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Cyanide ProcesfM. 

lamo, cloth, $ 

The Chlorinatlon ProceM. 

lamo, cloth, $1.50. 

Practical Mine VentlUtlon. 

For the Use o( Mining Engineers, Students, and 
Practical Men. With plates. z6ino, cloth,* 

Hydraulic and Placer Mining. 

With illustrations, including full-page half-tones, 
lamo, Yi -^ 934 pages, cloth, $2.00. 





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London: CHAPMAN & HALL. Limited. 

1907. y/ 

,3^-5;^ V 

• •*-*- By ** *- »* »« 
E. B. WIL$ON.^_. , .. 


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The treatment of refractory gold-bearing ores Is 
of interest to those who are or have been engaged 
in mining the precious metal. 

Some wise person has stated " that all is not gold 
that glitters " ; and if he were alive and a miner he 
could have added two other facts which history has 
establishe^;Jyiz. V •• . .■ ; 

That all goUUbsaring crocks do not contain gold in 
paying quantfties; also, that some gold-bearing rocks 
contain considi(3.t:lc quantities of gold, but are com- 
mercially valueless. 

The greater part of the money sunk in gold-min- 
ing ventures has been due to the above facts; but 
should the statement be discredited, inquiry of those 
who have lost money in the past will substantiate it, 
we believe. 

The chlorination method of treating refractory 
ores has been some years before the public, and 
while old yet it is new. 

It has added much to the world's store of gold. 



and is destined to add more as it becomes generally 
practised, as it has assumed a place in metallurgy 
from which it cannot be dislodged. 

The process is not oiie of great difficulty, although 
it has been belittled by those who, claiming to be 
mining experts, were unable to practise it, and who 
therefore proposed either a less economical plan of 
treatment, or brought financial loss upon those who 
followed their advice. The writer takes occasion 
here to express his obligations to those whose data 
he has included in this volume, and trusts he has 
given them proper credit. _ 

The author recognii'6&'H^f (|filrrfes as well 
as students and those practicall];;eng3ged are inter- 
ested in this subject. He'"hdS'erfdeay6red for that 
reason to place the subJ&t/ih-'eujIJ'^ffpjJTi that any 
one who reads can understand. The chemical 
formulae are of little value except to those who are 
in practice or intend to practise; their omission 
would, however, detract considerably from the value 
of the book for reference and completion of the 

The author trusts his endeavors will meet with the 
approval of those interested. 

E. B. Wilson, 
juNB, 1897. 




I. Lixiviation by Chlorine Solutions •••••••••••••• i 

II. Preparation of the Ore IX 

III. Roasting the Ore 20 

IV. Roasting furnaces •••••• • 36 

V. The Leaching Process 60 

VI. Filtering 75 

VII. Precipitation • 81 

VIII. Refining Precipitates 92 

IX. R6sum6 of Chlorination and Plant q8 

X. Cost of Chlorination X05 




LIXIVIATION is the term applied to the abstraction 
by a liquid of the soluble part of a mineral, or aggre- 
gation of minerals. An aggregation of minerals is a 

Lixiviation is therefore the abstraction by a liquid 
of the soluble part of a rock. 

The useful processes for separating gold from ores 
by lixiviation are limited chemically by the few 
known solvents for it, and commercially by the cost 
required to effect profit. We are therefore at present 
confined to the following processes: 

Lixiviation by hyposulphite soda solutions, or the 
Russell Process, for silver first; 

Cyanogen solutions; 

Bromide solutions; 

Bromide-cyanogen solutions; 

Chlorine solutions. 



They are all based upon the solubility of gold in 
aqueous solutions of the chemicals named. Lixivia- 
tion by chlorine solutions is wTiat we are particularly 
to deal with. Rose, in his " Metallurgy of Gold," 
gives as the relative dissolving powers of the last 
three chemicals in i-per-cent solutions, with each 
solution at the temperature of 60° Centigrade, the 

Chlorine in \\ hours dissolves 4-49!^ of gold. 

Bromine " li " " 6.46;^ " " 

Cyanide " \\ " " 0-57!^ " " 

All these wet processes require that the ore be 
subjected to preliminary treatment before using the 
solutions. With chlorine solutions preliminary treat- 
ment is elaborated more than in the bromine or 
cyanide solutions. 

All four processes seem to occupy a distinctive 
iield of their own, but also encroach upon each other's 
territory. In such cases the choice of the process 
should depend upon which will extract the greatest 
percentage of gold at the least cost. 

Could we say that any one of the processes was 
the best, this choice would be an easy matter; but as 
each ore differs in character, it is not possible to say 
that any one of the above processes is the best under 


all circumstances; and then the choice of process 
becomes difficult, and can only be decided by the 
metallurgist after experiment. 

Chlorination (by which we mean the leaching of 
gold ores by chlorine solutions). does not save the 
silver content of the ore, because during preliminary 
treatment the ore is subjected to chloridizing roast- 
ing, which forms an insoluble compound in water, 
known as Silver Chloride. 

The reverse is the case with gold, which forms in 
chloridizing roasting a gold chloride soluble in water. 
But other metals may do the same; consequently it 
becomes necessary to remove the other metals by 
oxidation, or by oxidizing roasting. 

Under certain conditions gold unites with chlorine, 
forming the gold chloride known as trichloride of 
gold, or auric chloride, where one triad atom of gold 
unites with three monad atoms of chlorine, forming a 
molecule of auric chloride whose molecular weight is 
302.31, and whose chemical symbol is AuC!,. The 
chief source of chlorine is common salt (NaCl), which 
contains about 60 per cent of this substance. As a 
gas it has a greenish yellow color and a very dis- 
agreeable odor, producing on inhalation a suffocating 
cough, (The cough may be relieved by breathing 
ammonia or ether.) 

Cold water absorbs about twice its volume 




chlorine gas, being converted gradually into hydro- 
chloric acid (HCl) by the chlorine uniting with the 
hydrogen of the water. 

Slaked lime,- or calcic hydrate (CaO + H,0), when 
exposed to chlorine gas forms a chloride of calcium 
and hypochlorite of calcium, or what is known as 
bleaching-powder, with formula CaCl^ + CaCI,0,. 

Commercial bleaching-powder contains from 20 to 
F 35 per cent of available chlorine. It forms a homo- 
' geneous white powder, possessing a smell of hypo- 
chlorous acid, gradually becomes moist on expos- 
ure to the air and decomposes with absorption of 
water and carbonic acid. It should therefore be 
kept away from the atmosphere. Bleaching-powder 
derives its chief value from the hypochlorite of lime 
which it contains. 

Hypochlorous acid is so weak an acid that its salts 
are easily decomposed. Carbonic acid gas decom- 
poses it readily. The salts of hypochlorous acid are 
unstable compounds, the same as the acid; and the 
calcium hypochlorite gives the bleaching-powder its 
chief value botlj for bleaching and the chlorination 
process, from the fact it yields its chlorine readily. 
When either hydrochloric or sulphuric acid are added 
to bleaching-powder a quantity of chlorine equal to 
the quantity in the hypochlorite is evolved. The 
reaction is as follows: 


( 2HCI + CaCl.O, = 2HOCI + CaCl,; 
' J2HC1 + 2H0C1 = 2H,0 + 2C1,. 

( CaCI,+CaCl,0,+H.S0.=2CaS0.+2HCl + C1,0,; 
■ 1 2HCI + CI,0, = 2H,0 + 2CI,. 

In the first case half the chlorine is obtained from 
hypochlorite and half from the hydrochloric acid. 

In the second case the sulphuric acid decomposes 
the chloride and hypochlorite, liberating all the chlo- 
rine in both compounds. 

It may be possible to obtain liquid chlorine in a 
concentrated state, thus reducing the bulk compared 
with bleaching-powder. To dissolve gold by chlo- 
rine, the latter must be in a free or nascent state, that 
is, as a gas, or in a liquid state, uncombined with 
other chemicals, as chlorine water. The gold must be 
in a metallic state, and the chlorine will then combine 
with it if oxygen be present. Whenever metallic 
gold is dissolved in nitro-muriatic acid (HNO, -j- HClJ 
chlorine is liberated in the presence of oxygen, and 
forms with gold the compound HAuCl, + 2H,0, 
known as chlo-auric acid, a very peculiar combina- 
tion, the reaction of which is as follows: 
4HCI + CaCi.O, + Au + HNO, = 

HAuCl. + CaCl, + NO, + zH.O. 

The deep yellow solution obtained gives upon 
evaporation yellow crystals of the double chloride of 


gold and hydrogen (HAuCl,), and this cautiously 
heated solidifies to a red crystalline mass, soluble in 
water, alcohol, or ether, and is auric chloride, AuCl,. 
The dissolving of gold from ores by the above proc- 
ess would not be feasible on account of dissolving 
other impurities as well, together with the subsequent 
difficulties and expense in separating the gold from 
the base impurities, and it is merely mentioned as an 
, example of the active principle of chlorine in its 
I attack upon gold when it can be liberated from its 

It can be liberated from its compounds as readily 
as in the above example. The practical results, how- 
ever, depend upon its liberation in contact with gold, 
in aqueous solutions, free from impurities, whereby 
its usefulness may not be impaired, and from which 
the auric chloride formed can be precipitated. 

Plattner in 1856 proposed what is now known as 
the Plattner system of chlorination, which he accom- 
plished successfully by the following steps: 

1. He subjected the ores to a roasting process for 
the purpose of oxidation, and driving out of the ore 
those substances which would be acted upon by free 

2. He leached the roasted ores with water, the 
ores having been previously saturated with chlorine 


3. He precipitated after filtration the auric chloride 
thus formed in the second step by means of ferrous 

The foundation for the chlorination process of 
i to-day was thus built, and whatever improvements 
have been made are along the lines adopted by 

It is often necessary, in treating sulphides contain- 
ing iron and other base metals, to chloridize and 
roast as well. This is especially necessary with such 
ores as contain much sulphur, arsenic, antimony, or 
other such volatile compounds which should be dis- 
placed, and which simple oxidizing roasting will not 

For chloridizing roasting, common salt (NaCl) is 
mixed with the ore (as explained under the heading 
Roasting, p. 20), converting those substances not 
volatilized into soluble and insoluble chlorides. 

Chlorine has a remarkable tendency to act on 
metals and the oxides of metals, and so long as 
volatile substances are combined with a metal during 
roasting very little chlorine escapes; but after these 
are displaced by heat and chlorine the chlorine itself 
escapes — and this is peculiar, since chlorine is very 

Due observations made relative to the amount of 
ff volatile matter in an ore, and the affinity between 


chlorine and that substance, allows us to advance one 
step nearer the recovery of gold by chloridizing 
roasting than by oxidizing roasting. 

In the present state of the art we cannot treat ores 
by wet processes as they come directly from the 
earth; or could ores be subjected to treatment with' 
out roasting for chlorinating, they would be more 
readily treated by some cheaper process ; conse- 
quently preliminary treatment is a necessity. Again; 
the chief object of chlorination is to recover gold 
from refractory ores where cheaper processes will not, 
We therefore find chlorination practised upon sul- 
phides, telluridcs, arsenides, and other similar ores 
whose combination of substances can be broken by 
oxygen or chlorine with the assistance of heat. As 
these minerals form but a small proportion of the ore, 
they are concentrated to reduce the bulk before 
treatment, and thus save waste in time, fuel, chemi- 
cals, and capital. Concentration may follow amalga- 
mation unless the pre be too refractory, but in either 
case crushing of some description is preliminary to 
concentration and subsequent chlorination. The 
foregoing brief description of the object sought will 
allow the reader to follow intelligently the process, 
which should proceed as follows: 

I. Preparation of the ore. 


3. Roasting appliances. 

4. The process. 

5. Filtering. 

6. Precipitating. 

7. Refining. 

8. The cost of treatment. 
g. The plant required. 

Under the above headings may be introduced 
details not of minor importance, for the attention to 
details has perfected the process to its present condi- 
tion of usefulness. 

Precious- metal mining has reached the stage where 
capital invested judiciously will as surely bring 
returns as any manufacturing business where equal 
care is exercised. The difficulties formerly encoun- 
tered are to a very great extent overcome, and 
chlorination is but one of the improvements in that 
direction. We do not mean to convey the idea that 
all difficulties are circumvented, nor do we mean to 
convey the idea that lixiviation is able to do more 
than assist in recovery of gold, and we particularly 
advise parties intending to enter into gold-mining to 
beware of low-grade milling propositions which carry 
' less than Sio per ton of gold where chlorination is to 
be practised. 

While low-grade bodies of ore are more uniform 
and continuous than " bonanzas," there is a limit to 


their*' low-gradeness, " especially if refractory. That 
one low-grade mining company with a large mill is 
able to treat its ore at a good profit is no criterion 
that another large mill in a different locality can 
treat the ore in that locality at all. We advise in 
all mining enterprises the consultation of trained min- 
ing engineers, practically, scientifically, and techni- 
cally educated. 



Were the whole mass of ore to be treated by 
chlorination as it ' came from the mine, it would 
be economy to crush the ore dry preliminary to 
roasting. The treatment of such large masses of 
ore would require an immense outlay of capital for 
chlorinating purposes, together with increased size 
of the plant in general. For instance, if but one 
tenth of the ore carried mineral, the mechanical 
arrangement would require to be ten times as large 
as where the mineral had been concentrated; larger 
supplies of chemicals and fuel would also be needed. 
There are rare instances where clean silicious ores 
could be treated in this manner, but where they 
occur once, the probabilities are they do not occur 
again in ten thousand instances. 

The ore, that is, the vein rock containing mineral, 
is mined, cobbed, assorted, loaded into suitable con- 
veyances and transported to the mill, as the first step 

in preparation. In some instances the vein rock 



will not show mineral, but it is there; and in such 
instances the rock must be treated with the mineral 
streak, provided it carries gold. Vein rock between 
the hanging and foot walls very often is totally bar- 
ren, and again will carry more precious metals than 
the mineral streak proper. To avoid wear and tear 
upon the machinery in the first instance, and to avoid 
loss in the second, judicious assays should be made 
and recorded of all vein matter broken in the mine. 

When the ore reaches the mill, it is unloaded over 
a chute which has an hiclination of 40° and upwards. 
This chute has for its floor in some part of its length 
a number of iron bars, separated by spaces, to allow 
the finer ore as it comes from the mine to pass 
through to the rolls, while the coarser passes over 
the bars into the rock-crushers, and from the latter 
to the rolls. These screen-bars are termed " griz- 
zlies," and assist the crushers very much by their 
separating material already fine enough for the rolls, 
which would otherwise interfere with the amount of 
ore crushed in the rock-breakers. 

The most suitable rock-crushers are of the Blake 
and Gates type. 

The former has been longer in use, so that by 
some it is considered to be the only crusher of 
moment. The largest size of the Blake we believe 
is No. 20, with an opening to receive rocks 13 X 30 


inches and under, which it can crush to sizes of i^ to 
if inches in diameter. The capacity given is lo tons 
per hour, which it only reaches under most favorable 
circumstances. A fair average of its capacity would 
probably be 8 tons per hour. 

The Gates crusher with the same horse-power can 
crush double this amount in the same time. Against 
the Gates crusher is its weight, and while it crushes 
more it wears more. 

For fine crushing, two small crushers are better 
than one large crusher, as setting the jaws to crush 
fine hinders the amount of product which can pass 
through. However, in small machines the opening or 
mouth for the reception of the rock is smaller, and 
would require finer ore, possibly sledging, in order to 
feed; consequently a large crusher, assisted by two 
smaller ones to receive its product, would do the most 
economical work, 

Mr. Blake puts the limit of economy in the use of 
multiple-jaw crushers at No. lo screen (lOO holes to 
the square inch). If rolls are to be used, and then 
stamps, there is not .so much saving in crushing fine 
by rock-breakers as would appear, as all ore must be 
thoroughly dried; and if lo-mesh screened ore were 
admitted to the stamp battery the coarse sand would 
simply pack, and the agitation necessary to keep the 
ore stirred up in the mortar would be lacking. For 



the above reasons multiple-jaw crushers for fine 
crushing can be dispensed with in most cases where 
rolls and stamps are used, and the jaws of the 
crusher set to size of ore which will work well in the 
rolls. It is advisable to use crushers whenever possi- 
ble to reduce the ore for the rolls, say to \\ inches 
diameter, and have the rolls crush this to, say, J- inch 
diameter before admitting to the stamps. In this 
way the product of the stamps may be increased. 

The rolls mentioned are cylinders with steel tires 
turning towards each other, the ore passing between 
them. They are set close, with heavy springs or 
swinging pillow-blocks so arranged as to give if 
necessary to allow large pieces of rock or a coupling- 
pin or piece of drill steel from the mines which has 
found its way into the ore to pass through without 
breaking the rolls. They are also in some cases 
fitted with magnets to attract any iron or steel which 
would dent the faces of the rolls. ' 

It was formerly customary to gear these rolls, but 
that added to the wear and tear; they are now 
almost universally run by pulleys and belts. If the 
ore which passes the rolls is not sufficiently crushed, 
it is screened and returned to the rolls for recrushing 
with an additional supply from the crushers. 

It is at times feasible to crush fine enough with 
crushers and rolls to chlorinate without stamp-milling. 


For this purpose, however, we must have an easily 
pulverized rocV, and return all the product which 
docs not pass the desired screen. When the rock is 
hard this method is destructive to screens, wearing 
them out quickly and requiring that the ore be free 
from moisture to pass the screen. For fine crushing 
the most satisfactory arrangement is the stamp-mill, 
especially if amalgamation is to be practised before 

The action of these crushing-machines is mashing, 
and they do not round the particles of ore as do 
certain classes of pulverizers which pulverize by abra- 
sion. The latter class are not suitable for gold or 
silver milling, as they do not crack the grains of ore 
in a proper manner; however, when roasting is to 
precede the process this matter is not of such moment 
as for amalgamation or cyaniding. The Huntington 
and Chilian mills are also excellent crushers in place 
of stamps. 

