S I L

S 1 L

( 303 )

water afforded 97.25 grs. of antlmonial oxyd,equivalent to 75 grs. of metal.

h. The refidue {f) inl'oluble in muriaticacid, weighing 105.5 g TS> was ignited, and 25.25grs. of fulphur were thus burnt off. The re-maining filex was then fufed with four timesits weight of black flux, and afterwards diffolvedin water, leaving behind it 0.75 gr. of filver.Hence the amount of filex was 2^79.5 grs.

7. Bifmuthic Silver ore.

Having previoufly afcertained by roafting thatthis ore contained fulphur but no arfenic, andhaving obtained by cupellation from the roafledore 11. x 6 per cent, of filver, the analyfis wasthus conducted.

a. 300 grs. were digefted firft with 3 oz.of nitric acid and I oz. of water, and afterwardswith 1 oz. of the fame acid and |oz. of water:178 grs. remained undiffolved.

b. The nitric folution being concentrated tothe cryftallizing point was poured into a largequantity of water, a white powder was thusobtained which proved to be oxyd of bifmuth,and weighed 44.5 grs.

c. To the filtered liquor was added muriaticacid as long as any turbidnefs enfued. Theprecipitate thus procured was then digefted inmoderately flrong nitric acid, and there remain-ed behind 46. grs. of muriated filver.

d. The laft mentioned nitrous folution waspoured into water and afforded 32 grs. of oxydof bifmuth, which added to the other made up76.5 grs. equivalent to 62.2 grs. of metallicbifmuth.

e. The nitro-muriatic liquor was then eva-porated till cryftals of muriated lead began toform; fulphuric acid was then added, andevaporation was carried on till the whole be-came thick. The fulphat of lead thus obtainedwhen wafhed and dried weighed 19 grs.

f The refidue of the fluid was now fuper-faturated with ammonia, which threw downoxyd of iron, which, after being renderedmagnetic by roafting with wax in a coveredcrucible, weighed 14 grs.

g. Into the blue ammoniacal liquor wasplaced a bar of clean iron, by which 2 grs. ofcopper were precipitated.

a' * n ^ u ^le refidue ( a ) being ignited

loft 27-5 grs. which were fulphur. The re-mainder was boiled firft with 3 oz. and after-wards with x .5 oz. of muriatic acid. Thisfolution being evaporated to the cryftallizingpoint and then mixed with fulphuric acid,depolited by evaporation 89. grs. of fulphated

lead, which added to the 19. grs. in procefs (e)is equivalent to 76. grs of reguline lead.

i. The refidue, infoluble in muriatic acidconfifted merely of the quartzofe matrix of theore, and weighed after ignition 70. grs.

§ 3. Reduction of Ores.

Although it appears from the account whichwe have given of the ores of this metal thatmany of them when pure are very rich andmixed with a fmall portion comparatively ofother metals, yet the value of filver is fo muchgreater than that of any other, excepting gold,as to make it well worth while to work as filverores, thofe which contain only a very minutequantity of this precious metal. Hence it isthat in practice the filver ores contain a muchlarger proportion of foreign matters than thofeof the inferior metals do, and will allow ofbeing fubjected with profit to much moreexpenfive proceffes than can be employed forthe reduction of the others.

All the different methods that are ufed maybe arranged under two heads, namely, 1. Themethod by fufion. 2. That by amalgamation.We fhall begin by defcribing the moft Ample ofthe former, and proceed to the more complex.

ReduElion by Fufton.

1. We have already mentioned under thearticle Lead , that galena, or the native fulphu-ret of this metal, generally contains a portion offilver. Not unfrequently this latter ingredientis in fufEcient plenty to make its feparationfrom the lead a profitable undertaking. Thefmalleft proportion of filver which it is worthwhile to be at the trouble of extraditing cannotbe laid down with much accuracy, dependingas it does on the market price of filver, of lead,of fuel, of labour, &c. We apprehend thatin this country it will fcarcely anfwer with anylead that contains lefs than 12 oz. in the ton.It is obvious that the richer the lead is in filverthe better is it able to pay for any extraordi-nary care in its preparation, and of the moreconfequence it becomes to extradf from the ore-as great a quantity of metal as pofiible, even atan expence which mere lead would be unableto fupport.

Argentiferous galena when raifed from the ■mine, is generally mixed with a larger propor-tion of ftony matrix than common galena, be-caufe in confequence of the filver which it con-tains it is worth the miner’s while to workmuch fmaller and poorer veins of ore, than if