MANUFACTURES.
43?
“ r ocess
f es cribedV Dr.A-ikin.
Manufac-tures. Vitriol Works.
lU anu f a c_ (627.) Sulphuric arid or oil of vitriol .—Sulphurichire u f sul- ac 'd is largely employed in various branches of the Artsl’huricacid. an d Manufactures. It was formerly wholly obtainedby distillation from sulphate of iron, and this practiceis still followed in some parts of the Continent; but theprocess generally adopted in this Country is by the com-bustion of sulphur and nitre, and is described by Dr.Aikin to consist of, first, having a chamber constructedof framework and lined with strong sheet lead, the onlyopening being a small door, made to shut very close,the bottom of which is a little higher than the floorof the chamber. Water is poured into this chamber tillit rises to the height of an inch or two from the floor,and a stand is introduced, in which is placed an earthenpot, containing a few pounds of sulphur and of nitre,in the proportion of from eight to ten of the former toone of the latter; this mixture is set on fire by meansof red-hot iron, and the door immediately closed ; at theend of about six hours another charge of sulphur andnitre is introduced, which, after a similar interval, is re-placed by a third, and so on, without intermission, for afortnight or three weeks. At the end of this time, thewater in the chamber is sufficiently acidulated, and isthen transferred to a leaden boiler, where the greaterPart of the water is evaporated ; in proportion, however,as the acid becomes more concentrated, it has the moretendency to corrode and dissolve the lead of the boiler;therefore, before it arrives at this state it is transferredinto large, green glass retorts, where a degree of heat isSu pplied sufficient to drive off - almost the whole of theWater. As the acid becomes stronger it also becomesclearer and less coloured, in consequence of a portion ofthe acid reacting upon the impurities with whic ) it istinged and thus destroying them.
When the acid is thus brought to the required densityand clearness, it is poured out ot the retorts into largeglobular, glass bottles, surrounded with wickerwork and. Hied with straw, called carboys. In this state it is
J f )r -Ur e . r( j"g'ht into the market.
. f^ r - Ure’s description differs a little Irom the above and18 somewhat more minute. The ordinary form of the sul-phuric and lead chamber he states to be a parallelopiped,aj °ut seventy :eet long, ten or twelve high, and fifteenJ ri .. e> At the middle height of one end, a small oven isor 7 ll P with a cast iron sole, having a large lead pipe, tenint We J Ve inches diameter, proceeding from its arched topph° • e . etl( i °f the lead chamber. On the soie the sul-sar UF '? Durnet l> the combustion being aided, when neces-Al^’ ' heat applied from a little furnace below it.j„ ,° V< T tlle flaming sulphur a cast iron basin is supportedof th ' r0 ? ^ rame > into which the nitre, equal toone-tenthcotnb . phur > is put, with a little sulphuric acid. Thein th USt , 10n °f the sulphur is regulated by a sliding doorcham^i°' en ' roof of the remote end of the large
atinos a Smal * orifice is left f° r the escape of theThis enca f azote and other incondensable gases,there^ pparat “ s is used for the continuous process. Butwhich '. another, or that of the intermitting combustion,the su]nh,'lT h 1 y °- f nolice - Long flat tra y s - containing'he chamh • mtre ’ are introdu ced into the interior ofmaterials ^wl ' nto ^ oven, and fire is applied to theber is rent t the sulphur is burned, and the cham-stream of "water T'u, su, P h urous and nitrous acids, aa smal! nine .., a , ro 'y" in * in determinate quantity, byvol. vn 416 su f e ‘ This causes a tumultuous
motion among the gases and the atmospheric oxygen,which favours the mutual reaction. As the steam con-denses, the sulphuric acid falls with it. Alter sometime, the chamber is aired by opening valves of commu-nication with the external atmosphere. The operationis then commenced anew.
Instead of using nitre, nitrous gas, disengaged fromnitric acid by sugar or saw-dust, is introduced into thechamber containing the fumes of burning sulphur,whereby the chemical reaction above described is pro-duced, and then steam is thrown in to complete theprocess and condense the sulphuric acid. The bottomof the lead chamber should never be covered with purewater, but even in the first operation with a dilute acid,introduced on purpose. When nitrous acid comes intocontact with water and an excess of atmospheric oxygen,it is converted into nitric acid and nitrous gas. Thisaeriform body gets more oxygen and changes to nitrousacid, and thereafter to nitric. Hence a chamber with itsbottom covered with water will, in some cases, fail inproducing any sulphuric acid at all. Water moderatelycharged with sulphuric and sulphurous acids preventsthe transition of nitrous into nitric acid, and allows the
Mechanical
Processes.
process of acidification of the sulphur to go on freely.
Ure’s Dictionary.
(628 ) Sulphate of zinc or white vitriol. —The im- Manufac-pure sulphate of zinc, called in commerce white vitriol, is tl *re ofof a bluish-white colour, with ochrey stains externally :it has a granular crystalline texture like loaf sugar,and is in irregular, lumps or masses. The English white vitriol is prepared for the most part by direct solu-tion of a metallic zinc in sulphuric acid, and is there-fore purer than the foreign, though it still contains aquantity of iron. Both kinds may be considerably,though not entirely, purified by solution in water, andthen abandoning the liquor to spontaneous evaporationin an open vessel containing some granulated zinc, thesulphate of lead will subside to the bottom, and otherforeign sulphates will be decomposed by the metalliczinc. The saline mass, when dry, is to be lix-iviatedwith cold water, and the clear filtered solution, afterdue evaporation, will afford regular crystals of sulphatedzinc.
(629.) Sulphate of copper or blue vitriol. —This is not Dhu>, vitriolmanufactured at large in sufficient quantity to give theprocess a place in this general list of what we have calledWorks, ifcopper filings or clippings of thin sheet cop-per be put into a glass vessel with about twice theirweight of sulphuric acid, and the mixture be heated, solu-tion will take place. When this begins, much sulphuricacid gas is given out, (and this is a very convenient way ofprocuring this gas,) and at last the whole is dissolvedinto a dark-coloured liquor, except a small quantity ofblack residue, which is the sulphuret contained more orless in all common copper, and by dilution in water theliquor becomes a fine blue. This solution, by due eva-poration and cooling, furnishes crystals also of the samecolour, and, when regular, which, however, they seldomare, they assume a rhomboidal shape, which is the blueor Roman vitriol of commerce.
(630.) Sulphate of iron or green vitriol.—'This salt Manufaois of extensive use in the Art ot dyeing and other pro- tllre of .cesses. It is not commonly formed by a direct combine- B leenvl,rl ° •tion of its natural ingredients, but is obtained from variouskinds of native sulphates of iron or pyrites.
The first English work of this kind was established atDeptford, where it is still carried on ; and several large3 L