If free silver be present in the ores, chloridizing 
roasting followed by amalgamation may be practised, 
or the ore treated first to recover the gold by chlori- 
nation and afterwards by hyposulphite of soda to 
recover the silver, or the reverse; but there must be 
in each case silver values greater than gold. Roasted 
gold ore does not amalgamate readily, while silver 
gives good results. ' Another consideration is that 



there will be a loss of gold if that be not treated firsl 
as it is generally customary to add chemicals t 
brighten the mercury, which becomes sickened whei 
roasted ore is amalgamated. 

We can therefore consider all silver lost wher 
chlorination is practised or a good portion of the gol 
lost where silver is recovered first. 

The ends in view will determine the crusher to b 
used. Coarse crushing may be possible, and whiJ 
objectionable for good roasts and clean concentrate: 
has advantages over fine crushing, which is alway 
attended with considerable fine ore and slimes ver 
inconvenient in filtering or drainage to wet processes 
With chlorination, however, this drawback is some 
what removed by concentration of the ore, and th 
subsequent roasting which follows, changes the shap 
of the mineral particles from compact to porous 
thus facilitating drainage and leaching. 

The crushing process is followed by concentration 
that is, a separating of the mineral from its gangue c 
vein rock not containing mineral. These concer 
trates are usually sulphurets of some descriptior 
which make the ore refractory, and thus necessitat 
chlorination; in fact, the usefulness of the proces 
hinges upon this class of ores. 

To concentrate the tailings from the crushers the 
are conducted to jigs, where they are washed fre 


from slimes. The sands and lighter particles are 
carried from the jigs to vanners, buddies, bumping- 
tables, or other similar arrangements. These ma- 
chines, by the aid of water, separate the lighter par- 
ticles of sand from the heavier particles of mineral: 
the former are washed away, while the latter are 
collected. It may not be necessary to jig in all 
instances, but it is better to do so where large quan- 
tities of sand might otherwise go to the tables, and 
there interfere with the work. When fine crushing 
is practised from 40 to 60 mesh screen (i.e., 1600 
or 3600 holes to the square inch respectively), from 
30 to 60 per cent of the product is slimes, and unless 
these are separated from the sands and concentrated 
separately, they will be lost. To accomplish this the 
ore is separated into fine and coarse, each carrying 
values. This product is now carried to jigs, which, 
having more even sizes to deal with, are able to treat 
with a greater degree of certainty. The surplus 
products of the jigs then go to the tables — the coarse 
to one, the fine to another. This order may be 
somewhat varied, but it is absolutely necessary for 
chlorination that the concentrates should be clean, to 
give the best extraction results and the least loss of 
values in concentration. Slimes will adhere to the 
sands unless sufficient water is used to separate them ; 
and as they usually are rich in precious metal, if the 




appliances mentioned do not answer, tliey sliould b 
run into settling-tanks. 

The cost of the preparation of ore is against thi 
use of chlorination at times, but the main choice o 
a process is, other matters being equal, the value; 

If we take, for example, an ore carrying 2 oz. 

I'gold ($40}, with 16 oz. of silver ($9.60), we may save 
95 P^i" cent of the gold and lose all the silver: in 
money this loss is $12. oS. If by cyaniding we 
recover 90 per cent of both values, the loss amounts 
to $4.96; our choice would therefore naturally be tht- 

1 use of the cyanide process. If now we take a $40 
gold ore with no silver value, the loss by chlorination 
with 95 per cent recovery would be $2 against S4 by 
the cyanide recovery of 90 per cent. The choice 
then narrows down to the question; can chlorination ; 
be practised as cheaply as cyaniding upon a given j 
ore ? No direct answer can be given, since chlorina- j 
tion has more preparation of ore to contend with, ' 
and if in our example the margin of $2 is consumed 
by the extra manipulation of the ore, cyaniding would 
be the best. (See Cost of Treatment.) There is a '• 
limit where the difference in favor of cyaniding upon \ 
strictly gold ore occurs, which is that point where the 
extra expenses of chlorination are counterbalanced 
by increased extraction. For instance, in an $80 gold 


J ore with 95 per cent extraction there is a difference 
of $4 in favor of chlorination, which is amply suffi- 
cient to favor its use in preference to cyanide extrac- 
tion in most instances. 



Having obtained the mineral in the ore as coH' 
centrales, by the preparation noted in the preceding 
chapter, our attention must be directed to freeinf 
that mineral from the base metal compounds which i 
contains. To accomplish this we have recourse t« 
oxidization, which in our case is the application o 
heat with oxygen present in sufficient quantities t( 
unite with the base metals, forming oxides of metalf 
which volatilize. 

Where air only is requisite for the purpose, the 
roasting is termed " oxidizing roasting," but where 
other substances must be employed to assist decom- 
position, such as common salt, the operation is termed 
" chloridiiing roasting." 

The chlorine from the salt (NaCl) seems to answer ' 
a twofold purpose, since it assists not only oxidation, 
but forms combinations with metals which volatilize 
or else become insoluble.* To roast thoroughly, the 

•Seep. 7. 


ore should not be subjected to a high heat at the 
commencement of the operation: in fact at no time 
should it fuse or melt, but the heat may be increased 
towards the close of the roast. 

If we allow fusion in roasting we cannot attain our 
object, for it is next to impossible to separate some 
substances, such as iron and sulphur, which have 
become united by heat, and no substances which 
have fused are as susceptible to oxidization as before, 
while its action or destruction of the leaching com- 
pounds are nearly as great as when they were in the 
raw state. 

Certain substances admit of oxidization and will 
volatilize to a certain point, after which it becomes 
almost impossible to oxidize them more; at this stage 
chlorine assists on account of its great affinity for 
metals, and still further reduces the amount of the 
remaining impurities. 

Yet with the assistance of chlorine it is not possi- 
ble to free some metals from impurities such as iron 
sulphides. The greater quantity of sulphur is readily 
volatilized, but the last 2 per cent of sulphur from 
an ore containing above lO per cent sulphur will 
require as much labor, care, and expense, if not 
more, than the first 8 per cent, 

When sulphur has been removed to the lowest 
limit, which is about one quarter of one per cent, the 


ore is said to be " roasted dead," since it is in such a 
condition that we cannot further reduce it without 
great expense, and is practically in such a form its 
injury to the leaching process can be tolerated. 

The affinity of sulphur for other substances than 
oxygen modifies the process of roasting somewhat, as 
is seen where chlorine in the presence of hot silver is 
reduced to silver chloride, or where, when arsenic is 
to be evaporated, carbon is added to the mixture, 
producing a combination more easily evaporated than 
the oxide. 

Chloridizing roasting deals chiefly with sulphur 
compounds, with the object in view of freeing the ore 
from that compound; no doubt there will be met in 
practice other difficult substances to be eliminated. 
It must be borne in mind that roasting is not melting, 
and that the latter must be avoided if it be the object 
to accomplish a good roast, and high extraction by 
chlorination. The following substances are of fre- 
quent occurrence, consequently their action in roast- 
ing is worth consideration. 

Iron cannot by any means be freed entirely from 
sulphur. Roasting will reduce it to about 8 per 
cent, chloridizing roasting to about 0.25 per cent, at 
which point eHmination ceases. 

Sulphide of zinc (zinc blende) is slow to oxidize, 
and is not purified of all its sulphur. It further vola- 


tilizes freely, and carries off the precious metals asso- 
ciated with it when exposed to moderate heat. 

Copper sulphides can be readily freed from their < 
sulphur by slow roasting at a moderate heat, with or ] 
without salt. 

Tellurides act in a manner similar to zinc. , 

The sulphide of bismuth, being easily fused, is j 
difficult to oxidize, since it melts at a low tempera- I 

Galena is nearly as difficult to oxidize as bismuth , 
on account of its fusing at low temperature. 

Mercury and silver are readily liberated from ore 
by heat. The former, however, volatilizes at a low 
heat, and requires great care when roasting to avoid 
this. ' 

Mercury used to collect gold and silver as amalgam 
is retorted by volatilization and the fumes condensed 
in a cooled vessel without much loss of quicksilver. 

Silver is readily converted into silver chloride by 
roasting with salt. This salt is insoluble in water, 
but dissolves in solutions of hyposulphite of soda. 
The Russell process is based upon this fact. 

Sulphides of antimony are difficult to oxidize, 
because extremely fusible. 

The sulphides of nickel are easily oxidized, forming 
pure oxides. The same applies to cobalt. 

Arsenic sulphides are readily oxidiaed, both the 

he H 

arsenious and sulphurous acids forming volatile com- 

Phosphorus cannot be freed from iron by roasting; 
neither can titanic acid. 

Arsenic is also difficult to remove from iron. 

Fine ore roasts quicker and better than coarse; but 
ore not sized, that is, mixtures of coarse and fine ore, 
offer uneven surfaces to the action of heat and oxy- 
gen, one getting in the other's way, so to speak. To 
assist in exposing the various surfaces of the ore to 
the reagents, they are stirred or rabbled, either by 
hand as in plain reverberatory furnaces, or by fixed 
rabbles as in moving hearth-furnaces, or by movable 
rabbles as in the Spence furnace, or by falling from 
shelves as in revolving furnaces. This rabbling also 
performs another office: it avoids fusing, sintering, or 
melting of the ore during roasting by its agitation. 

The roasting ore, after moisture has been driven 
entirely from it by heat, becomes like so much quick- 
sand, flowing rather than hanging together in a pasty 

It is not always necessary that ore should be ex- 
tremely fine: in some instances such fine ore would 
be a hindrance rather than a help, since it would 
cause more labor in preparation, and greater care in 
roasting and also in filtering. The principle to be 
governed by, is to crush only to that coarseness which 



will roast readily, and yield the greatest per cent of 
gold to chlorine. The filtering is a secondary matter, 
for when once the auric chloride has been obtained 
in solution the goM may be recovered from it, even 
if time is long drawn out in the process. As noted 
under preparation of ore (p. i6), ores undergo a com- 
plete change in physical structure when roasted; they 
are also liable to be converted into n on- refractory 
ores; at any rate, they are not refractory to chlorine 
solutions. Mr. Daggett says; " The leaching of 
roasted ores is quicker done for any process than the 
leaching of raw ores, unless the soluble salts formed 
in roasting have received a prior leaching, when it is 
about the same as for raw ores." 

This is a measure true in chlorination, where some- 
times difficulty in filtering occurs when fine slimes 
prevent the passage of the liquor. In other leaching 
the ore packs to such an extent that it is next to 
impossible to drain at all, not more than a quarter of 
an inch per hour being recorded with raw ore, while 
with ores which do not form a clayey compact mass 
impervious to water filtration is comparatively rapid, 

Where the base metals present in the ore are in 
excess of the volatile substances, it may be policy to 
hasten oxidation by adding small quantities of iron 
pyrites, and allow the sulphur driven off to combi 

combine ^^| 


with base metals before adding salt for chloridizing 

Formerly it was thought necessary to have a cer- j 
tain percentage of sulphur in the charge for its effect 
in chloridizing. This, Mr. Briickner thinks, is a mis- | 
take. In his judgment the iron pyrites is added for 
volatilizing the arsenic and antimony, and for pre- 
venting the formation of arseniates and antimoniates 
of silver and gold which resist chlorination; very little 
sulphur, or, in its absence, quartz, is sufficient to 
evolve, when in contact with a very small percentage 
of salt, the chlorine necessary for chloridizing all the 
silver contained in the charge, after the arsenic and 
antimony have been driven off. Thus an addition J 
of from I to lo per cent of iron pyrites is in most | 
cases required for the success of the roasting process. 
Ores which are apt to cake at a low temperature are 
mixed with lo to 20 per cent of rich tailings. Ores 
containing lime and alumina have to be mixed with I 
silicious ores so that silica shall be in excess. (Dr, 
R. W. Raymond, A.I.M.E., 1885.) 

Ores containing considerable sulphur in them must 
have care to keep down the heat which the burning | 
sulphur creates, and salt should not be added at this I 
stage, since the heat of the burning sulphur may be j 
sufHcient to volatilize the chlorine and cause a loss ofM 
gold as well. When salt is added at the commence* ■" 



merit of a roast in the reverberatory furnace a loss of 
gold occurs, but not to so great an extent, and some- 
times not at all if the salt is added on the hot hearth 
or end of the roast with not more than two per cent 
of sulphur present. 

At the end of the roast soluble chlorides are formed 
as readily as when mixed with the ore at the com- 

Prof. Christy of the University of California ascer- 
tained that sulphides roasted without salt lost little 
of their precious metals, but that with 3 per cent salt 
added the loss in one instance was 30 per cent of the 
gold and 50 per cent of the silver. This very great 
loss he attributes to high temperature and the tellu- 
ride in the ore. 

Plattner from his experiments states " that loss of 
silver increases with the temperature in roasting, 
with the looseness or porosity of the ore, and the 
freedom with which silver combines with other sub- 
stances." " The loss also increases with time of 
roasting." He used artificial mixtures for his roast- 
ing tests to ascertain the volatility of gold, such as 
arsenides and sulphides. " His conclusions were, that 
a loss of gold can take place only in oxidizing roast- 
ing, when the operation is carried on so rapidly that 
fine particles are carried off mechanically." 

Prof. Christy and others coincide with him in his 




deductions with regard to oxidizing roasting, but add 
that " he does not seem to have been aware of the 
volatility of gold in chloridizing roasting," Kustel is 
said to have recorded a loss of 20 per cent of gold in 
oxidizing roasting of certain tellurides of gold and 
silver, attributing the loss to the volatilization of tel- 
lurium; and says: "If salt is present during roasting, 
the chloride of tellurium volatilizes, and it is possible 
that this volatilization causes gold to volatilize as 
well," Mr. C. H. Aaron, Prof, Christy says, was the 
first to publish anything definite on the losses of gold 
in chloridizing roasting. He pushed the roasting pur- 
posely with and without salt; the salted ore upon 
assay was found to contain but one half as much gold 
as the unsalted. 

Mr. C. A. Stetefeldt gives an account of his inves- 
tigations with chloridizing roasting, and found the 
losses to be from 42,8 to 93 per cent of the total 
gold. He also states " that volatilization of gold no 
doubt takes place with copper chlorides," but adds, 
as Mr. Butters' experiments show, " that copper 
chlorides are not essential to produce this loss," 
"Mr, C, Butters found that with gold ore free from 
copper no loss occurred in oxidizing roasting, but 
when chloridizing roasting was undertaken in a muffle 
with 5 per cent salt, there was a loss of from 68 to 85 
per cent of the gold." " He found also that an in- 




creased quantity of salt up to 10 per cent caused no 
increased loss of gold." 

Prof. Christy has shown by a large number of ex- 
periments, the results of which are published in his 
admirable paper contributed to the American Insti- 
tute of Mining Engineers,* that muffle tests with salt 
gave a higher percentage of gold loss when the salt 
was added at the end of the roast rather than at the 
commencement. This being the reverse of practical 
experience in continuous roasting, he accounts for it 
as follows: " Where batch roasts are made and the 
whole lot of ore is kept at the same temperature 
throughout (as in a muffle), when the gold chloride 
has once formed and left the batch of ore, that is the 
last of it. At the end of a roast more gold being 
exposed, the addition of salt produces a greater loss 
of gold." 

"In practice with continuous roasting, if the salt is 
mixed throughout the ore from the start, a continu- 
ous volatilization goes on and likewise loss, where, on 
the other hand, if salt be added at the finish, or hot 
end of the furnace, the long surface of unsalted cooler 
ore condenses the chloride of gold." " Part of this 
cooler ore is giving off sulphurous acid gas, and this 
with steam from the burning fuel offers excellent 

• Vol. XVII. p. 43, 

eni ^y 


means (or the reduction of chloride of gold in the 
furnace; but the most efficient means is in the pyrites 

The factors entering into " salt roasting " are salt, 
temperature, and time. 

The amount of salt necessary for a chloridizing 
roast will depend upon the amount of oxidation re- 
quired, and this must be governed by the ore. The 
less salt used the better, but enough must be used to 
drive off the sulphur and form silver or base metal 
chlorides; the leaching which follows will then give a 
high percentage of recovery. 

Aaron says that salt should be below 4 per cent. 
Butters, Stedefelt, and Prof. Christy, and the deduc- 
tions of others from practical work, bear out Mr. 
Aaron's statement. 

Four per cent of salt is equivalent to So lbs. to the 
ton of ore. That amount of salt is probably more than 
required for driving off impurities, and what cannot 
unite with impurities present will unite with gold to 
form gold chloride; but if more than sufHcient be 
present, chlorine, being readily volatile, will escape 
with loss of precious metal. A few tests with the ore 
will determine the percentage of salt most advisable 
for roasting with an ore. 

Temperature has been mentioned previously as oi 
importance in chloridizing roasting; we therefore rcj 



fer to it again. It is necessary iii continuous roasting 
that at first slow heat and low temperature should 
take place; as the ore moves forward towards the 
6re the heat increases from the burning sulphurous 
acid gas; when nearer to the fire, the sulphur fumes 
having ceased, the heat is increased. Had the tem- 
perature been as great at the commencement as at 
the finish, the ore would have fused and matted; but 
the volatile and combustible gases having been driven 
off at low red heat, there is not much danger of 
fusion on the hot hearth at a cherry-red heat. The 
loss of gold from volatilization with salt commences 
at 100° C. and increases until it reaches its maximum 
at 250° C. 

Below red heat the loss diminishes, but increases 
to a maximum above melting heat. 

