ME R
ME R
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turbid, acquires a metallic tafte, and with itthe power of deftroying infedts.
The falts produced by the union of mercurywith the different acids have been more exa-mined- than thofe of perhaps any other metal,and require to be defcribed fomewhat at large.The Sulphuric acid, has no adtion on mercury inthe cold, but when heated, folution immediatelybegins, attended with a copious produdtion offulphureous acid vapour, which vapour receivedin water produces the liquid fulphureous acidin great purity ^ which is often prepared in thisway. The mercury of courfe becomes oxyge-nated by the deoxygenation of the acid, and theoxyd diffolves in the remaining acid forming afulphat of mercury. There are however as hasbeen Ihewn by feveral chemifts, and particu-larly by the accurate experiments of Fourcroy,feveral diftindt falts and combinations of ful-phuric acid and oxyd of mercury producedeither by the proportions of the ingredients, orby the heat employed. Two parts of mercuryto three of ftrong fulphuric acid are the pro-portions generally ufed. If the dillillation ofthe acid from off the metal is flopped when themixture has become a white faline mafs, butbefore it is adtually dry, the fait is very acridand corrofive, with a ftrong excefs of acid, anddeliquefees if expofed to the air. In this ftateit is called by Fourcroy the Acid Sulphat ofMercury, or as we fhall here term it the fuper-fulphat of Mercury. This fait may contain avariable proportion of acid, and it is more fo-luble in water as the quantity of acid is greater.On the average it requires about 155 parts ofcold water and only 33 of boiling water, andgives an orange precipitate with the fixed alka-lies. If this fait be walhed with a much fmallerquantity of cold water than isneceffary to diffolveit, it lofes a part of the mercurial oxyd to-gether with the whole excefs of acid, and if thewafhing be continued with fmall dofes of watertill the liquor ceafes to turn blue vegetablecolours red, and to give any proof of acidity, thefait that is left is found to be much changed inits nature. It' is now white and not very acrid,requires for folution as much as <500 parts ofcold, and about 230 of boiling water, and whencryftallized from the hot faturated folution itappears in line acicular prifms, which whendry, contain according to Fourcroy (the difco-verer of this ialt) 75 parts of mercury, 8 ofoxygen, 12 ol fulphuric acid, and 3 of water.The pure, alkalies and lime-water alfo precipi-
tate the metallic oxyd of a grey colour. In thisfait the acid and metallic oxyd appear in a ftateof mutual faturation, and hence it fhould betermed fimply fulphat of mercury. As it differsfrom the fuper-fulphat merely by lofing theexcefs of acid, fo it may readily be reftored tothat ftate by adding acid, and then its folubilityin water proportionally increafes, and it givesan orange precipitate by alkalies.
There is ftill another fulphat to be noticed.If the 'white faline mixture of fulphuric acidand mercury, or the fuper-fulphat above de-fcribed, be urged ftill further in the fire in aheat confiderably above that of boiling water, itparts with a ftill greater portion of acid, andbecomes a dry hard grey mafs.
If this be taken from the fire and boilingwater poured on it, it immediately falls into alemon-yellow powder, which, when well edul-corated with cold water, forms a well-knownmercurial preparation, the Turbith mineral, or asFourcroy names it, the fulphat of mercury withexcefs of oxyd, or in other words, the fub-fulphatof mercury. In making this preparation it iseffential that all the excefs of acid Ihould bedriven off by heat before the boiling water isadded, otherwife the change of colour takesplace very llowly and partially, and the waterdiffolves the remainder.
Turbith mineral approaches very nearly tothe ftate of a Ample oxyd ; however it ftill re-tains a portion of acid, and hence, when heat-ed ftrongly without addition, it gives out waterand fulphureous acid gas,-after which comesover a confiderable quantity of oxygen gas, andlaftly the reduced mercury diftills over in itsmetallic form. Turbith alfo differs from boththe fuper fulphat and fimple fulphat of mercury,in being diffolved and decompofed by the nitricacid. U is likewife nearly iufoluble in water,though, according to Fourcroy, a folution iseffedted by 2000 parts of cold water. Whenrubbed with running mercury the globules ofthe latter difappear, and the whole is changedto a black oxyd. A hundred parts of turbithcontain 10 of fulphuric acid,* 1 76 of mercury,11 of oxygen, and 3 of water.
The action of ammonia upon the fulphats,and on mod of the other lalts of mercury, isinterefting and fomewhat complicated. The ex-periments of Fourcroy have affiited materiallyin explaining this fubjedt. When ammonia isadded to a neutral fait of mercury (the fulphatfor example) three feparate actions take place;