ORES. 
314 
Order XV. Cobalt. 
t . Alloys. 
2. Sulphurets, 
3. Oxides. . 
4. Salts. 
Order XVI. Manganese . 
1. Oxides. 
2. Salts. 
Order XVII, TmigsicnC 
1. Oxides. 
Order XVIII. Molybdenum. 
1. Sulphurets. 
Order XIX. Uranium. 
1. Oxides. 
Order XX. Titanium. 
1. Oxides. 
Order XXI. Chromium. 
1. Oxides. 
Order XXII. Columbium. 
1. Alloys. 
Order XXI II. Tantalum. 
L Oxides. 
Ores, analysis of. r \ lie diversity of me- 
tallic ores is so great, that no general method 
of analysis can be given. We shall there- 
fore follow the different orders, and point 
out the proper method of analysing each. 
In the rules ' we shall follow Bergman, ro 
whom we are indebted for the first precise 
treatise on the analysis of ores, except when 
his methods have been superseded by the 
improvements of succeeding chemists. 
Gold ores. The presence of gold may 
easily be detected by treating the mineral 
3 osed to contain it with nitro-muriatic 
and dropping muriat of tin into the so- 
lution. If the solution contains any gold, a 
purple precipitate immediately appears. 
Native gold ought to be dissolved in nitro- 
muriatic acid : the silver, if any is present, 
falls to the bottom in the state of muriat, and 
inay be separated by filtration, and weighed. 
Pour sulphat of iron into the solution, and 
the gold is precipitated in the metallic state. 
'Fhe copper, if any is present, may be preci- 
pitated by means of a plate of iron. The 
presence of iron may be ascertained by 
dropping tincture of nytgalls into a portion 
of the solution. 
The auriferous pyrites may be treated with 
diluted nitrous acid, which dissolves the iron, 
and separates the sulphur. The gold remains 
insoluble, and is found in the state of small 
grains. 
Ores of platinum. Proust’s method is, 
first to separate the sand with which the 
grains of platinum are mixed, by exposing 
them to a blas,t of air. By heat he evapo- 
rates the mercury, which still adheres to 
them, and then picks out the grains of gold, 
which are always mixed witli platinum, and 
which are thus rendered visible. The ore 
is then dissolved in an acid, composed of one 
part of nitre, and three parts of muriatic acid. 
A black powder remains. This powder, 
when roasted, gives out phosphorus and sul- 
phur. After this it is dissolved by nitro-mu- 
riatic acid, except a small residuum, which is 
plumbago. The solutions are then to be 
mixed. They consist of muriats of platinum, 
and oxymuriats of copper and iron. By eva- 
porating till tiie liquid when cold assumes a 
consistency greater than honey, and inclining 
the retort, the oxymuriats run off, and leave 
the muriat of platinum, which may be ob- 
tained pure by repeated solutions and crystal- 
lizations. The solution containing the mu- 
riats, and perhaps also a little platinum, is to 
be, diluted with a great proportion of water, 
and pure ammonia dropt in. 'Fhe red oxide 
of iron precipitates, and may be estimated by 
weighing it. When the Solution is somewhat 
concentrated, ammonia precipitates the pla- 
tinum in the state of a triple salt; and the 
copper, which now only remains, may be 
precipitated by a plate of iron. 
Ores of silver. The analysis of the ores 
of silver lias been always considered as very 
important, on account of the great value of 
the metal which they contain in greatest 
abundance. 
1. Native silver is to be dissolved in nitric 
acid. Fhe gold, if the ore contains anx, re- 
mains in the state of a black powder^.. -and 
may be dried and weighed. The silver may 
be precipitated by common salt. One hun- 
dred parts of the precipitate dried denote 
about seventy-live part s of silver. The pie- 
sence of copper may be ascertained by the 
greenish-blue colour of the solution, and bv 
the deep-blue colour which it assumes on 
adding ammonia. The copper may be pre- 
cipitated by a plate of iron, or by ’ the rules 
laid down hereafter. "When the ore contains 
arsenic, its proportion may be estimated by 
weighing before and after fusion ; for the ar- 
senic is dissipated by heat, or the ore may be 
dissolved as before hi nitric acid, which acidi- 
fies the arsenic. After the separation of the 
silver, the arsenic acid may be precipitated by 
nitrat of lead, 100 paits of the dry precipitate 
indicating about 22 of arsenic. 
2. Alloy of silver and antimony is to be 
treated with nitric acid, -which dissolves the 
silver, and oxidizes the antimony. .The sil- 
ver is estimated as above. The oxide of an- 
timony may be reduced by fusion with four 
times its weight of black" flux and a little 
soap. 