Prof. Christy gives the following losses of gold in 
a stream of chlorine gas with different temperatures: 

At incipient redness the standard loss was 0.05 per 
cent in half an hour. 

At a low red heat it is o. 10 per cent. 

At a cherry-red heat it is 0.25 to 0,35 per cent. 

At incipient yellow it is 0.40 per cent. 

At melting heat it is o, 50 -f- per cent. 

These results show the proper regulation of tem- 
perature to be important in chloridizing roasting; also, 
BKthat the proper place for salt is at the end or hot 

C i 


hearth of the roast; furthermore, that at that end an 
over supply of salt is not beneficial, since the chloride 
of sodium with otlier impurities might produce fusion 
by making a flux. 

It has been ascertained that loss of gold may occur 
from volatilization when a high heat is maintained for 
a long time if salt be mixed with the ore. From 
the foregoing it may be surmised that increased tem- 
perature does not assist roasting with salt, and conse- 
quently time cannot be gained except at the expense 
of gold, and afterwards leaching. 

Time, again, as a factor in chloridizing roasting de- 
pends upon the amount of sulphur or other volatile 
impurities. While roasting, as stated, can be forced 
up to a certain limit by mechanical contrivances 
and automatic furnaces, "dead roasting" cannot mate- 
rially be hastened. 

The amount of impurities may be so small and so 
readily reduced, that mere contact with heat will 
allow reduction, but generally time and patience 
are required. 

In one instance we have ore oxidized from 30 to 
7 per cent of sulphur by falling slowly through the 
furnace; in another instance we find it requires 32 
hours to " roast dead " from a 30^ sulphur ore, and 
at times it may require even more than this. 

In chlorination so much depends upon the roastini 



that no specified time can be stated that will be 
applicable to every ore. By hastening the operation ! 
we run chances of ruining the roast by melting; and ' 
also loss of the metal we desire to save, when tel- 
lurides, arsenides, and zinc sulphides are volatilized. 
The Austin process of pyritic smelting, which is prac- 
tised under certain circumstances to utilize the heat 
of the burning suiphur and melt the metal to a matte, 
fully illustrates the heat which may be evolved from 
pyritic ores, and which in our case must be avoided. 
The whole process of chlorination depends upon the 
care taken to obtain a uniform and complete roast. 

The deductions we may make as far as regards 
pyritic ore roasting are: 

1. Sulphur can be removed in part by heat, more 
fully by a plentiful supply of air with heat, and prac- 
tically eliminated by salt and heat. 

2. Sulphates can be decomposed by air, heat, and 
chlorine, combined or separate; but sulphides must 
be converted into sulphates by heat with air, and 
finally with heat, air, and chlorine gas, in our case. 

3. Fusion or sintering prevents further desulphuri- 
zation or formation of sulphates, therefore oxidation 
or chloridizing roasting. 

4. Loss of gold is not apt to occur in oxidizing 
H roasting where care is used, while with salt added to 
^^the ore at the commencement instead of the end of 



the roast it is considerable, even when great care is 

Prof. Christy found by experiment that the loss in 
the latter instance was 308 times greater than in the 

5. Salt should be added at the end of the roast 
after sulphur has ceased to be evolved, and in propor- 
tions which have by experiment proved to be suffi- 

Loss of weight occurs when ore is roasted by the 
volatilization of volatile compounds. The roasted 
ore is consequently richer in precious metal per ton 
than raw ore. To make one ton of roasted ore 
from 33J percent sulphur ore will require 1.3 tons 
of raw ore. Salt will add a trifle to the weight of 
the ore, but the other impurities driven off will 
counterbalance that. 

If the raw ore assays $15 per ton in gold and no 
loss occurs, the roasted ore should assay one third 
more, or $20 per ton. 

The theory' of roasting is explained as follows: 

1. The conversion of sulphides into sulphates. 

2. By raising the temperature the sulphates are 
decomposed in the following order of the metal com- 

Iron, copper, silver, nickel, zinc, lead. 

Mr. A. Theis gives the following simple plan fori 



testing the degree of roast in the furnace: " A small 
portion of the ore from the furnace is boiled in water 
and stirred with a bright iron rod. The least stain of 
sulphur on the rod will show that roasting is not 

Second Test. — Ferricyanide of potassium will indi- 
cate the absence of any ferrous salt. A portion of 
the roasted ore is boiled, and if any ferrous salt be 
present in the ore a blue coloration will be given to 
the liquor on the addition of ferricyanide of potas- 
sium. This only indicates a dead roast as far as iron 
is concerned. 

Efficient roasting- furnaces must allow easy con- 
trol of the heat, abundant access of air to the hot 
ore, and rapid removal of the products of combustion. 
These specifications require large, flat hearths, that 
the ore may be spread out thin, otherwise small ore 
charges would be necessary; large throats leading to 
stacks; and small, shallow fireplaces, that the fire may 
be easily regulated. Should the draft not be suffi- 
cient to remove the products of combustion quickly, 
artificial draft must be resorted to, or the stack made 
higher and larger in the flue. This forced draft will 
require the construction of dust-chambers, and if 
much arsenic or other volatile substances are present 
they will be necessary under all circumstances, as the 
current of hot air will carry off the fumes and dust, 
and with them fine gold, either mechanically or chem- 

Full details of the various furnaces invented and 
discarded, with their good and bad points, is beyond 
the province of this work; we will therefore confin< 




our attention to those which are in common use and 
the causes which have led up to their adoption. 

Where one furnace wil! give entire satisfaction in 
one locality it will not in another, and the chloridiz- 
iiig roasting for the chlorination process requires 
much more careful work than the same roasting for 
the Russell process, or for the amalgamation of silver 
ores after roasting. Still, at times it is within the 
province of chlorination to use the mechanical fur- 
naces to great advantage where low percentages of 
base metals and sulphides are in the ore; but 
where they are above 8 per cent, "dead roasting" 
is a difficult matter, and we have no authentic 
accounts which will allow us to assert that for our 
purpose mechanical roasting above that limit can be 

There are two classes of furnaces to choose from — 
those favored by mechanical engineers, and those 
liked by metallurgists. 

At this date inventors realize that the sale of a 
furnace will not lead to success in their line; conse- 
quently they wish to test the ore to be roasted, when, 
if their furnace proves efficient, they will guarantee 
it to do the work at a certain cost per ton. 

Roasting sulphides commenced with pile-roasting 

the open air. This method oxidized a portion 

of the pile, smelted another portion, and answers 


"' I 


to-day where matte is wanted, but is not advisable I 
for chlorination. The assortment, the grading, the 
sledging, handling, and carting, and, finally, the re- 
roasting of fully one third the pile, made inventors in 
Wales look for some method of oxidizing roasting 
which would do better and cheaper work in less time. 
The result was the reverberatory furnace, which has 
been modified, enlarged, and improved in shape as the 
objects to be attained became better known. They ■ 
were first constructed as in our illustration, where the J 

charge was roasted and withdrawn into a cooling pit; 
from this construction they were lengthened to < 
long hearth; and, finally, steps were added to assist! 
in working the charges forward, as it became evidenti 
nothing could be gained by increased heat in the I 

The rabbling or stirridg next attracted attention. 
What is known as the Spence furnace is an English 
invention of Peter Spence. These have rakes 
attached to a rigid frame, which are operated by 
automatically reversing the engine. The adjustment 
is such that ore is admitted to the furnace at the 
same rate it is discharged, and falls from hearth to 
hearth as desired. The clogging and wear of the 
rakes was an objection, but this is said to be over- 
come by cooling the rake. 

The American modification of the Spence furnace 
is known as the O'Hara, In this furnace the rakes 
are moved forward by an endless chain. It is pro- 
vided with two hearths, and the rakes are attached to 
carriers which extend through slots in the side walls 
and which move the chain, thus being away from 
the heat and sulphurous acid of the burning and 
roasting ore. This furnace will roast 40 tons per day 
down to 7 per cent of sulphur. The wear and tear 
upon the mechanical parts is high in spite of the pre- 
cautions taken to obviate it. 

The Pearce Turret furnace has hollow arms moved 
by simple machinery situated in the open space 
within the annular bed. These arms are cooled by 
air, which, passing through them, is forced against 
the rakes and on the ore. 

The Spence furnace built with steps is continuous 



in its action, as many as five steps and hearths 
being used. 

Mr. Peters gives an account of the furnaces which 
he built at Butte, Montana, as 64 X 16 feet outside, 
with four hearths, each 14 X 15 feet wide in the 
clear. The ore is charged from a hopper upon the 
hearth farthest from the fire in 3600-lb. charges, 
and in that position will become a bright red in two 
hours. Each furnace calcines 11 tons ore in 24 hours, 
from 30 to below 4 per cent sulphur, and consumes 
2 cords pine wood, only the labor of two men being 
required. A similarly constructed furnace is used at 
the Treadwell mill in Alaska, where dead roasting is 

The Brown Horseshoe furnace is a somewhat lab 
invention, and does good work on low-sulphu; 

To obtain a " dead roast " from high-sulphur ores 
we are obliged to leave the mechanical furnaces, and 
either use them in preliminary roasting, followed by 
the use of the reverberatory for finishing roast, or else 
discard them for the reverberatory entirely. . 

The disadvantages in a measure overcome by th«!j 
mechanical rabbling of the Spence and other furnaces 
can be further overcome by the revolving furnaces of 
the Bruckner type, or the revolving pan-furnace with 
fixed rabbles, but in either case the dead roasting 
must be done in the reverberatory. 




The shaft furnaces, such as the Stetefelt, are fairly 
good for chlorination of silver ores, but will not answer 
for the gold chlorination process. 

Ores carrying a high percentage of arsenic, zinc, 
tellurium, bismuth, antimony, and a low percentage 
of sulphur can be sufficiently roasted in the mechani- 
cal furnaces at a low cost, but the advantages of these 
furnaces for a high percentage of sulphides in the ore 
have yet to be demonstrated. 

The old reverberatory, like the beehive coke oven, 
seems to hold its own against all comers as far as 
uniformity and product is concerned. 

The reverberatory furnace is so well known among 
professional men, the description would be omitted 
were it not the object of this book to reach the 
student and non-professional man not so well in- 

In our illustration, Fig. 1, //"represents the hopper 
through which ore is charged to the hearth O. On 
this hearth it is spread out in a thin uniform layer. 
The hopper is provided with a cover, which is closed 
as soon as the oven is charged. G is the fire-box 
provided with grate-bars, fire-doors, and ash-pit. 
. The fuel usually burned is wood, as it is free from 
sulphur and ash, which might in a measure reach the 
ore, and, furthermore, a wood fire is more readily con- 
trolled- The flame from the burning fuel is separated 





from the ore on the hearth by the bridge B. This 
bridge also raises the flame against the fire-brick 
arch, which reflects it down upon the ore. It is this 
reflected or turned back heat which gives this style of 
furnace its name. 

As the flame approaches the stack it becomes 
cooler, and for that reason the arch pitches towards 
the hearth gradually until it meets the throat, where 
after passing the ore it goes through a straight flue 
and up the chimney. The apertures DD are working- 


doors through which the ore is spread upon the 
hearth as well as stirred during roasting, E is the 
discharge-pit for the calcined ore. 

By reference to the figure it may be seen that con- 
siderable heat might be saved if the furnace was 
longer, or longer with steps, the under side of the 
throat of the first furnace being raised to answer as a 
fire-bridge for the second in the latter instance. 

With the same object in view return-flues are built 


underneath the hearth; again, one furnace is built 
above the other in such a way that the flame passes 
from the ftret furnace up and back over the hearth 
of the upper one and then up the stack. 

The latter style of furnace is termed a " double- 
hearth," and is worked as follows: The top is used for 
drying the ore, after which it is dropped to the first 
hearth, upon which it is allowed to remain twelve 
hours. This charge is then dropped to the lower 
hearth and a new charge placed in the upper. After 
remaining a sufficient time on the lower hearth to 
allow sulphur fumes to cease, salt is added and well 
stirred into the ore. The time required for this roast- 
ing is about twenty-four hours. 

The furnace has the advantage of utilizing space, of 
continuous roasting, of creating little flue-dust, and 
lessening fuel expenses. The size of such a furnace 
is i8 feet long, 15 feet high, and with low fire-brick 
domes or arches, cast-iron working-doors, and other 
appurtenances will cost approximately $1.50 per 
cubic foot. 

Step-furnaces are built as in our illustration, but 
one furnace is raised three to four feet above the 
hearth of. the other. The ore can be more readily 
kept separated and transferred from one hearth to 
the next in this furnace. The domes can be brought 
lower to the ore as well, where with one long con- 




tinued reverberatory this cannot so readily be accoiK- 
plished. These furnaces are about 60 feet Jong and 
15 feet wide, will roast 3 tons per day, and have a 
capacity of about g tons of raw ore. The charges are 
kept separate and the roasting is continuous. One 
hearth reverberatory furnace of the above dimensions 
will cost $2 per square foot of ground-space; step 
reverberatories will cost $2.50 per square foot of 
ground-space. ■ 

The working of such furnaces is illustrated as fol-J 

Charged at 8 a.m. 2500 lbs. raw concentrates, well 
dried and free from moisture. 

8.30 A.M. Sulphur commences to flame on the 
4th hearth. Fire good. 

10 A.M. Moved charge to 3d hearth; sulphur 
burning briskly; ore hot and red. Fire almost 
without fuel. Charged the 4th hearth. 

2.30 P.M. Moved ore to 2d hearth, lai^e quanti- 
ties of sulphur fumes being given off. Fire- 
place dark; ore red. Moved ore from the 4th 
to the 3d hearth; sulphur burning freely. 
Charged the 4th hearth. 

3,30 P.M. Combustion of sulphur on 2d hearth; 
decreasing ore swelling slightly. Fireplace 
dark. Ore on 3d hearth giving off Isrge 


quantities of sulphur; ore dark red. Ore t 
the 4th hearth coinmencing to burn. 
4.30 P.M. Combustion of sulphur ceased on 2d 
hearth; added 3 per cent salt and mixed well. 
Added fuel to the fire. Ore on the 3d hearth 
giving oR large quantities of sulphur fumes; 
ore on 4th hearth burning briskly. I 

5 P.M. Charges passed from 2d to 1st hearth, ' 

3d to 2d, 4th to 3d, and new charge placed on 
the 4th hearth. Fire hot, but not much 
chlorine fumes given off. 
5.30 P.M. Chlorine fumes ceased. Fire red-hot. 
Ore Swelling slightly on 2d hearth; sulphur 
burning briskly on 3d hearth; sulphur just 
commencing to flame on the 4th hearth. 

6 P.M. Charge drawn from the ist hearth into 

the pit. Ore moved from 2d to ist hearth, 
from 3d to 2d, from 4th to 3d, and new charge 
added to the 4th, 
In this continuous manner roasting is carried on 
day in and out. 

The roasted ore is not immediately removed from 
the pit; it is left there some time, to allow chlorine 
fumes to pass off. 

It is then taken to the cooling floor and allowed to 
become cold, when it is dampened and elevated to the 
chlorinator floor. 


Wetting down roasted ore when red-hot is likely 
to cause " balHng, " in which condition it is not in 
proper shape for chlorinating, it being difificult for 
chlorine to penetrate the balls and extract the gold. ■ 

In this connection we may also note that raw con-J 
ccntrates should be kept moistened until ready for 
use, when they are dried quickly; otherwise they will 
be likely to form lumps, which are difficult to roast 
thoroughly, and thus again a loss in leaching from 
imperfect oxidation. 

The revolving-hearth furnace is an iron pan which 
carries the ore to be roasted. It is geared to revolve 
horizontally, and has fixed rabbles which stir up the 
ore as it comes in contact with them, thus exposing 
new faces to the heat. These furnaces do excellent 
work, but, as before noted, are not able to do " dead 
roasting" without the aid of a small reverberatory 
attached. Prof, Phillips* gives the dimensions of 
one used by Mr. Theis, which roasted 3 tons of con- 
centrates in 36 hours, desulphurizing pyrites from 32 
to 0.25 per cent. 

Diameter of the hearth or pan 12 ft. 


Height of dome from centre of pan 30 i: 

Furnace-wall thickness 14 i: 

I, Trans. A, I. M, E. 


Fire-Lox 6 ft. j 

Grate-surface, 2 X 3 6 ft. 

Fire-bridge height 2 ft. 

Throat length, 4 ft. ; height 16 in., area 5 ft. 4 in. 
Working-doors (one each side) 8 X 16 in. 

Reverberatory attached : 

Length 14 ft. 

Width inside ^ f t. I 

Spring of arch , 2 ft. | 

Working-doors (one each side) 8 X 16 in. 

Dust-chamber 4 X 3 X 20 ft. 

Spring of dust-chamber arch 18 in. 

The cost given for roasting by this furnace one ton 
of concentrates: 

J cord wood, at $1.40 $0.70 

12 hours' labor, at 9 cts 1.08 

Motive power 0.25 

Cost per ton of concentrates $2.03 

As it requires 1.3 tons of such concentrates to 
make one ton of roasted ore, the cost of roasting one 
ton of ore would be $2.64. 

Of the revolving-cylinder furnaces we must say the 
same as for the other mechanical furnaces. 

The Bruckner furnace as originally designed was 


intermittent in discharge, and could roast but one 
charge at a time. It was a wrought-iron cylinder, 
lined with 4-in. curved fire-brick, usually 18 to 22 feet 
long and 6 to 8.5 feet in diameter. 

The cylinder had two orifices, one at each end; a 
manhole for the receipt of the ore, and its discharge 
after roasting. The motion was around a horizontal 




axis, but as improved the cylinder turns on rollers 
geared to the motive-power shaft. 

