ME R

MER

( 74 )

compartment by an iron grate, and communi-cating near its top with a let of aludels. Thecharging of the furnace commences by layingon the grate a ftratum of flat rough Hones, leav-ing intervals between each for the pafiage ofthe fire: upon this is laid a bed of ore of thefecond quality, then the ore of the firft quality,afterwards another bed of the fecond kind, andat the top of all a layer of the third kind madeup into bricks. A few faggots are now throwninto the lower cavity of the furnace and lighted,which, in proportion as they are confumed, arefucceeded by others, and thus , a gentle fire iskept up for 8 or 12 hours, according to the pre-vious drynefs of the ore. When the moiftureis got rid of, which is known by the cefiationof the vapour, the fire-place is again filled withfaggots, and, before thefe are confumed, themals of ore will be fufficiently heated to con-tinue the combuftion by means of the fulphurthat it contains without any additional fuel.During the next two days, as the fulphur flowlyburns away, the mercury, in the ftate of vapour,pafles into the aludels where it is condenfed;and at the end of this period, all the metalbeing extracted, the_ fcorire are taken out of thefurnace, and the aludels are emptied of theircontents. Befides the mercury, a confiderablequantity of a black matter like foot is found inthe aludels, which is readily feparated by fpread-ing the v/hole about on an inclined table: themercury runs to the lower end, where it is col-lected in a channel, while the impurities remainbehind.

The confumption of fuel and coft of appa-ratus is confiderably lefs than in the Germanmethod, but it is probable that a portion ofmercury ftill remains in the ore. A great lofsis alfo fuftained by throwing away the foot afterfeparating the running, mercury on the tables,for not only many globules of the metal mudefcape notice, but alfo the calomel, cinnabar,&c. which it contains, are entirely wafted.This foot, previous to the feparation of themercury, confifts, according to Prouft- b , ofMercury . . 66

Calomel . . 18

Cinnabar . . 1

Water & fulphureousacid 2.5Sulphat of ammonia 3.5

Lamp black . 5

Selenite . . 1

97 -°

3. Lofs

100.0

Hence the obvious way of turning it to moft

profit would be firft to difiolve out tbe fulphatof ammonia, which might be difpofed of togreat advantage to the fal-ammoniac makers,then to mix the reft with x 2 or 15 per cent, ofquicklime, and diftill it in an iron retort, bywhich procefs not only tbe'whole of the runningmercury would be driven over, but alfo thatarifing from the decompofition of the calomeland cinnabar.

On account of tbe fluidity of mercury it can-not be conveyed from place to place withoutextraordinary precautions. The method ofpacking it is as follows. A frelh found fheep-ikin with the hair taken off is laid over a woodenbowl, and from 50 lbs. to 75 lbs. of mercuryare poured into it; the ends of the Ikin arethen gathered up, and tied together with greatcare, thus forming a fort of bag in which themetal is iticlofed; this bag is inclofed in afecond fkin, and the fecond in a third: laftly,thefe bags are put into very tight barrels, ca-pable of holding from two to four of them, andin this ftate are brought into the market.

§. 3* Phyjtcal and Chemical properties.

Mercury is a metal always fluid at the tem-perature of our climates, of a white and per-fectly refplendent polifhed furface, fo as toreflect with extreme brilliance all objects, andis without fmell or tafte in the metallic ftate.Its fpecific gravity is 13.56. Its expansionby heat is on the whole very regular till aconfiderable diftance above the point of boil-ing water, and hence its ufe in the conftruc-tion of thermometers. When expofed to a coldof about —39 it folidifies, and when hard frozenit will bear gentle blows with a hammer, fuffi-cient to prove its malleability, though in fodoing, the friCtion foon heats it. enough to makeit reaffume the liquid ftate. Mercury boils atabout 66o°, and, if pure, totally evaporateswithout any refiduum: but the vapour fooncondenfes upon the adjacent bodies, coatingthem with a white dew, which is found bythe microfcope to confift of myriads of minuteglobules. When the galvanic fluid from apowerful apparatus is palled into mercury byimmerfing the conducting wire into this fluidthe mercury difperfes in beautiful, brilliant,'luminous ftars, which feems to fliew that this is.a combuftible metal.

Mercury is fcarcely if at all changed by mereexpofure to air for any length of time, but if itbe long agitated in any veflel it is flowly reducedto a black duft, foiling the_fingers, which, how-ever, on being heated, returns again to the ftateof running mercury, Boerhaave was the firft:

* An. <le Chim. iv. p. 216,