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( 301 )

and filver but alfo fulphuric acid. Now asmuriatic acid is incapable of acidifying fulphurit follows that the above mentioned acid mullhave pre-exifted in the ore. This is furtherconfirmed by an obfervation of Henkel’s thatthe filver may be extracted from the'red oremerely by fucceffive digellions in muriatic acid,which could not have happened without theprefence of fulphuric acid likewife. We fhallreturn to the confideration of this queftionprefently.

The analyfis of this ore by Vauquelin' wasthus conducted.

a. ioo parts of the ore finely pulverizedwere treated with 400 parts of nitric acid, and200 of water: the colour of the mineral becameby degrees grey and then palled into white.During the whole of this change there wasno perceptible difengagement of nitrous gas,whence it may be concluded, fays the author,that the ingredients of the ore were alreadyfufficiently oxygenated to difiolve in nitric acid.After a gentle ebullition, the whole wasthrown on the filter, and the infoluble portionafter edulcoration weighed 42.06

b. The infoluble portion was digefted inftrong muriatic acid, by which its colour becameyellow, and its amount was reduced to 14.66.Being then laid on a hot coal it burnt entirelywith a blue flame and all the other charactersof fulphur. The fulphur of the ore thereforemay be reckoned at 14.66

c. The muriatic folution being poured intoa large quantity of water, depofited a whiteflocculent precipitate of oxyd of antimony,weighing 21.25 an d compofed, according toVauquelin, of 16.13 antimony, and 12.12oxygen.

d. The nitrous folution (a) was mixed withmuriatic acid, and furnilhed 72.66 of muriatedfilver, equivalent, according to Bergman, to56.67 of metal.

In this analyfis by Vauquelin there is nomention made of fulphuric acid which wasfound fo abundantly by Klaproth : and in orderto bring this matter more compleatly to an iflue,100 parts of the ore were digefted with afolution of cauftic potafti. As foon as the twofubftances came into contact, the colour of theore changed firft to grey, and prefently to ablack; 66. parts remaining undiflolved.ihefe were then treated with dilute nitric acidat a gentle heat, upon which a difengagementof nitrous gas took place, and the undiflolvedmatter amounted only to 8. parts, and was

fulphur. The nitric folution on the additionof muriatic acid afforded 70 of muriated filver.The alkaline folution, which was perfectlyclear and colourlefs, gave, when treated withmuriatic acid, 32. of antimonial kermes: afterthe feparation of this, the refidual liquor wasmixed with muriat of barytes without any pre-cipitate being formed: hence it contained nofulphuric acid. Indeed Klaproth himfelf at theconclufion of his diflertation on this fubjedl, isdifpofed to think that the fulphuric acid, asfuch, does not exift in the ore, but that thewhole of the fulphur is in the ftate of oxyd,and by the aftion of the menftrua employedin the decompofition of the ore, the whole ofthe oxygen unites with part of the fulphur,converting it into fulphuric acid, and leaving theremainder of the fulphur compleatly deoxyge-nated. But we do not fee how this can bethe cafe: befides it is obvious that the filver atleaf! mull be in the ftate of oxyd, fince itdiflolves in nitric acid without producing anynitrous gas. If it were not therefore for thecircumftance that the ore when treated withfimple muriatic acid gives out fulphuric acid,we fhould be difpofed to believe that the ore con-tains no fulphuric acid, and that the oxygen iscombined not with the fulphur but with the metal.

3. Sulphurated Silver.

The analyfis of this ore by Klaproth is veryfimple. After being cut into fhreds, it wasdigefted with 8 times its weight of nitric aciddiluted with half its bulk of water. When theaction of the acid had ceafed it was poured off",,and the infoluble refidue being dried andweighed, was burnt on a teft: the fulphurwas thus driven off 7 , and there remained behinda little fulphat of filver, which was then re-duced to the metallic ftate by fufion with carbo-nated foda. The nitrous folution, on theaddition of common fait, gave a precipitate ofmuriated filver, and nothing elfe remained inthe liquor except a minute portion of fulphuricacid formed no ooubt by the aftion of thenitric acid on the fulphur of the ore. Toconfirm this analyfis two- allays were made inthe dry way, and the quantity of filver thusobtained not only correfponded precifely in each,of them, but alfo with that procured in the,analyfis.

4. Brittle Sulphurated Silver.

a. 100 parts of this ore when levigated:were boiled in dilute nitric acid till the original:black colour of the ore had changed to a,greyifh yellow.

* Journ. des Mines, No. 17* p* **