The two contracted orifices, one at each end, are 
for the fire and escape of the products of combustion. 
In Fig. 3 an improved Bruckner roasting-cylinder is 
shown, one end connected with a movable furnace, 
the other with the dust-chamber D. The movable 


furnace F is connected with the cylinder until the 
charge commences to blaze, when it is removed, and 
only reattached to complete the roast. // represents 
the hopper through which the ore is charged. 

These furnaces are better adapted to tlie roasting 
of silver ores, in which case they will roast 9 tons 
concentrates inserted in one charge from 30 to 5 per 
cent sulphur in 24 hours. 

In some cases the cylinder is made with four man- 
holes or discharging-doors, and lined with tire-brick 
at the throats and red brick inside the cylinder. 

The 8.5 X 18.5 feet cylinder has a capacity of 9 
tons, and weighs 4.5,000 lbs. 

The throat-linings require 100 fire-brick. 

Fire-box, 500 fire-brick and 4135 red bricks. 

The body of cylinder, 4300 bricks. 

If movable fire-box is used, 2S00 more fire-brick 
are required. 

These furnaces when used for chloridizing roasting 
and chlorination, possess the advantage of allowing 
desulphurization of base ores before salt is added, 
thus obviating one difficulty of mixing the salt with 
the ore at the commencement of the roast. The 
Eriickner furnace has some of the advantages of the 
reverberatory, as well as its disadvantages, increased. 
The percentage of sulphur may be decreased, also 
the heat readily controlled. The charge may be 


retained in the furnace as long as desired, and tested 
for the degree of roast required. 

It was the intention of Mr. Brflckner to make the 
furnace automatic and continuous by placing two 
furnaces in a line, but stepped one below the other 
and connected by a feed-pipe. The fire was to be 
made at the lower cylinder and circulate through 
both, thus effecting a saving in fuel. The results for 
comparison between Bruckner and reverberatory fur- 
naces are not in favor of the Brilckner for dead 
roasting for a high-sulphur ore. Where low-sulphur 
ores are roasted, the advantage must be with the 

The disadvantages of the furnace are: 

Care must be taken not to let the heat get " too 
light a yellow," as the charge will ball. 

The charge has to be heated to a " dark yellow," 
and become sticky to avoid flue-dust, in which case 
it balls if the ore be fed dry. If the charge is wet 
the ores have to be heated to a dark red, which is the 
condition for flue-dust to form. The damper must 
be closed and a hot fire kept up until the ore is a 
dark yellow, when it becomes sticky and liable to 
ball. This balling is a great drawback to chlorinating, 
as the ore thus roasted must be recrushed before 
being placed in the Icaching-barrels; but in such 
masses it cannot be properly " roasted dead." The 



makers say it is possible to roast ores to as low a per- 
centage of sulphur in the BriJckner furnace as in a 
hand reverberatory furnace if the operators are ex- 

For desulphurizing where dead roasting is not 
required these furnaces are well liked, one firm using 
168 of them, roasting from 40 to 7 per cent sulphur 
with 167 lbs. of coal to the ton of ore roasted. There 
is another advantage which will apply to almost any 
furnace — a further decrease in the cost of roasting by 
the use of fuel-gas. The simplicity of modern fuel- 
gas producers allows almost any fuel to be converted 
into gas at a moderate cost, and the gas fixed or 
purified to avoid any deleterious mixtures with the 
ore. The Mond Gas Producer will produce 60,000 
cubic feet of gas from one ton of inferior coal, coke, 
or peat; and equally good results may be obtained 
from our modern producers, such as Loomis or Tay- 
lor's, although they do not claim as much. 

The Bruckner furnace has been improved in various 
details, among which is Clark's oxidizing and desul- 
phurizing apparatus, which brings the air in contact 
with the ore by means of a pipe running through the 
furnace. This pipe is water-jacketed to keep it cool, 
while air is forced through it and from apertures in it 
to the cylinder. This principle of adding more air is 
correct in every detail, as naturally what air is admitted 


to the throat rises to the top of the cylinder without 
coming in contact with the ore, and so out the stack. 
The air forced in, however, through the pipe would 
come in contact with the ore and drive the sulphur 
fumes from the burning ore to the top of the cylinder 
and allow quicker oxidation. 

These furnaces are revolved at the rate of lOO feet 
per minute, and should not be above that. If the 
charge is working properly, it goes half-way up the 
sides of the furnace and slides back; if above this 
point it is too hot, if below this too cold. 

The cost of a Bruckner furnace will depend uponJ 
freight rates from some manufacturing point. 

A 20 >^ 8 furnace will weigh 45,000 lbs. It is 
composed of iron work as follows: 20 X 8 ft. iron 
cylinder, one movable fire-box, one 60 ft, X 30 i 
iron stack, one conveyor, one hopper and driving- 1 
gear, driving-shaft, countershaft, pulleys, pillow- • 
blocks, etc., complete. 

There are needed 3400 fire-brick, lo.ocx) red brick, 
8 bbls. fire-clay, lime, and cement. 

The labor of one machinist, two bricklayers, and I 
three helpers, lO days. 

The building for the furnace will be 30 X 2C ft. 

The cost in dollars and cents will approximately bflS 


Cylinder and appurtenances $2,500.00 

Fire, red bricks and lime, 335-00 

Labor 2 lO.OO 

Building 30 X 20 at $1.50 per sq. ft. 

of ground surface 900.00 

Total $3,945.00 

To which must be added the freight. 

The Howell or Oxland furnace is a modification of 
the Bruckner. The Howell-White differs but little 
from the Howell, and what is termed the improved 
White is a trifle different yet. They are all rotating 
cylinders, provided, as in the Howeil-White, with 
cast-iron shelves, which raise the ore and let it drop 
back as it rotates. They are made 30 feet long and 
5 feet in diameter, lined entirely throughout with 4^- 
inch curved fire-brick. The Howell-White has but 
one end lined with these bricks, while the metal on 
the smaller portion is exposed. This smaller portion 
has cast-iron spirally arranged shelves, which showers 
the ore through the flames as it turns. 

The roasting capacity of a 60 in. X 27 ft. furnace 
is stated to be from 30 to 45 tons per day. The 
amount of brick required for lining furnaces and 20 
feet of dust-chamber is 28,000 red brick and 2700 
fire-brick; fire-clay is also required. 

The Improved White roasting- furnace differs only 



in being a long cast-iron revolving cylinder, lined? 
throughout with fire-brick. These fire-brick are J 
curved to the inner circumference of the cylinder, and I 
are 4^ inches thick. The shelves are made by insert- 1 
ing key-brick 9 inches thick in rows, which make a j 
projection of 4^ inches. These shelves run nearly 
the entire length of the cylinder. The greater the 

number of shelves the more dust is made, and for this 
reason the shelves have been reduced from 8 to 6. 

A furnace 60 inches in diameter and 30 feet long 
will require 28,000 red brick, gooo fire-brick, and 
3 bbls. of fire-clay. The capacity is from 30 to 45 
tons per day. The weight of these cylinders is 
about 28,000 lbs., including bearing-wheels, chairs, 
sole-plates, gearing, and bolts, exclusive of brick 
and other paraphernalia. 

These cylinders are inclined toward the fire end, 
and fed at the upper end by a screw feeder situated 
as shown in the figure. They are continuous in 



operation, discharging the product regularly into a 
pit at the lower end, from which the roasted pulp is 
withdrawn as required. 

Working the ore towards the fire is the true theory 
of perfect roasting, while the expenditure of power — 7 
to 13 H.p. — is not unreasonable for the size of furnace. 

The shelves, as mentioned, create considerable 
dust, and this requires mechanical drafting to remove 
with the products of combustion. 

This drafting creates another difficulty: dust leaves 
the cylinder, as does fine ore, before it is thoroughly 
chloridized. We have noticed also that if salt is 
used the chances for loss of gold are greatly ad- 
vanced, when the salt is mixed with the ore at the 
commencement of the roast. 

To roast this flue-dust Mr. Hoffman added a fur- 
nace at the dust-chamber end, which necessitated two 
fires. This did not entirely obviate the difficulty; 
and in some instances with automatic charging one 
third of the ore went into the dust-chamber instead of 
through the cylinder, and not being sufficiently chlo- 
ridized had to be reroasted with salt. To charge out 
of line of draft one or two patents were taken out, 
and in another instance a collar was inserted, which 
formed a sort of chamber which possibly stopped the 
draft and some of the dust. 

Mr. Rumsey claimed for this latter patent that the 


chamber formed at the head of the cylinder held the 
dust until roasted, after which it would fall to the 
bottom of the cylinder and move with the heavier 
ore down the cylinder and out with the roasted pulp. 

Tlie HoiTman roasting-furnace is a revolving cyl- 
inder of the Bruckner type, with a fire-place at each 
end, also a fiue. 

The flues are between the fire-places and cj'linder, 
descending to dust-chambers which are connected with 
the main flue. By means of dampers the current of 
air can be reversed to go in either direction, and thus 
expose the ore charge to a uniform temperature. 

The furnace is suitable for ores which require a 
very high or low roasting temperature. 

The Brown Horseshoe Furnace is constructed in 
the shape of a circle, with one fifth of the circle left 
out. The cross-section gives an arch the same as the 
common reverberatory. The stirrers are mechanical, 
and move on carriages running on tracks in chamben^ 
on each side of the furnace. The ore is charged 
and discharged automatically, always working against 
the hot furnace. The fumes may afTect the carrier3-| 
and moving mechanism, with all the protection 
offered. The stirrers make the round of the furnace, 
and then stop to cool off in the one-fifth open space; 
they work automatically. The stirrers do not, it \gy 
claimed, by this cooling process become overheated. 



The points of superiority are claimed for this fur- 
nace as follows: 

1. It is simple in construction, requiring no more 
brick or iron work than the ordinary reverberatory 
furnace of the same length of hearth. 

2. It is 50 per cent less in cost than any other 
mechanically stirred furnace of the same capacity. j 

3. The operating mechanism is most easy to man- 
age, and least liable to get out of order, 

4. The carriages moving the rakes, standing half 
the time in the open air, are kept thoroughly cooled, 
and are at all times perfectly accessible. 

5. Less manual labor is required, one man on a 
shift taking care of the machinery and fires for a fur- 
nace of 40 to 60 tons daily capacity. 

6. The hearth being on one plane, no dust is raised 
by the falling ore, and no loss of heat, as is the case 
with furnaces having upper and lower hearths. 

7. The feed is automatic, introducing any required 
quantity of ore with the passage of each rake, the 
amount being governed by a counterpoised lever 
which weighs each charge. 

8. The machinery is perfectly noiseless in opera- 

9. All the journals that are exposed in any manner 
to the heat are fitted with ball- or roller-bearings 
requiring no lubrication. 


It is claimed to give a " dead roast " on high- 
sulphur ores. The author has had no opportunity to 
thoroughly Inspect the working of this furnace, and 
no data but the maker's to go by. The reports re- 
ceived, however, are such as to warrant the assertion 
that this furnace is a great improvement in mechani- 
cal roasting- furnaces, and worthy further investigation, 

Mr, R. P. Rothwell gives an account of one of 
the Howell-White furnaces used by him at Deloro, 
Canada, in roasting ores carrying 40 per cent arsenic. 
He was able to obtain 93 per cent of the gold by its 
use. The arsenic fumes being very dense, flues as 
well as dust-chambers were necessary. The forced 
draft was obtained by a Guibal fan. 

The dryer was an inclined revolving cylinder 48 
inches diameter at the mouth and 36 inches diameter 
at the throat, with a conical addition at the throat 
making its total length 22 feet. Fire passed througji 
this cylinder, from which the ore dropped in a contin- 
uous manner into a boot, and was raised by elevator 
buckets into No. i roasting cylinder. 

This was a revolving cylinder 30 X 5 feet, was sim- 
ilar in lining and shelves to the Howell described 
above. From this the ore ran direct into a second 
roasting cylinder 20 X 4 feet, lined as above, and in 
which the roasting was completed. The cost of 
ing these ores is given as 60 cents per ton, the fui 




f roast* :^^J 


roasting lo tons in 24 hours. This ore is more readily 
roasted than simple sulphurets would be. 

The obstacles encountered were flue-dust, loss of 
fine gold carried away by the dust, aided by the 
arsenic fumes and volatilization. 

Having prepared the ore for roasting, and by 
roasting for leaching, we come to that stage oi ihc 
process where the outlay from the foregoing is to be 
recovered with interest, in the first chapter we dealt 
somewhat at length upon this subject, but additional 
information of the action of chlorine and its, to us, 
most interesting compound of gold will not be out of 

Auric chloride, the most important compound of 
gold, is a red crystalline mass when evaporated to 
dryness, soluble in water. When combined with 
other metal chlorides, it forms double salts, termed 
cbloro-au rates, the general formula of which is MCI, 
AijCI., where M represents an atom of a monad metal. 
These compounds are mostly yellow in crystals, but 
red when deprived of the water of crystallization. 
It seems to make no difference to chlorine whether 
the gold is cold or warm, provided no other impurities 
are present with which chlorine unites. 



If auric chloride (AuCI,) be heated above 130° C. 
subchloride of gold is formed ; and by warming AuCl, , 
or gold sponge, in AuCl, a double chloride, AuCl, , 
AuCl, , is formed. 

Pratt says AuCl, heated in chlorine gas forms a ■ 
higher gold chloride. 

Chlorine gas for chlorination is usually generated 
from solutions of bleaching-powder * by sulphuric 
acid. We may consider the bleaching-powder to 
have the formula CaO ■\- CI, , and then to have had its 
CI displaced by the air, carbonic acid, or oxygen, and 
become CaOCI,. The reaction then would be: 

Au + CaOC!, + H,SO. = AuCl. + CaSO, + H.O. 

This may not be the direct action — that point seems 
to be in doubt; but the ultimate reaction is as given, 
a gold chloride being formed when nascent chlorine is 
liberated by sulphuric acid in the presence of gold, 

The chlorination process is based upon this reaction. 

The Plattner process of chlorination is practised as 
follows : 

The ore is crushed, concentrated, roasted with salt. 

* Hleaching-powder is composed of CaCl, + CaCl.O, , calcJum 

Roscoe (VI., p, 176) considers hypochlorite to be the Important 
factor. The result for our purpose is, however, ultlmaiel) the 


and sifted into large wooden vats, which are slightly 
raised at one side to insure drainage. 

There is a filter-bed (described in Chapter VI) in 
the bottom of these tanks, through which the liquor 
containing the auric chloride is drained, and collected 
for precipitation (see Chapter VII, p. 8l). 

The vats are of a size to suit the operator — say 9 
feet in diameter and 3 feet deep, or 12 feet in diam- 
eter and 4 feet deep. The depth, however, shouH, 
not exceed 4 feet, unless mechanical contrivances arc 
employed to remove the tailings from the vats after 
leaching. These vats should be lead-lined, although 
this is not absolutely necessary, but will prevent 
leakages and possibly loss of gold chloride in solu- 

This process requires about four days, and on that 
account four leaching-vats, to allow of one being 
cleaned and charged daily. The charge for a 9 X 3 
ft. tank is 4 tons, and for a 12 X 4 ft. tank 7 tons, of 
roasted concentrates. 

In order to sift the concentrates into the tank so as 
to lie loosely and avoid packing, they are slightly 
dampened, with enough water to form a ball in the 
hand when squeezed, which will crumble, however, 
when the hand is opened and pressure removed. This 
looseness allows the chlorine gas to permeate the ore, 
which it could not so readily do were it packed in the 



tank. A coarse screen over the tank is used for this 
sifting, and the tanks nearly filled with ore, but space 
enough left to assure the ore being covered with 
water after gassing. The gas is generated in an 
apparatus (usually two generators), which causes it 
to flow into the bottom of the tank at two opposite 
points and work upwards through the ore. This gas- 
sing continues until ammonia held over the ore gives 
off the dense fmnes of ammonium chloride; the tanks 
are then covered with lids, and the lids luted with 
clay to prevent any escape of gas. This operation 
requires about three hours. 

The tank being charged with chlorine gas is left 
standing with the gas in contact with ore two days. 
The gas is not forced into these tanks by pressure, 
but continues to generate and go into them for a time 
after the covers are placed on them. The amount 
of gas required is fairly well known for one class of 
ores, as is the amount of chemicals, so that the gener- 
ators are charged accordingly to supply that quantity. 

On the third day the ore is leached by filling the 
tanks with water, which immediately dissolves the 
gold chloride and holds it in suspension. 

The gold chloride is now fixed, and can only be pre- 
cipitated by some metal salt, as metallic gold. This 
solution is now filtered off by removing the plugs or 
opening lead spigots at the bottom of the vat. Wash- 


water is added until upon testing no chlorine appears 
to be present, when we may consider the leaching to 
have been completed. Water is added in sufficient 
quantities to keep the tank full during this process. 
This leaching process requires from four to five hours. 

G. W. Small * gives an account of tank chlorination 
at the Plymouth Mining Co. 's chlorination-works in 
California, where the ore was passed through a 35- 
mesh screen, 1205 holes to the square inch, which 
allowed quick leaching and a recovery of 95 per cent 
of the gold. The liquor from the tank is run or 
pumped into settling-tanks, where sulphuric acid is 
added, to hold in suspension any impurities which the 
excess of water has dissolved from the ore, and also 
to allow mechanical impurities in suspension to settle 
in these tanks rather than in the precipitation-tanks. 
After settling, the liquor is drawn off into precipita- 
tion-tanks, where the gold is thrown down as a 
brownish precipitate by ferrous sulphate, which proc- 
ess will be explained in Chapter VII. 

If lime or talc is present in the concentrates, the 
ore in roasting may have its lime converted into sul- 
phide of lime. This sulphide must be entirely 
decomposed, or the leaching in the vat or barrel will 
prove unsatisfactory. 

