCtorily eftablifhed, that within the above limitsthe greater' the proportion is of nitre, the moreeafily condenfible will the acid vapour be, andthe lefs fulphur will be loft in the form offulphurous acid gas. If the nitre exceeds -§- ofthe fulphur, the combuftion will be fo rapid asto drive into the chamber a conftderable pro-portion of fulphur unaltered. The acid vapouris of a denfe opake white colqur, and accordingto Chaptal is conftderably luminous: when asmuch of it is condenfed as is capable of beingfo in the ufual procefs, the reftdue becomesquite tranfparent, and is for the moft part amixture of fulphurous acid gas and nitrousgas; it has a peculiar and very pungent fufFo-cating odour, and upon opening the door ofthe chamber, it prefently acquires a faint orangered colour, by combining with the oxygen ofthe air, and thus forming nitrous acid vapour ;this as foon as formed re-adds on the leadenlining of the chamber, corroding it deeply, andis the principal caufe of the fulphat of lead,which common fulphuric acid always contains,and often in conftderable abundance. It wouldconduce much to the purity of fulphuric acid,and might probably be found even to be aneconomical plan, to line the chamber with glafsinftead of fheet lead; the general appearanceof the chamber would then refemble a green—houfe, and all the wood work fhould be facedinternally with glafs; a compofttion of wax,maflich, and fine fand, would form a ftrongcement for the glafs, and little liable to be addedon by acid vapours, more efpecially if the in-terfdices filled up with it were dufted withpowdered glafs or very fine land, while thecement was yet warm and adhefive. Such achamber would have the additional advantage-of allowing the operator to fee what was pallingwithin, without the neceflity of opening thedoor.

With regard to the ftrength of the acid whenwithdrawn from the condenfing chamber, we

« Chaptal, Application de Chimie aux Arts, &c. Vol. II.

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