3. Sulphuret of silver is to be treated with 
diluted nitric acid, which dissolves the silver, 
leaving the greater part of the sulphur un- 
touched. The residuum is to be dried, and 
then the sulphur burnt off. The loss -of 
weight gives the sulphur. The residuum, if 
any, is undecomposed sulphuret, to be treat- 
ed as at first. M he silver is to be precipitated 
by common salt ; and the other metals, if any 
are present, may be ascertained as above. 
Part of the sulphur is always acidified. The 
acid thus formed may be precipitated by ni- 
trat of barytes, 100 parts of the dried precipi- 
tate indicating about 1 4.5 of sulphur. 
4. Autimoniated silver ore was analysed 
by Klaproth in the following manner: 100 
parts of it were boiled in diluted nitric acid. 
'Fhe residuum, washed and dried, was 26. 
These 26 were digested into nitro-muriatic 
acid. 4’he residuum now weighed 13 (so 
that 13 had been dissolved), 12 of which 
were sulphur, and burnt away, leaving be- 
hind them one part of silica. The nitro- 
muriatic solution, when -diluted largely with 
water, let fall a precipitate which weighed 13 
{or 10 of pure antimony), and had the pro- 
perties of- oxide of antiomony; for they did 
not evaporate till heated to redness, but at 
that temperature were dissipated iu a grey 
smoke. 
The nitric solution was green. Common 
salt occasioned a precipitate which weighed 
*>7.75, equivalent to 65.8.1 of pure si.ver. 
After the separation ot this muriat of silver, 
sulphat of soda occasioned no precioitate. 
therefore the solution contained no lead. 
When supersaturated with soda, a grey pre- 
cipitate fell, weighing five parts. On-burn- 
ing coals this precipitate gave out an arse- 
nical smell. It was redissolved in nitric 
acid ; sulphurated alkali occasioned a smutty 
brown precipitate ; and prussic alkali a Prus- 
sian blue, which alter torrefaction was mag- 
netic. Ifence he concluded, that these five 
parts were a combination of iron and arsenic 
acid. 
4 he nitric solution which had been super- 
saturated with ammonia was blue ; he there- 
fore suspected that it contained copper. To 
discover this, he saturated it with sulphuric 
ncid, and put it into a. polished plate ot iron. 
The quantity of copper was so small, that 
none c ould be collected on the iron. 
5. Sulphuret ot silver and copper max be 
analysed as No. 3. separating the copper by 
means of a plate of iron. 
6. Black silver ore may be analysed as No. 
2. separating the copper", if any is present, by 
means of an iron plate, and estimating the 
carbonic acid that escapes when the cue is 
heated or dissolved in nitric acid. 
7. Red silver was analysed by Vauquelin 
in the following manner: one hundred parts 
of it were digested in 500 parts of nitric acid 
previously diluted with water. The undis- 
solved residuum, being washed and dried, 
weighed 42,06. Being treated with muriatic 
acid, it was all dissolved except 14.66 parts, 
which were sulphur. The muriatic solution’ 
when diluted with a great quantity of water, 
deposited a white -powder, which weighed 
21.25, and was- oxide of antimony. The nitric 
acid solution remained still to lie examined. 
Muriatic acid occasioned a heavy precipitate, 
which weighed 72.66 parts, and which was 
muriat of silver. Reagents shewed that the 
acid retained no other substance of solution. 
8. Muriat of silver was analysed by Klap- 
roth :- one hundred parts- of it were mixed 
with thrice their weight of pure carbonat. of 
potass, and melted together in a glass retort. 
The mass was dissolved in water, and tiie so- 
lution filtred. A residuum remained, which 
was dissolved in nitric acid, with the excep- 
tion of a red powder, which, treated with 
nitro-muriatic acid, was dissolved, except a 
little muriat of silver, which, when reduced, 
yielded .5 of pure silver. Ammonia precipi- 
tated from the nitro-muriatic solution 2.5 
parts of oxide of iron. The nitric solution 
was precipitated by common salt; the muriat 
of silver, thus obtained, yielded, when re- 
duced, 67.25 of pure silver. 
The original aqueous solution of the alka- 
line mass was saturated with acetous acid, on 
which it deposited 1.75 parts of alumina. 
'Fhe solution was evaporated to dryness, ami 
the dry mass treated with alcohol, which 
dissolved the acetite-of potass. The resi- 
duum, amounting to 58.75 parts, was dissolv- 
ed in water, and being treatedwilKmuriat of 
barytes, 15 part- of sulphat of barytes pre- 
cipitated, indicating the presence of "about .5 
of sulphuric acid, or 0.75 sulphat of potass. 
The remaining 58 parts were muriat of po- 
tass, indicating about 21 parts of muriatic 
acid. 