" Trans. A. I. M. E., vol. XV. p. 307. 



The chlorine will be converted into calcium chloride, 
and, furthermore, hydrogen sulphide will be evolved, 
which will precipitate the gold from the auric chloride 
solution as fast as formed until the excess of chlorine 
gas ceases. This will be lost with the tailings, 
unless reroasted and retreated. 

" To use the Plattner process on lime ores, no 
calcium sulphide should be present in the material 
when it enters the leaching-vat. " 

Whenever the lime is in the shape of chloride of 
calcium, leaching can occur without loss ; but no roast- 
ing test will determine the presence of calcium sul- 

If carbonates be present in the ores, the hypo- 
chlorite of calcium in the bleaching-powder will be 
decomposed, and consequently the hypochlorous acid 
will remain inert. 

The Mears process had for its object a saving in 
time over the Plattner process. It is so similar in 
details with the Theis process that the two can be 
described together. The chlorine gas was generated 
for the Mears process outside the chlorinating-barrel, 
while in the Theis process it is generated inside the 
barrel. The latter process has entirely excluded the 
former, as far as barrel chlorination is concerned, on 
account of its simplicity and its removal of the 
objectionable features of the former. 



The chlorinator, Fig, 5, was with the Mears process 
a cast or sheet iron cyhnder capable of withstanding a 
pressure of 60 lbs. per square inch. This cylinder was 
lined with sheet lead weighing 10 lbs. to the square 

Fig. S. 

foot. It was fitted with cast-iron cylinder heads, ' 
which were securely bolted. It revolved upon a 
hollow trunnion, through which the gas was forced into 
the interior of the cylinder by means of a pressure- 
pump. This trunnion was arranged to admit at one 
end an iron lead-lined gas-pipe, termed a " goose- 
neck," one end being in the trunnion, the other out- 
side, upon which was a pressure-gauge to record the 


pressure inside the cylinder. The barrel was charged 
with roasted ore and chemicals, then rotated from 15 
to 20 times per minute. 

The Newberry- Vau tin process used compressed ait 
as well as the pressure generated by the chlorine gas. 
The air was to be compressed in wooden barrels to lOO 
lbs. per square inch, and that with the gas pressure 
was to permeate the rock. It had to permeate the 
rock or burst the barrel — we think the latter, as the 
process has come down to generating the pressure to 
20 lbs. in the barrel, and this pressure is proved to 
be necessary on account of the preliminary treatment 
of the ore. 

Mr. Theis ascertained that pressure was merely an 
accompaniment to barrel chlorination, and might be 
as readily obtained inside the barrel as out, the main 
object to be attained being the liberation of chlorine 
in the presence of gold, and under such conditions as 
would mechanically compel the gas to attack the gold 
in the least possible time. 

He therefore discarded the generator, gas-storage 
tank, and pressure-pump, and employed chloride of 
lime for the chlorine gas and sulphuric acid to lib- 
erate it, charging these chemicals in suitable propor- 
tions directly into the cylinder. 

This enabled him to do away with the hollow 
trunnion, and substitute solid shaft trunnions securely 


bolted to the heads and provided with tight and 
loose pulleys. The cylinder for a one-ton chlorinat- 
ing charge was made 42 inches diameter and 5 feet 
long. The " goose-neck," which was continually 
leaking, was next discarded, and in its place was sub- 
stituted a lead valve, by which the gas in the 
cylinder was tested to better advantage, thus obtain- 
ing more uniform extraction. 

The generation of gas in the cylinder is tested from 
time to time. The pressure-gauge might show con- 
siderable pressure in the cylinder, but there was no 
means by which it could be determined whether that 
pressure was chlorine gas or some other gas. In case 
it was the latter, and the gas shut off from the gen- 
erator, the extraction was poor; but by means of the 
lead cock chlorine is readily detected, and if free 
chlorine is not found present on testing, a time suit- 
able having elapsed, more lime and acid are added. 
It can be seen that an appliance which allows the 
gases in the cylinder to be tested, rather than by an 
uncertain pressure-gauge, is of immense importance. 

The illustration given, Fig. 5, is a one-ton chlori^J 
nating barrel of the Theis pattern. The cylinder 
may be cast or wrought iron with flanged ends. The 
heads are cast iron, with solid cast trunnions to rotate 
in suitable boxes. These heads are bolted to 1 
cylinder, and made perfectly air-tight. 

!er ■ 

..,te ^^ 
to th«^H 


The cocks for testing are shown on each side of the 
manhole H at C, C. 

The illustration gives the barrel with a geared 
flange at one end, and driven by a small wheel con- 
necting with the pulley-wheel; these barrels, however, 
may have the trunnion extended, and upon it loose 
and tight pulley-wheels for motive-power attach- 


Fig. 5a. Chforinating Barrell. Fig. 9b. 

ments. They may also be turned directly by belts 
passing around the barrels. With barrels larger than 
three tons capacity it is advisable to build them of 
wrought iron or steel boiler-plate, capable of standing 
150 lbs. pressure to the square inch. They should 
also rotate on tires bolted to them, as shown in the 
BrQckner furnace and Figs. 5« and b, these tires re- 
ceiving their revolving motion from the rollers upon 


which they rest. The rollers are keyed to shafts and 
connected by gears to motive-power shafts. 

A five-ton barrel, 6o inches in diameter and 9 feet 
long, could receive six charges in 24 hours, and is 
therefore capable of chlorinating 30 tons of roasted 
ore or concentrates per day. 

This size requires no more attention than a one-ton 
chlorinator, and is consequently less expensive to 
work. There is no specified limit to the length of 
these chlorinators : they can be made up to 20 feet, and 
chlorinate 20 tons at a charge. Their cost in such 
instances would not be as much as 4 five-ton chlori- 
nators, while their capacity would be 120 tons per day. 
With such large-sized chlorinators, from five tons up- 
wards, their ends should taper as do barrels — first, to 
allow the liquor to drain from the centre of the barrel 
or larger diameter, and, second, to allow of smaller 
heads which can be handled more readily, and which 
if subjected to high pressure need not be reinforced 
by braces. 

Fig. 5(7 gives an outline of such a barrel, with heads 
made of f-inch boiler-plate. The bolts which fasten 
the heads are to be countersunk inside. 

The shell is f-inch boiler-plate, 10 feet long, 60 
inches inside diameter at the centre, and 50 inches 
inside diameter at the ends. The object of bolting 
the cylinder-heads is to allow of quicker repairs and 


Examination of the lead lining, also to change the 
filter-bed with more facility. The lead lining is 
bolted to the shell by rows of flat-headed bolts or 
lead rivets spaced about iS or 20 inches apart. The 
sheet lead is dressed back against the iron shell with 
lead hammers or wooden mallets. There are two 
manholes instead of one, as in Fig. 5; size, 10 X 12 
inches. The Colorado Iron Works, the E. P, AlHs 
Co., and Fraser & Chalmers make a specialty of 
chlorinating plants; full particulars for these barrels 
can be obtained from them, together with their cost. 
The transverse joints should be single-riveted, the 
longitudinal double-riveted, since the cylinder may 
be called upon to withstand 60 to So lbs. pressure. 

The speed per minute for such barrels should not 
be over 100 feet. 

The method of charging these barrels is as follows; 

The barrel is first partially filled with water; the 
proper amount of chloride of lime is added ; on top of 
this the roasted ore is placed, and finally the proper 
amount of sulphuric acid. The manhole covers are 
then put on and screwed down tight, after which the 
barrel is set in motion. The water first put in the 
barrel is tor the purpose of making an easy-flowing 
pulp. The lime is added next, that it may more 
intimately mix with the ore, which latter will work 
through it. The sulphuric acid is added last, so that 


little gas may be generated before the covers 
and the barrel set in motion, and also as a precaution 
of safety. About one fifth more acid is added by 
weight than chloride of lime, the object being to 
convert all the lime possible into calcium sulphate, to 
remain on the filter as well as to set free all the chlo- 
rine gas from the chloride of lime. When lime passes 
the filter-boxes a bulky precipitate is produced in the 
settling-tanks, or if it passes the latter the precipita' 
tion-boxes; an excess of acid in the chlorinator will 
avoid this. 

Mr. Theis advocated and practised the division of 
the chemical charge. 

He first charged one half the amount of the lime. 
and acid into the ore and water mixture, then closed 
the chlorinator and rotated it three or four hours, 
after which the remaining half of the chemicals were 
added, and the chlorinator rotated two or three hours 
longer. By this method a possible saving of chemi- 
cals may occur, for if the ore were not properly 
roasted there would be free chlorine in the cylinder, 
but if properly roasted very little will be free. The 
time required for this process is from four to eight 
hours, between five and six hours being the average. 

The presence of free chlorine is detected by the 
means of the lead cock mentioned, and the cylinder 
rotated at least one hour after its detection to insui 




proper absorption of the gas by the water and metal. 
The ore is then discharged upon a shallow filter-bed 
below the barrel, or the cocks opened, when filtering 
is to take place from pressure applied inside the 

Aqua ammonia may be used as a test for free chlo- 
rine, as stated in the Plattner process. I 

The cause for the presence of gas being in the gen- 
erator, other than chlorine, or the cause why chlorine 
gas is not properly absorbed, may be traced almost 
entirely to improper roasting. If copper be present 
more bleaching-powder and acid are needed, and 
again the recovery may be so low that the whole 
charge must be dried and reroasted. Suppose, for 
example, we have roasted ore which we know assays 
$So per ton, and from which we generally recover 95 
per cent or $76, but from improper roasting we are 
only able to extract 80 per cent or $64. It will pay 
to reroast this charge and rechlorinate if we can 
recover 95 per cent, or $15.20 of the $16 present in 
the tailings; but the cost of chlorination was but 
$3.50 in the first place, and by double work it has 
mounted to $7. 

With proper care in roasting the percentage of 
recovery by barrel chlorination will be between 90 
and 98 per cent as the extremes and 94 as the aver- 
age extraction. 


Mr. Rothwell, one of the first to employ the Mears 
process, states that with a good roast 40 lbs. per 
square inch was given in the cylinder, but with a poor 
roast but 25 lbs. per square inch was recorded on the 
pressure-gauge in a certain time. This may be ex- 
plained in the first instance by the gold forming 
chloride and leaving an excess of gas, in the second 
by other chlorides being formed besides gold. 



The chloride of gold having formed in the chlori- 
nator, water is added to make a liquid pulp. The 
barrel is then revolved a few times to ivash out the 
chloride from the ore, and the pulp dumped direct 
upon the filter-bed. The barrel is now washed by 
water and a few more revolutions given it, this wash- 
water in turn is added to the filter-bed, the barrel is 
now ready for another charge. This practice may 
vary somewhat: the liquor may be decanted from 
the barrel direct into the filtering-tanks, wash-water 
added, and the ore and water run onto the beds; or 
the filtering may take place from the barrel itself, 
if provided with an asbestos or sand filter, in which 
latter instance pressure may be applied to hasten the 

Sand-filters are constructed as follows: For a one*, 
ton charge they are lead-lined boxes 6 feet wide, 8 
feet long, and 18 inches deep; for five-ton barrels 
they are S feet wide, 15 feet long, and 3 feet deep. 



The bottom is covered with clay or other substance 
impervious to water and not acted upon by action of 
acid and chlorine, such as perforated glazed tile. 
The bottom has a fall of about one inch in 8 feet. 
Upon the floor clean gravel-stones \ to i inch in' 
diameter are placed in a layer about 2 inches thick. 
Another layer of finer gravel-stones is placed over 
this about i inch thick, and upon this finer gravel 
about I inch thick, and lastly fine clean quartz sand, 
making a filter about 5 or 6 inches thick. To pre- 
vent the filter from getting uneven surfaces, strips of 
board \\ to 2 inches wide are laid about 10 inches 
apart on its surface. This filter is then flooded from 
below upwards until the water stands over the sur- 
face. The pulp from the chlorinator when discharged 
cushions on the water and slats, preventing the sur-i 
face from becoming uneven, also the filter from pack-' 
ing, and allows the pulp to flow evenly over the face 
of the filter-bed. The corks or rather plugs from the 
lower end of the filter-bed are now removed, and the 
liquor allowed to flow into the settling-tank. The 
filtering requires three or four hours, and is followed 
by a wash-water of from 150 to 300 gallons per ton of 
ore, or until no reaction is given, when the filtered 
water is tested with ferrous sulphate (FeSOJ. 

The reaction, if trichloride of gold is present, would 
present a reddish-brown precipitate of very fine 


brown gold, which reaction may be expressed as 
follows;* I 

2AuCl. + 6FeS0, = 2Au -[- Fe,Cl. + 2(Fe,0„ 3SO,). 

The filtrate should be quite clear, and the filtering 
accomplished as speedily as possible. So long as the 
solution shows the presence of free chlorine, when 
the last wash-water is leaving the filter, the ore has 
been thoroughly leached. f 

For each barrel there are four filter-boxes, so that 
at least one will be ready for use. When these 
filter-boxes are deep or have been used some time the 
rate of drainage is not satisfactory. Instead of drain- 
ing at the rate of three or four inches per hour, the 
drainage is not more than one inch or less per hour. 
Mr. E, G. Spilsbury advocated decanting the first 
water and the barrel wash, and only dumping the 
last wash and ore on the filter. Prof. Phillips does 
not approve of this method, and considers time lost 
rather than gained by so doing. 

Mr. R. P. Rothwell was one of the first to wash 

•See Chapt 


+ Chlorine v 

atcr decor 

nposes io 




g free 

Iodine when n 

ot in exce 

s. A di 


solution of m 



mixed with starch paste 



n the additi 

n of a tittle 

chlorine wate 

a blue tin 


h becomes c 



upon the addi 

ion of mor 

e chlorine 



The presenc 

e of chlori 

e is also 


ated if a while prec 


is formed by 

few drops 

of silver 

ate, AgNO.. 



the ore in the barrel and decant the liquor; the ore 
when thoroughly washed in the barrel was removed 
to the dump by a stream of water, not going into the 
filter. This system required much time for washing. 

The next step was to dump into a filter-box and 
wash under pressure; but this was objectionable be- 
cause of channels being formed in the filter-bed. 
through which the wash-water passed instead of uni- 
formly percolating through all the ore, making the 
washing very irregular. 

Mr. J. E. Rothwell turned his attention to wash- 
ing and filtering in the barrel under pressure. For 
this purpose he had drainage-holes made in the barrel 
on one side and on the other holes for connection 
with pressure-pump. At first he employed an as- 
bestos-cloth filter, which he found difficulty in ob- 
taining suitable for the purpose, and high-priced. 
The fibre of the cloth was destroyed by the pressure, 
making the process expensive; otherwise it was a 

To overcome these objections, he devised and con- 
structed a sand-fiTter inside the barrel, which lasts 
about one month, and then has to be replaced, when 
subjected to a pressure of 20 to 30 lbs. per square 
inch. He gives a description of this filter in vol. 
LX of the Engineering and Mining Journal, p. 274. 
Mr. Roth well advocates this filter which works 



satisfactorily. It is one of his inventions and 
we believe it is considered worthy of universal 
adoption, although the mechanical construction seems 
to be faulty on first appearance; but when the 
barrel has been in motion a while the swash, which 
must be considerable at first, will probably be over- 
come by the ore remaining against the inner periphery 
of the cylinder. The question of time versus 
economy in filtering is one of considerable moment, 
and yet to be fully demonstrated: with slow filtering, 
time is consumed, but less cost entailed; with quick 
filtering, less time is required and more cost added to 
the process. The sand-filters require replacement as 
well as the filters placed in the barrel, but they are 
more readily repaired and at much less cost. They 
do not require power, but power after installation o( 
a plant does not add much for filtering, and is not 9 
separate expense; it belongs to the barrel. 

The Plattner process requires a filter in the bottom 
of the tank, in which the ore is leached. Upon the 
floor of the tank, which is slightly inclined for drain- 
age, are laid f-inch strips of wood about one foot 
apart. On top of these and at right angles, with one- 
inch spaces between them, 6-inch boards are placed. 
Upon this false bottom loose pieces of quartz rock or 
clean gravel are placed. On these finer pieces 
layers until the top layer is clean fine sand. Upoi 


this sand, at right angles to the false bottom, boards 
are laid quite close together, as from these boards the 
ore must be shovelled from the tank after leaching 
and drainage. 

The same difficulties will occur with the use of this 
filter as in the previous mentioned sand-filters, which 
can only be remedied by shovelling out the quartz 
and sand and laying a new filter-bed. 


The liquor from the filter-beds is conducted or 
pumped to storage- tanks. If the liquor be muddy 
after passing the filter-beds, or if it contains impuri- 
ties in suspension, it is treated with sulphuric acid to 
precipitate them in these settling-tanks. The time 
for the liquor to remain in these tanks will depend 
upon the clearness of the solution ; not less than two 
hours and sometimes 24 hours may be required. 
These tanks are of sufficient size to hold the liquor 
from one day's run of the filters. The accumulations 
of liquor in these stock tanks is drawn off as desired 
for the precipitation-tanks. 

These latter tanks are usually not over 4 feet deep 
and 6 feet wide by 8 feet long, and of sufficient num- 
ber to allow the precipitate to settle three days. 
Each tank of the above size will hold liquor from 3 
tons of ore, and consequently a 60-ton daily plant 
would require 60 such tanks and occupy a floor-space 
of 4320 feet, allowing one foot between rows. This 


floor-space can be economized by making the tanks 
longer and wider, but they should not be made 
deeper. With vats 12 X 16 feet, or 6 X 32, or 8 X 
24, the floor-space required will be, with one foot 
between tanks, 3600 square feet. When made deeper 
than 4 feet cleaning up becomes unhandy. 

Precipitation-tanks are lead-lined to avoid leakage, 
and lead-lining, not being very stifT, requires skilled 
work to avoid leakage when tanks are made large. 
After the precipitation-tank is nearly filled with liquor 
from the stock-tanks it is treated with ferrous sulphate, 
with the following reaction; 

2AuCl,+ 6FeSO, = 2Au + Fe.Cl. + 2{Fe,0,.3SO,}. 

The precipitated oxide of gold is a dark reddish- 
brown powder, brought about by an interchange of 
metals in the presence of oxygen. The ferrous sul- 
phate (copperas) should be made fresh daily for use, 
it being converted by the oxygen of the air into 
various basic sulphates if allowed to remain exposed 
any great length of time. Its precipitating qualities 
will be weakened where Fe,{SO,)„ or ferric sulphate, 
is formed in particular. 

To manufacture ferrous sulphate (FeSOJ, scrap 
iron is thrown into a wooden tank, and sulphuric acid 
added until hydrogen is evolved. After standing 
some time the liquor is drawn off for use, and more 


water, iron, and sulphuric acid added for the next j 
day's solution. 

It requires about three days to settle the gold pre- | 
cipitate, which is formed in a very finely divided 1 
brown powder. The fluid in which the gold is sus- 
pended has a blackish-blue color by transmitted light. 

To ascertain if precipitation be complete, the solu- 
tion is tested every 24 hours. 

The absence of chlorine and a sweetish odor are fair 
indications of a complete precipitation, but for a 
certainty a small quantity of the liquor is stirred 
thoroughly in a beaker with FeSO,. When the pre- 
cipitate in the tanks has settled, the liquor above is 
either drawn or siphoned off, a fresh solution from 
the stock-tanks admitted, and again the copperas 
solution added. At stated intervals the settled pre- 
cipitate is taken up from the precipitation-boxes and 
placed in smaller lead-lined boxes, where it is settled 
again, and what little liquor remains siphoned off. 
The filtrates are then well washed with boiling water 
until free from iron salts, after which they are col- 
lected on filters, dried, and melted into bullion. The 
bullion can be raised to 990 + degree of fineness 
where care is used in skimming. Borax and soda are 
usually used as a flux in this melting. 

A more recent method introduced by Mr. Werner 
Langguth presents some advantages over the above 


method, which we believe will in time supersede the 
ferrous sulphate method. A description given by him 
of the process as carried on at the Golden Reward 
chJori nation- works is found in vol. XXI, p. 314, of 
th? A, I. M. E. Transactions. The disadvantages of 
this process are: Impure bullion, and extra work in 
refining on account of the gold precipitate being in 
the form of gold sulphide; also that other impurities 
are thrown down by the hydrogen sulphide used for 
precipitating the gold; and, finally, the intricate ap- 
paratus suggested, as shown in Fig. 6. 

The advantages of this process are economy in 
space for precipitating-tanks; quickness in pre- 
cipitating, and recovery from the auric chloride solu- 

The trichloride of gold solution is pumped into a 
tank, PPT, which is raised about 25 feet above the 
filter-pump, FP, for head. We do not see the advan- 
tage of this arrangement, especially when compressed 
air is used. This tank has a capacity of 7000 or 
more gallons, say of a size lO X 12 X 12 feet, made of 
strong two-inch pine plank, lined with light sheet 
lead. The generators, G, are two in number, made 
of boiler-plate, and capable of standing a pressure 
of 150 lbs. to the square inch. Their size is about 
2^ feet in diameter by 4 feet high. The shape is 
cylindrical, with cylinder-heads securely bolted to the 


shell and provided with manholes. One generator 
is for the production of sulphurous acid (SO,), and 
has an iron pan on a tripod for the reception of sul- 
phur, which is burned in this generator to produce the 
gas. It is not lead-lined. 

Fig. 6. 

The other generator is for the production of hy- 
drogen sulphide (H^S), similar in size and construc- 
tion, but lead-lined, and has no tripod and pan. 

Both generators are connected with air-pressure, to 
force the gases into the precipitation-tanks, and also 
with a discharge-hole at the bottom for cleaning out 
the refuse after each run. 

The pressure-tank (see Fig. 6, /T) is constructed 



of boiler-iron to withstand a heavy pressure. It iS ' 
cylindrical in shape, size 4 X 4i feet, inside measure- 
ment, fitted with manhole and proper threaded holes 
for receiving the pipes from the air- com pressor, and 
also for pipes conducting the precipitants from the 
clean-up to the filter-press. 

The liquor containing the precipitate is run into 
this pressure-tank, and from that into the fifter-press, 
at stated times. The liquor freed from the precipi- 
tate or the liquor above it in precipitation, is run 
directly from the precipitation-tank into the filter- 
press as soon as the precipitate has settled sufficiently. 
A lead pipe leads up from the generators to this tank 
over its side and down to within four inches of the 
bottom, when it turns at right angles and runs across 
the tank. This pipe has holes on the under side 
about one-eighth inch in diameter and six inches apart. 
When air carrying the gases is forced through it, the 
gases rise up through the liquor, and by the agitation 
which it causes soon brings the liquor in contact 
with it. 

The chloride of gold liquor having been forced 
into the precipitation-tank, roll sulphur is placed in 
the iron pan of the sulphurous acid generator and 
ignited. Compressed air for combustion and forcing 
the sulphurous acid gas into the tank is then ad- 
mitted to the generator. The object of this gas is 


not to precipitate gold, but to destroy any excess 
of free chlorine which may be in the hquor. This 
generator forms sulphurous acid by oxidation of 
sulphur as follows: _ 

S + 20 = SO,. I 

The reduction of free chlorine then takes place 
rapidly, as expressed by the formula 

SO, + 3C1 + 2H,0 = H,SO. + 2HCI. 

This changes the color of the liquor from that o( 
yellow to clear blue in a short time, producing a 
white fog of sulphurous acid and chlorine gas, which 
is led up C, a ventilating chimney. When no trace 
of chlorine is detected (see tests for chlorine, pp. 63, 
7i) ^he gold is precipitated by sulphuretted hydrogen 
(H,S) formed in the other generator by the action of 
sulphuric acid on iron matte (iron sulphide). Hydro- 
gen sulphide gas is forced up through the solution by 
compressed air, as in the former instance. The reac- 
tion is expressed by the equation 

H,SO. + FeS = FeSO. + H,S. 

Before the acid is put in the generator twice its 
bulk of water is added. 

The precipitation of gold by the hydrogen sulphide 
takes place according to the following reaction 
aAuCl, + H.S 4- 2H.O = 2Au 4- 6HCI + SO, 



The solution is tested in about one hour to ascertain 
if all the gold is precipitated by filtering the liquor to 
be tested through filter-paper, and adding a few drops 
of FeSO,. When no precipitate is formed on the 
test liquor the solution is allowed to stand two hours, 
and then drawn of! to within 4 inches of the bottom 
of the tank, and passed through the filter-press, 

The precipitation will take about one hour and the 
settling two, the time required to pass through the 
filter-press about three, or a total of six hours to pre- 
cipitate and collect the gold. When this is compared 
with three days, the saving in time is noticeable. 
The tank of 7000 gallons capacity is capable of hold- 
ing the filterings of 20 tons ore where 350 gallons of 
water is added in leaching and washing. 

The clean-up occurs once or twice a month, when 
the collected filtrates from the bottom of the precipi- 
tating-tank are passed into the pressure-tank, and 
from there into the filter-press, where tliey arc dried 
by compressed air. These filtrates contain impur- 
ities, which will require careful roasting and smelt- 
ing to give a bullion from 800 to 930 fine gold, Mr. 
J. E. Rothwell has precipitated gold from solution* 
carrying copper by this method without precipitating 
the copper, which is almost invariably precipitated 
from such treatment in the laboratory,* 

* PoUssium niciate prtcipitales meullic gold ia Bolutioa, Pol 



Precipitation becomes difficult when impurities are 
in the solution, such as lime and magnesium, which 
give bulky precipitates.* This can be obviated by 
the addition of acid, or by filtering through charcoal. 
This latter process is carried on as a method for pre- 
venting the bulky precipitates formed by ferrous 
sulphate from mixing with the gold. Just what the 
reaction is between pulverized charcoal and trichlo- 
ride of gold is unintelligible, but the charcoal is 
certain to quickly decompose it, and collect the gold 
in and upon its surface, H the lime, magnesium, or 
arsenic be fixed or held in solution by acid, they pass 
through at times without decomposition, but not 
always. In the latter case the utility of charcoal as a 
precipitant over ferrous sulphate is nothing — in fact, 
as it adds new complications, is a hindrance, and to 
be avoided. There may be more or less slimes as 
well which pass the filter: these collect mechanically 
upon the charcoal, and when burned with the charcoal 
form with the ash a mixture which requires consider- 
able extra work to get rid of ; then, again, at times the 
lime and magnesium forming a precipitate as well give 
virtually a new gold ore, difficult to handle. 


or soda when added in excess will 1 
being tvarmed and tannic acid added, n 
Freiettiut, p. 191). 
* M. S;" M. Journal, \a\. LX. p. 333. 

:ave Ihc solution clear, but 
ill separaie the gold (Jobnsoa' 



The liquid precipitants have all the same disadvan- 
tage, viz., the trouble necessary in collecting the pre- 
cipitated metal; but gold does not, as a rule, deliver 
itself up from ores as bullion without trouble, and 
that is to be expected. Mr, J. T, Blomfield suggests 
the following plan for gold precipitation : 

He forms subsulphide of copper by fusing sulphur 
and copper together (Cu^S). This is crushed to 
pass a loo-mesh sieve, and is then used as a filter 

The liquor, filtered through copper sulphide, showed 
no gold present upon testing with Fe,SOj. 

He suggests three vessels containing this precipi- 
tant: the first to catch the gold, the second to catch 
any gold which may have passed the first, and the 
third as a possibility. 

The first vessel, Cu,S, becomes fully charged with 
gold before any traces appear in the second. This 
vessel is then removed, the second moved to take its 
place, and the third the second's, while a new vessel 
is added for the third. 

The residue is fused with nitre and borax. The 
reaction he gives as follows : ■ 

3Cu,S 4- 4AuCl, = Au,S. + Au + 6CuCl,. V 

This equation should be changed somewhat, as the 
reaction recorded is hardly possible, since gold will 


not unite with sulphur in the cold, and under such 
conditions as given. The following is therefore ad- 
vanced as the probable reaction : 

3Cu,S + 4AuCl, = 4Au + 6CuCl, + 3S. 



To obtain the metal precipitated in a pure form,] 
that it may be handled in bulk of a known value, it, I 
is reduced by heat, which operation is termed refin-J 

The brown precipitate of gold produced by the ac^l 
tion of ferrous sulphate upon the trichloride of gold isl 
collected, washed on filter-paper, then treated with acid J 
to remove any possible impurities, dried, placed in a 
graphite crucible with some flux — either soda 
borax, and then placed in the furnace to melt. 

Gold bullion is said to be fine when absolutel/4 
pure; it is then termed lOOO fine. To obtain sudi.1 
bullion requires an artist and very fine manipulation; 
to obtain it above 900 fine is not as difficult, especially 1 
from the precipitates of ferrous sulphate; but from I 
the precipitate given by hydrogen sulphide the task I 
is more difficult and the bullion less pure, ranging in I 
fineness from 800 to 950, while in the former case it.J 


may be obtained with less trouble from 950 to 990 

The reddish-brown precipitate of metallic gold ob- 
tained by this operation is washed with warm water 
and filtered to remove any acids or salts of iron pres- 
ent, or any other substances soluble. If insoluble salts 
of metals or substances are present, such as arsenic, 
zinc, copper, silver, sulphur, they can only be re- 
moved by acids to reduce them, and then evaporation 
and washing, or by an oxidizing roast, as practised 
at the commencement, but on a smaller scale, in a 

The gold precipitated by FeSO, is placed in a 
graphite crucible, and with a little borax added is 
introduced into the furnace. The oxygen is driven 
off by the heat, the gold gradually melting, while the 
borax forms a liquid slag upon the surface of the 
molten metal. 

This slag has absorbed the impurities which were 
not soluble in water, and as the slag is lighter than 
gold, by carefully skimming the surface it may be 
nearly all removed. 

The oxide of gold is a peculiar compound, but little 
known or understood. Gold when heated may be 
deprived of oxygen, but it will not unite with its own 
or other oxides. Gold is but little volatile, and may 
be exposed to a strong heat for some time after melt- 



ing; in fact it is frequently boiled. With nitre the^ 
boiling is so marked that larger crucibles are required 
as well as covers to keep it within bounds. The 
opposite is the case when volatile metals are com- 
bined with gold. They when driven off by heat 
carry gold with them ; noticeably is this the case with 
the metals zinc, lead, arsenic, antimony, bismuth, 
and tellurium. To obviate this as much as possible 
the gold must be kept below a boiling-point, and be 
protected by slag, formed from a suitable flux. Gold 
with pure borax as a flux assumes a whitish color in 
melting; with saltpeter or common salt it retains its 
rich yellow color. 

The heat should at first be mild, but may be grad- 
ually increased, and maintained during the melting, 
and for some little time afterwards. The crucible 
with Its contents is then removed, and the gold poured 
into moulds to form ingots of gold. These ingots 
are sent to the nearest assay-office (Government assay- 
office wherever possible), tested for fineness, and sold. 

The assay-offices do not like to accept base bullion 
on account of the trouble they encounter in refining 
it, nor will they pay as good price for impure bullion 
on account of the extra work and chances for loss in 
further refining. 

Mr. Langguth having introduced the improved 
method of precipitating referred to in the last chapter, 


whereby he obtained auric sulphide, was obliged ta 
refine these sulphides after collecting them from the 

Hydrogen sulphide precipitates gold from neutral 
or acid solutions. From the cold solution the pre- 
cipitate is Au,S, ; from boiling solutions, AujS. These 
precipitates are insoluble in acids, but soluble in 
" aqua regia" — a mixture of nitric and muriatic acids. 
If we should use the latter method we would virtually 
have the same experience to go through with as were 
we to use FeSO,, and in the end must use the latter 
precipitant, although the liquor to be treated would 
be much less in quantity. 

The aurous sulphides may be dissolved in yellow 
ammonium sulphide or by yellow potassium or so- 
dium sulphides, but there is nothing to be gained by 
so doing. 

Mr. Langguth places the precipitates and the filter- 
cloth in pans, which he introduces into muffles in a 
roasting-iurnace, to drive off the sulphur, arsenic, and 
antimony, or whatever other volatile substances are 

This oxidation can be accomplished in about three 
hours, when the mass presents a reddish or yellowish- 
brown appearance. If salt roasting could take place 
without loss of gold, purer bullion could be obtained 
bat as it is, care has to be used in first heating to 



avoid loss of gold by volatilization. These roasted 
sulphides are now removed from the muffle, and 
being hard are placed in a pulverizing drum with 
cobble-stones to assist pulverization, after which the 
flux is added in suitable proportions and thoroughly 
mixed with the gold sulphides. 

If the ore treated has been silicious or acid, the 
flux is borax or soda; on the other hand, if it has 
been basic, a silicious fiux of sand or quartz is added. 
The gold mixture is now placed in a crucible, and this 
and its contents placed in the melting-furnace. The 
sulphur remaining from the roast is partially driven 
off by heat and absorbed by the flux, leaving metallic 
gold as follows : 

Au,S,4- 4O = 3Au + 2SO,.* 

After melting, and being kept at a high tempera- 
ture some time, the crucible and contents are removed 
from the furnace and poured into conical moulds of 
suitable capacity. The bullion separates from the 
slag in these moulds as a conical button in the bot- 
tom, from which it is taken when cool, remelted, and 
cast into ingots for shipment. 

The slags contain considerable gold, and are there- 
fore pulverized and separated by water, the gold being 

* The author quotes Mr. Longguth's equBtio 


added to the next melting, while the tailings are 
mixed with lead and metallic iron, and melted in 
crucibles. The lead bullion resulting is cupelled, 
yielding the remainder of the gold. The slags from 
the second melting are too poor in gold to handle. 

No serious losses occur by this method, but slight 
losses do occur, and from what has been said 
previous are due to vaporization and to mechanical 


Plattner's application of chlorine gas to cold 
gold is the foundation of the process. Mr, G. F. 
Deitken was the first to make a practical and commer- 
cial success of the process in the United States, at 
a mill situated in Grass Valley, California, The pio- 
neer works of the East were under the charge of the 
present editor of the Engineering and Mining Journal, 
Mr. R, P, Rothwell; the;- were situated at Deloro, 
Canada, and were worked by the Mears process. The 
pioneer works of the South were at Haile Gold Mine, 
South Carolina, where the Theis method was brought 
out. The pioneer works of the West, as far as barrel 
chlorination is concerned, is the Golden Reward Chlo- 
rination Mill, Deadwood, S. D. 

The tank-lixiviation seems to have made way 
almost entirely for the barrel-chlorination process, and 
the Mears for the Theis. 

The barrels were originally constructed to contain 
one ton, but are now made to hold as high as ten tons. 

r&sumS of cffL0Ri2fAr/0N: 99 

the latter size being several hundred dollars !ess in cost 
than two smaller barrels of the same capacity. Thej 
are also just as efficient and are more readily operated, 
requiring also less space than two separate barrels oi 
the same capacity. 

The improvements which Mears made over tank- ' 

chlorination were chiefly those which economized in , 

time. He based his process upon pressure, to force 
the chlorine to attack the gold and, further, to mix 
and turn up the ore; that the chlorine gas might have 
more opportunity to do so, he rotated the barrel. By 
these improvements he reduced the time from three 
days to six hours, and also the attendance proportion- 
ally. Mr. Theis found the Mears process too cum- i 
bersome, and introduced the chemicals into the barrel, 
which not only generated the gas, but produced pres- 
sure sufficient for all purposes. This was a most im- 
portant improvement, since it overcame trouble and 
expense engendered by the generation of gas outside 
the barrel. It also overcame several mechanical de- 
fects incident to such generation, as well as doing 
away with the pressure-gauge and its leaky goose-neck 

Mr. Rothwell's addition — the filtering from the 
barrel under pressure — was the next_ improvement; \ 

and finally may be added Mr. Langguth's precipitation 


These improvements have increased the capacity 
of the plants from 5 to 150 tons daily capacity, and 
at the same time decreased the cost of operating, and 
increased the extraction in a given time. This not 
only speaks well for the process, but certifies its 
usefulness. The original Theis plant is still in opera- 
tion, and we are informed has paid over $500,000 in 
dividends from low-grade sulphur ores. 

The mill site and locality will determine the ar- 
rangement of the mill, machinery, and labor-saving 
appliances to be adopted. 

The advantages of a hillside are not so great as 
would warrant the building of a long tram-road to 
obtain a gravity fall, as in gold or silver milling, 
since the arrangement must be as automatic as possi- 
ble to avoid elevating machinery. But in our case 
the ore will have to be conveyed to the dryer bin 
either on a level or elevated, and from the dryer to 
the rolls and from them to the concentrators, and 
finally to the roasters, cooling-floor, and leaching- 

The preference would be a crusher which can 
handle 30 to 40 tons per hour, this being passed 
over |-inch grizzlies to two smaller crushers capable 
of handling the product — say 100 tons daily for the 
plant. Of the 100 tons passed to the large crusher 
30 per cent will be of a suitable size for the dryer. 


This relieves the small crtishers of 30 tons of ore. 
The small crushers will produce 30 per cent of ore 
which will screen J inch, and thus relieve the dryer 
of 21 tons daily, for the moist ore will generally be 
found in the first crushings and screenings. The 
small ore from the second crushers can go direct 
to the rolls; the finer ore to the dryer wiil also be 
treated quicker; and that dried ore mixed with the 
fine direct from the crushers will screen readily. In 
some cases by drying ore of small size thoroughly it 
has been found that ore crushed to J-inch mesh will 
pass the rolls and screen as high as 70 per cent through 
a 20-mesh screen. The advantage of dryers and the 
fine crushing thus becomes doubly apparent. The 
finer the ore delivered to the dryer the quicker it is 
deprived of moisture and the better the product of 
the rolls. 

The ore which passes through the coarse rolls 
should screen at least 25 per cent 30-mesh, 25 per 
cent -j'^-mesh, and the balance between ^ and J. To 
throw J-mesh ore on a No. 30 screen is very destructive 
to screens; for this reason two screens are used, the 
inner being ^-mesh, the outer 30-mesh. The product 
passing the ^-mesh goes to the fine rolls, the balance 
back to the coarse rolls — possibly 25 percent. The 
same proportion will probably hold true in the case 
of the fine rolls, 25 per cent being fine enough to pass 



the 30-mesh screen with one pair rolls, while 50 per 
cent would pass two pairs rolls with one elevating. 

The use of two pairs coarse rolls and two pairs fine 
rolls is therefore economy in power, screens, and roU 

If concentrating machinery be used and ore crushed 
to 30-mesh separators and jigs, fine and coarse may 
answer; but as there is much ore above 30-mesh, it 
may be necessary to use separators and vanners in 
preference to jigs where the ore crushes easily. 

In the case of clayey ores rolls will not answer, and 
either Chilian mills, Huntington mills, or stamps 
must be used for crushing, and this is followed by 
vanner concentration. 

If the gold be coarse and can be saved in part by 
amalgamation, Huntington mills or stamps may be 

If fine crushing is required, Chilian mills or stamps 
must be used, the limit of roll crushing being 30- 
mesh screen. 

The power will consist of a first-class automatic 
cut-off engine 150 H.p. being sufficient for a 100-ton 
mill. This should have feed-water heater in prefer- 
ence to condensing apparatus, unless water is very 
valuable and needs to be economized. There should 
be an electric-light engine, and a smaller auxiliary 
engine to run the chlorinators and furnaces at night, 


in case all the power were not needed. This latter, 
while not necessary, will be found to be economical in 

The boilers and feed-pump are a part of the plant. 
Flue-boilers are not as economical as tubular boilers, 
although the latter require more attention. 

The dryer is a cast or wrought iron revolving cylin- 
der, similar in construction to furnaces, with cast-iron 
shelves which pick up the ore and shower it through 
the flames. They are either one diameter the whole 
length, with jack-screws to elevate one end, thus giving 
a quicker or slower discharge as required ; or they are 
made larger at one end than the other, to work the ore 
forward as it is dried. The dryer is rotated on rollers, 
similar to revolving roasting furnaces. 

The ore is fed in at one end and is dropped into a 
pit at the other, from which it is conveyed automati- 
cally by elevators or scraper lines to the pulverizers. 
The storage-tanks and other appliances of the plant 
have already been mentioned. 

The laboratory is a necessary appendage, which 
should be fitted up with assayer's outfit, also a roast- 
ing and smelting furnace, and in case of amalgamation 
an amalgam retort. 

Pumps also may be required about the plant, and 
storage-room for chemicals as well. 

The screens are either hexagonal or round, made 


da ^J 


in sections that wire cloth may be readily replaced i»" 
frames which fit to the screen, spiders, and frame. 
They are of two compartments, as mentioned, the in- 
side screen being heavy wire netting or metal plate, 
with holes punched in it. The outer screen is wire 
cloth ; at least one foot should be allowed between the 
inner and outer screens.* A Root blower will prob- 
ably be required to keep down the dust from the rolls 
and screens. 

Salt-storage bins should be in the vicinity of the 
furnaces where chloridizing roasting is practised, and 
these bins should be of sufficient size to carry a good 
supply unless it can be obtained readily. Automatic 
feeders should be used for crushers and pulverizers; 
also automatic machinery, as far as details wilt permit. 

* The Bertbelet separator is advanced by H. F. Brown as a gub- 
slitute for revolving screens. 



The factors which enter into the cost of the process' 
preclude giving a cost which will cover every case. 

a. These are cost of mining and transportation to' 
the mill — two items which will vary according to the 
character of the rock, the depth of the mine, the water 
encountered, and the distance of the mine from the 
mill. This cost will be increased or decreased by the 
above, and further influenced by the situation of the 
mine and mill with reference to the transportation of 
supplies and product from railway connections. 

b. The cost of milling enters into the calculation, 
which depends upon the character of the rock, the 
ease with which it is crushed, and its arrangements in 
detail for close and automatic work. 

c. The cost of concentration and the amount of 
concentrates saved, together with the degree of care 
taken to obtain clean concentrates for roasting, 

d. The character of the furnace, and the degree 
of desulphurization dependent upon the amount of 




sulphur in the ore, or other substances which need to 
be eUminated, determine the cost in this department, 
which must necessarily differ in different localities or 
for different ores in the same locality, 

e. The cost of chemicals will vary according to the 
facilities by which they may be obtained at the mill, 
and will also vary for different characters of ores, thus 
making their cost indefinite. The labor required ia 
the laboratory for precipitating and refining is also 
indefinite consideration, 

f. The superintendent's and office expenses will vary 
for each mine, a good manager generally, however, 
saves his wages several times over during the year. 

Much is said about this process for low-grade ores 
and for the benefit of those contemplating the use of 
this process on low-grade propositions we would sug- 
gest they advise with a mining engineer before 
doing, and not to attempt it on ores carrying less 
than $6 pec ton of gold if the mine be not well 
developed, in which latter case with favorable circum- 
stances the process should be remunerative, 

Mines which are but partially developed do pt 
offer enough stoping ground for steady supply 
suitable ore, and development is always more expea- 
sive than mining. With mines well opened on plenty 
of stopes the mining expenses are reduced, and 
than cover the cost of development. The average 





cost of mining will be about $1.45 per ton where 
power drilling, hoisting, and pumping is carried on, 
which figure also includes timbering. 

The dumping and tramming to the mil!, and the 
dumping there, will add ten cents per ton to the above 

The milling will average on hard rock where stamps 
are used $1, and the concentrating and the handling 
of tailings and product about 50 cents more. 

After concentration the cost of roasting may be 
considered, and this will vary from 30 cents in the 
Cripple Creek district to $3.75 in others. At the 
Haile Mine, where wood and labor are cheap in com- 
parison with other localities, the cost is placed at 
$2.62, for a ton of roasted concentrates, oxidized to a 
"dead roast " so that but 0,35 per cent of sulphur 
remains in the ore. 

Then in order comes the cost of chemicals, which 
will vary from $2 to $3 per ton of concentrates, while 
the labor and other expenses will add about $5 to it. 

In taking these different items up in detail, it must 
be borne in mind that we are dealing with concentrates, 
and, further, roasted concentrates. 

If we have an ore running $6 per ton as it comes 
from the mine, and wc can concentrate 90 per cent of 
the value, the ore should assay $5 .40. If the ore runs 
33i per cent in sulphur, one ton of roasted 




require i.3tonsof concentrates — possibly more ; or I)j 
tons of raw ore will make i ton of roasted i 
trates. The value of the roasted ore will also 1 
raised, by its quantity being lowered, provided no loss 
occurs other than mentioned, the value of 13 tons 
mine ore; i^ tons o( raw concentrates or i ton (^^^H 
roasted ore, will be $70.20. ^^^| 

With miners' wages at $2.50 and coal at S5, if 2.^^^H 
tons of ore are drilled, shot, cobbed, loaded, and 
hoisted per man employed at the mines the work is 

The cost then would be about as follows; 

Labor $1.00 per ton. 

Powder, fuse, and caps 15 " " 

Fuel 15 " " 

Timbering 15 " " 

Supplies 10 " " 


Or $19.15 for one ton of concentrates. 

Adding 10 cents per ton of mine ore for transportaJ 
tion, which includes wear and tear on rolling-stock and 
motive power, oil-waste, runners and dumpman's 
wages at the mill, the cost for 13 tons is $1.30. 

With wood at $2.50 per cord and labor $2.00, thd 
cost of roasting one ton of concentrates would b^— 1 


\ cord wood at $2.50 $1.25 

12 hours* labor at 20 cents 2.40 

Motive power 35 

Cost of roasting 1.3 tons concentrates . , . . $4.00 

The cost of milling would be, with 60 stamps, in 
hard rock: 

Labor $0. 35 

Supplies 02 

Fuel 25 

Machinery 10 

Oil and waste 03 

Illumination 02 

Lumber , 02 


Or for 13 tons $10.27. 

The cost of concentration would be about as fol- 

Labor $0.26 

Repairs • • • • • o. 10 

Supplies • o. 10 

Fuel 0.15 

per ton, or $7.93 for 13 tons ore. 


The chemicals may be more or less than the quanti 
ties given ; we have endeavored to take an average : 

30 lbs. chloride of lime at 3 cents .90 

35 ** sulphuric acid (H^SO J at 3 cents 1.05 

10 * * HjSO^ for settling-tanks .30 

10 * * H,SO^ for ferrous sulphate • . . . .30 

40 '** salt at \ cent .20 

Labor of 2 men at $2 4.00 

Labor of i man at $3.50 3.50 

Motive power .35 

Laboratory expenses. . , , ^ , 1.50 

Cost of chlorinating $12. 10 

We have not added the proportional part of super- 
intendent's and office expenses, which would reach 10 
cents per ton raw ore, or $1.30 per ton of concentrated 
roasted ore. There is still another item, such as 
amortization, which may be placed at 25 cents per ton 
of concentrates roasted. Our cost is then as follows : 

Mining 13 tons ore $19.15 

Transportation to mill, etc 1.30 

Milling 10.27 

Concentrating 7.93 

Roasting 4.00 

Carried forward 42.65 


Brought forward $42.65 

Chlorinating and recovery 12.10 

Superintendent and office expenses.. 1.30 

Amortization 3.25 

Total cost of chlorinating one ton 

roasted ore. . . , $59.30 

Or per ton of mine ore $4,56, 

The total value of the ore concentrated is $70.20; 
as we cannot extract all of tliis value, only about 
92+ per cent, we have for a margin of profit the dif- 
ference between S64.58 and $59.30, or $5.28— about 
40 cents per ton of ore mined. 

This margin we consider too small for mining and 
milling for safe work, as it docs not allow lOpercent 
for contingences and requires that lOO tons be mined 
daily for 155 consecutive days before the interest on 
the investment, if it be $100, OOO, is paid. With a free- 
milling gold ore this profit could be increased from 
$52.80 on a 100-ton daily mill to $1 16, and only ex- 
tract 60 per cent of the gold ; the remainder in the 
tailings could then undoubtedly be concentrated and 
treated at a profit sufficient to warrant the expendi- 
ture of the money on the additional plant. 

The first cost of installation is high, because of the 
necessary crushing, concentrating, roasting, filtering, 



and precipitation requirements. A complete < 
trating plant for go tons daily, which includes crush- 
ing plant, will cost, according to its elaborateness, 
between $30,000 and $40,000. 

For chlorination must be added the furnaces and 
other paraphernalia equally expensive, which with 
buildings will bring the cost up from $6o,000 to 
$80,000. The process is not able to recover coarse flake 
gold, and does not'recover silver, but under certain 
conditions it is the best process known. It has in its 
favor the treatment of high-grade sulphurets with a 
high extraction. In this respect it is superior to 
cyanide, even when the ore is roasted for both proc- 
esses. It covers a fleld distinctly its own, and has 
certainly come to remain as one of the metallurgical 
operations of the future. 

In some instances tailings can be treated at a very 
low figure; in others the cost of roasting varies from 
30 cents to $4.60 per ton, and the chlorinating from 
$3. 1 8 to $4.60 per ton of concentrates. The Golden 
Reward has reduced the cost to $3, while the Haile 
Mine cost has been reduced from $4.84 to $3.50 per 
ton. We may expect, therefore, greater reductions 
when chemicals and roasting are reduced in cost. 

For the benefit of those who inquire why this proc- 
ess has not been more generally adopted, it should be 
stated that those who run mines are not capable of 



carrying it on, and, knowing their weakness, let it 
alone; again, parties having mining machinery to sell 
advise the use of their machinery rather than chlorin- 
ation; and, lastly, mine owners, thinking they will ■ 
have to pay higher salaries to good men, are willing I 
to suffer loss of gold rather than do so. Other | 
matters, such as inability to purchase the necessary 
plant, must be considered as a further hindrance to its \ 
introduction. For that reason custom mills do a fair | 
business in some localities. 

Wherever chlorination has been introduced it 
mains, thus testifying to its worth as a means for | 
extracting gold from refractory ores. 


For stamps, i.a to 3 gallons per stamp per minute. 
" plain-belt vanners, J to 2 gallons per minute. 
'■ corrugated -belt vanners, i^ to 3 gallons per minute. 
Note. — To the vanner water, which is clear, must be 
added the pulp from the stamps. 

For boilers, 8 gallons per horse-power per hour, .^H 

" each settler, i gallon per minute. i^| 

" " pan, 2 gallons per minute. 

" chlorinating barrel, 80 to 100 gallons per ton of ore. 
Wash-water, 200 to 300 gallons per ton of ore. 
Of the above water, 50 per cent of that used for engine 
can be condensed and used over again. 

Of that water used by stamps, settlers, and pans, all but 
20 per cent may be settled and used over again. 

The chlorinating and wash water cannot be used again 
in the leaching or washing process where ferrous sul- 
phate or hydrogen sulphide is the precipitating agent, but 
it may be used when charcoal is the agent. 


7000 grains ^ avoirdupois pound. 

5760 " = troy pound. 

Av. lbs. X 1.21527 = troy pounds. 

" ozs. X.9115 = '■ 

One gramme = 15.433 grains. 

One kilogramme = 2.2047 pounds av. 

One " = 2.6778 " troy. 



Meter = 39.3710 inches. 
Millimeter — -03937 " 


I ft. = 12 ir 
I yd. = 36 
I fathom = 6 f 
I pole = M 
I furlong = 660 
I raile = 5280 

ch = -0254 meters. 
ches = .3048 " 
" ^ -9144 " 
= 1.8287 " 

= 1609.351 " 


To change millimeters 
the number of meters by 

nto decimals of an inch, m 


^ of an inch 
A " " " 
tS " " " 
\ " " " 
1 " " " 

s, in decimals, .015625 
' " " .03125 
' " " .0625 

' " " -'^5 
' " " .25 
' " " .50 




Cent. 1 

R^au. 80' 

32 J 

2i2"-32 = i8o and m=l=i-8 C, or \\« =1=2.25 Rfeu. 
Temp. Fahr. = (? + 32) Cent, or (f + 32) Reau. 
" Cent. = (S - 32) Fahr. or f Reau. 
" R6au.= (i — 3?) Fahr. or } Cent. 

To convert Fahr. to Cent.: Subtract 32 and divide by 1.8. 
To convert Fahr. to Reaumur: Subtract 32 and divide by 2.25. 
To convert Cent, to Fahr.: Multiply by 1.8 and add 32 to 

the product. 
To convert Cent, to Reaumur ; Deduct |. 
To convert Reaumur to Fahr.: Multiply by 2.25 and add 32 

to the product. 
To convert Ri^aumur to Cent.: Add \. 




Wire screens take their numbers from the meshes in the 
linear inch; slotted screens, from the number of needle 
used in punching the plates. The slots are usually -J inch 
long, running diagonally, but can be obtained either run- 
ning lengthwise or crosswise of the sheet. 

Wire screens pass a greater product than slot-screens, 
but wear faster. 

of Needle. 

per Inch. 




















of Slot, 

























Higher numbers of wire screens can be obtained of the. 


Faint red 960° F. Sis'* C. 

Dull " 1260° F. 680'' C 

Cherry-red 1650° F. 898** C 

Yellow or orange . 2010° F. 1099** C. 

White 2370° F. 1299° C. 


The following metals volatilize below red heat : Arseric, 
at 35^° F- or 180° C; mercury, slightly at ordinary tem- 
perature, boiling at 680° F. or 362° C. 

The following metals volatilize at red heat : Pot.i^-; 

sodium, tellurium, magnesium, zinc. 

The following metals volatilize at white heat : Zinc, anti- 
mony, lead, liismmh, 

Metals which give up their oxygen to heat : Mercury, 
silver, gold, platinum, palladium, rhodium, iridium, and 

Metals which retain their oxygen at high temperatures, 
and cannot be reduced by heat alone ; Potassium, sodium, 
calcium, magnesium. 
































106. G 

very high h. 














very high h. 

■ 36' 

very high h. 
high heat 


" " 





Aaron, C. H • 28 

Ammonia test for CI •••• 63, 73 

Aqua regia.. .^.•... 5 

Arsenic....... •• •••••.............• 23 

Assays 12 

" oflSces..... 95 

Auric chloride 3, 60 

'* oxide 93 

'' sulphide • • 90 

Austin smelting process • . . • 33 

Barrel charging ••••.••• 71 

" chlorination 66 

" construction. • 69 

'' pressure in 81 

Bismuth 23 

Bleaching-powder 4, 61 

Bromide 2 

Bruckner's cylinders 48 

Bullion 83, 94 

Butters, C 28 

Calcium carbonate ..•••• • 65 

chloride 5, 65 

hydrate 4 

sulphide • 64 

Charcoal reaction 89 

Charging the barrels 72 

Chloride of calcium 5, 65 

" " gold 3 

" " silver 3,23 

** "sodium • 7 






1 20 INDEX. 


Chloridizing roasting 5, 7, 22 

Chlorine 3, 72 

" tests for. • 63,77 

Chlorination i, 17 

" advantages of ill 

barrel 66 

" cost of 112 

" plant for 62,111 

ore for • 11, 20 

recovery by •••••••• 64 

roasting for ••••• 22 

Chloro-aurates • • • 60 

Christy, Prof • •••• 29 

Cobalt 24 

Collection of precipitates « 83 

Concentration 8, 16, 17, 102 

" cost of • 120 

Construction of barrels 68 

'* filters 75, 79 

" tanks 62 

Copper sulphides • 23» 90 

Cost of chlorinating ..••••• 18, 112 

" '* chemicals no 

" " concentrating 109 

'' " milling , 109 

" " mining 106 

" " plant Ill 

" " roasting • 112 

Crushing ores • 12 

Cyanide 2, 112 

Dead roasting 22, 32, 37 

Dead roast, test for • 34 

Decanting the liquor 77 

Decomposition of sulphates • 35 

Dryers • 56,100,102 

Experiments by Aarons, C. H 28 

" Butters, C 28 

" ** Christy, Prof 27 

INDEX. 121 


Experiments by Plattner • 27 

*' Stetefeldt. C, A 28 


Ferrous sulphate 76, 82 

*' " manufacture of 83,92 

Filtering 25, 75, 89 

precipitates 85 

pressure in 75, 78 

time of 77 

with sand 75 

Fine ore 24 

Fluxes 83, 90 

Furnaces, roasting 37 

Fusion 21 

Galena 23 

Gold chlorides 3f 60, 76 

fineness 83, 88, 92 

loss of •••••• 26, 32 

oxide 82, 93 

precipitation. 87 

refining •• 92 

recovery 64 

relative solubility in Br, CI, Cy ••••••.« 2 

sulphide • 84 

soluble in 2, 5 

test for 83, 88 

volatility of 93 

Hydrochlo-auric acid ••••• 6 

Hydrochloric acid .••• 4 

Hydrogen sulphide 87 

Howell furnace 53 

Iodine test for CI 85 

Iron sulphides ••••••• 22 

Laboratory expenses no 

Langguth's methods 84 

Leaching ..«•• •• 25. 60 

122 INDEX. 


Leaching, partial • •... 73 

'* time of 63,73 

Lime, slacked •* 4 

" precipitated 64 

Lixiviation • I, 10 

Loss by roasting • 33 

** of gold, see Gol^. 

** ** silver, j^^ Silver. 
Low-grade ores • •• • 10 

Mears process • • 65 

Mechanical roasting • 37, 57 

Melting 93 

Metal mining 9 

" " costof 106 

" salts 94 

Mercury 23 

Milling, cost of 7 

Mining advice 10, 106 

Muffle-roasting 29 

Muriatic acid 4 

Newberry-Vautin 67 

Nickel 23 

Nitrate of silver test 85 

Ores, drying 5i» 63 

" fineness of 24 

leaching 31 

loss in weight of 34 

low-grade 10, 105 

of base metals 25 

preparation of 11, 22 

refractory • 16, 22 

roasting of. 20, 33 

4 « 


" treatment of 8 

" sulphide 7> 16, 23 

Oxland furnace, see Furnaces. 

Oxidation 3, 7, 20 

Oxides of gold 82, 93 

Oxidizing roasting 40 

INDEX. 123 


Process, chlorination, see Chlorination. 

" choice of i, 18 

" cyanide I, 18, 112 

'* Mears' 65 

" Newberry-Vautin • •••• 67 

• • Planner's 6, 61 

" Russell t 1,23 

" Theis* 65 

Phosphorus • . . 24 

Pile-roasting •••• 36 

Precipitates, collection of . . • 83 

" Langguth's 83 

*' time for 81, 89 

*' treatment of 83.93 

Precipitation 81 

•' by FeSO* 82 

by HaS 65, 84. 87 

" difficulties 88 

* ' fractional 88 

of gold 81 

Potassium nitrate 93 

'* sulphide • 96 

Pressure in filtering 75 

" " process • 67, 75 

Pulverizing sulphides 90, 96 

Rabbles 24 

Recovery of gold 73, 75 

Refining • *... . 94 

Refractory ores, see Ores. 

Reverberatory furnace 38 

Roasting, see Furnaces. 

" cost of 110 

" dead 22,32 

" furnaces 36 

" in piles 37 

" muffles 27 

" precipitates • 93 

" ores 22 

*' temperature in ,.,..,.,.»., » » 30 


124 INDEX. 


Roasting, temperature test ••••••••••• 34 

theory of .••••••••.;. 35 

time of 32 

Russell process i, 23 

Salt 7, 26, 34 

Sand filters 75 

Settling tanks • 64 

Silver chloride 3> 20, 23 

" " loss of 22 

Slags 93 

Soda and tannic acid 91 

Sodium chloride 3, 21, 26, 

'* sulphide 96 

Storage tanks 81 

Sulphates 33 

Sulphides 16, 23, 64 

" and heat 36 

Sulphuric acid a fix 81 

" " for chlorine 4* 16 

" " FeS04 76,82 

" •' HaS ..;. 88 

Sulphurous acid generator 85 

Sulphuretted hydrogen \\S,,. 87 

Tellurides • 23, 28 

Temperature in roasting 30 

Test for chlorine 63, 73, 76 

" •* gas ... 68 

" " gold 74,83,88 

*' '* roasting 34 

" " wash-water 76 

Theis process 65 

Time in filtering • • 77, 79 

" leaching 63,73 

precipitating • 85, 89 

roasting 33 

Titanium 39, 100 

Treatment of precipitates • 83, 93 

** " ores 8 

INDEX. 125 


Treatment of slags • •••• • ••••••• 93 

Trichloride of gold • 4* 76 

Vein rock • ••• 12 

Wash-water * ^77 






New York. 
Lohdon: CHAPMAH & HALL, Lihitto. 



Budd and Hansen's American Horlicultun.1 Manual: 

Part n. Systematic Pomology 


Mttyn«rd'» Landscape Gardening as AppUed lo Hon.. Decoration. 
■ McKaj and Laiseo'a Frinciplea and Piactice of Butter-making . 


loeeetB Injurious lo Garden Crops. (In preparation.) 
InsMts Injurine Fruit?. (In prejiaration.) 

WoU's Handbook tor Farmers and Dairymen 



BWnnite'B Planning and Construction of Aroericau D.eaties Bvo, 

Wa^ Madera American Sctool BuiWinES * 

itilallns of Buildlnci. . 

: »Bt P. 

•Gthdc'b Stiuctui 
BoUy't C»nii!ntera' and J 
Jotan»a'( SUllcB by AI«< 


Srupbic HetbodB 

Builders' pocket-book. Rewritten Edition 

IBS for BuiMing and Socaration 

jliic Uincrals: Their Oecurr«ne« and ITseB 



Palton's Practical Tr 

Peabody's Naval Arcbitecture 

Rice's Coocreti -block Himuiacture 
Ricbcy'B Handbook for Superintend! 
• fiuildint Mecbar 

workers' Editio 
Sabin'K InduBtrial and At 

SoDdericker'i Graohic Statics witb Applica 

&1 Jurisprudence ........,...! 


The World's CDhimbiu Exposition ol 1893 Large 41a, 

Bernadou's Smokeleaa Poo 


• BruTa Teit-book Ordna 
CbMe'8 Screw Propellers a 
CkJke's Gunner's Eiamin 


.d Squiei 

's Elem 

I of L 


ler, Hitro-ce11uk>se. and the Theo 

le PropulslOD. 

in the Uilitary Law ol United St 
ilry Outposts Duties. (Can.).. 


De Brack's Ca' 
Dltti's Soldier' 
"Dredge's Modern French Artillery.. 

Durand's Resiataoce and Propulsion of Ships 8to, 

■ Dyer's Handbook of Light A 
Bissler's Modern High Eiplosi 

•Fiebeger's Teit-book on Field FoitificatlaD Small 8vo, 

SaniiltoB'i The Cimner'a Citechlun i^mav 

^Mftt't SkauaiMf SvrM ImUm. *»« 

It Foni&CBtions. 1. 

• ElemontB o( the 

Matcalf' s Cost of Manufactures— Ani 

Murra;'B iDfautry Dcill ReeulH lions. 
Niian's Adiutsnis' MacuaL 

the Admlni«tr*tloo 


tlps's Prsctical Marioe Siirve;lu|. . . 

^Il'a Arm; Officer's Eiainiaec 

?e's Art of SubBistiug Armies in Wst 
PDole'3 Manual of Bayoae 

1 Musketr 

• Walke'a Lectur=5 on Eiplosives. 

Weaver's Military Eipioslvca , . 

"* WliHler's Siege Operations and military Mining 

Wlnthrop's AbrideniEnt of Miliiaiy Law 

Woodhull's Motes on Military Hygiene iBniD. 

yo"nf '» Simiile Elemonts of BavigBtion. ifimo, mo 

al Laboratory Eiperi 

al MethodB-of Ore Analysis. 

Low's Techr 
Miller's Mai 

IQnet'a Production o[ Aluminum and it 
O'Drlseoll's Dotes on the Treatment ol 
Rlcketts and Miller's Holes on AKayin 
Kohine and Lenglen's Cyanide Industi 
TJlke'B Modem Electrolytic Copper Rel 

■s Cyan 

in Proc. 


Comstock's Field Astronomy for Engineers 

DooUttle's Treatise on Practical Astronomy 

Gore's Elements of Geodesy 

Haylord's Teit-book of Geodetic Aatrouomy 

Merriman's Elements of Precise Surveyine and Geodes] 

• MichJe and Harlow's Practical Astronomy. . , 

• White's Elements of Theoretical and Descriptive Astr 

tiBTanport's Statistical Methods, witl 

Thomi^ and Bennett's Structural and 
IPHternuIer's Coiapendiiun of Gem 

^^Hv ^i^l 









■ Bto 








I as 

' 15 
3 oo 
I so' 

I 5I> 

Alr«rcir»Gei..r.lPr.Delpl«MOti«ueSsT.ih«ts. i»»ithe»s.), ... 

Amnld'i Compendium ol Cbcmiitcy. (Kaiide).) Sms 

Btnudou-i Smoluhu Powder. -Hi Iro-tcUiilose, and Tieory of the C 

Bnuh ind PenfijU'i Honiul of DeMrmiimlive MinenlogT. 

CUmkh's B«l-™g.r M.nnt.ctur<.. (H.U and RoB..) 

Cisftl's Shod CoiuBC In QualilBllTe Chemiciil Analyiia. (ScluefFer.). - - 

DiechKl'B Chemical RncliaDs. (Henlll.) 

Effronl'i Enijmes and their Applications. (Prewott.) 

Fletcher's Practical InatnictionE in Quantitative Assaying wiUi the Bio 
1 iimo. Hio 

Fre«eniiB'. Hantul of Oualitative Chemieal Analysit (Wella.) 

Furniflti'i Manual of Practical Assaying 

GrolenfelfB Principles of Modern Dairy Practice. IWoU.) 

Hdlloman'a TEit-book of Inorganic Chemistry. (Cooper.) 

• Oboi««oty Manual of Organic Chemistry. (Wallmr.) 

Jjuid««r'» Spectrum Atialysis, (Tingle.) 

Chemietry. (Tingle. ) , . . . , 

* HcfU)' and Larsen's Principles and Pndice of SuIter.mDking ... .6 
Mandel-s Handbook for Bio-chemical Lsboralory .I3i 

• Mardn'a Lsboratory Guide ID Qxxa.litatiuo Analysis with lie Blowpipe. . 121 
HaBon's Water-supply. (CoDsIdered Principally fiom a Sanltaty Sumdpolj 

3d Edlliun, Eewriltan S 

Examination of Water. (Chemical lUid BacterioiosicaL] izi 

Mfttlbew'B The Textile Fibres .8 

Uer«''E DetErmination of Radicles iu Caibon Compounds. (Tingle.), .lai 

Miller's Manual of Assaying 111 

Cyanide Process lai 

Uinet'e Production of Afuminum and its Industrial Uaa. (Waldo.) 121 

Mijter'a Elementary Teit-book of Chemistry. , , iii 

Morgan's An Outline of the Theory of Solutions and its Results iii 

Pinner's Introduction to Organic Che 
Poole's Calorific Power of Fi 
Prescott and Winslow's Elei 
ence to Sanitary W 
• Reisig'9 Guide to Piece-dyt 

MS of Wate 

Bucterlology, yrllh Special Refe 


odfroma Sanitary Slaudpoint, .Bi 
fln Inorganic Chemistry. IParl 

Assaying. .8v 

Tfon'meiallic Eli 
Ricketts and Miller's Holes on As 

Rideal'a Sewage and the Bacterial Purification of Sewage Bti 

Diainfeclion and the Preservation of Food. . Bio, 

Riggs'a Elemeni 

Ruddimao's tncompatibititlei In Piescrlptlons 

Eabin's Industrial and Artistic Technology of Paints and Varnish. . 
Salkowaki'a Phyaiologieal and Pathological Chemistrr, (Omdorif. 

ScIlimpC's Text-book of Volumetric Analysis. 

Essentials of Valumetric Analysic. 

• (JualitatiTB Chemical Analysis, , 

Smith's Lecture notes on Chemistry for Dental Students 

Stockbridge's Rocks and Soils. 

• Tilhnan's Elementary Lessons in Heat 

• DewripliTe General Chemistry 

Treadnrell'B Qualitatiye Analysis. (Hall.) 

Quantitative Analysis. tHalL) 

TuTDeaure and Russell's Public Water-supplies 

Van Devenler'B Physical Chemistry (or Beginneri. (Boltwood.) . . 

■WeMM'n Militurt EiplmivM. . , , ,8™. 

WeJueofennig'i AculTiis ■nd Softening of Boilsr Fecd-Watn , , ...Bvo, 

Welb'a Laboratory Guide in QviUJUtive Cbemical Aulj^B. Sto, 

Sbort CourH in Inorganic QiuliueiiB Chsmicil Analriis for EDgiiiMrine 

Teit-book of Cbtmlial Arithmetic jimo, 

Whipple's MicroKopF of Drinldng-wnter Svo, 

W.bon-B C;i>nide Proceises iimo, 

Chtotination Process iiiao, 

Winlon'i Microicopy of Vegetable Foods. Bvo, 

Wulling's ELemeiitary Course in InDrgaDic. Pharmaceutlcdi, and Medical 



■ Comitodt's Fiel 

.'French m 

■ra Engineerlne ar 
y for EngiaeeiB. . 

j and iMtnimsnte. 

3d Edition, Bewiitten , .Std, 

ady Refertnce Tahlea {Conversion Faclorsl. . 



lIs'B Problems in Survejioj 


of Surveying SmaU B. 

3tidEal'e Sewage and <be Bacterii 

Slebert and BieBin's Modern Sto 

Smith's Manual of Topographict 


8to half leather, 

line - - «i 

ilion of Sewage. 8? 

i and Masonry B. 

g. mc»v\iiu^.1 81 

• Trautwine's Civil EnELceer 
Venalile's OarbBge Cremalori 

lecturBl J 

opk i6mo.moro 

Law of Operations PieUn: 



Warren's Stereo tamT—Probl 



Uoent of Eiielimring InstrumectB. 
Wibon'i Topographic Surviylas Svo, 


BoUu'b PracticH] Trestise on tht CoDstrucIliiii of Icon Hi^hwa 

Bridges, ayo. 

Burr's Course on the Stresses in HridEes acd Hoof Trusses, Ar 

bed Bits, and 

ons 8to. 

Deaign and Construclion of Metallic Bridees 

Dn Bois's Mechenics of Engineering. VoL 11 

Foster's Treatise an Wooden Trestle Bridges 


Arches in Wood, Iron, ami Slone 


Howe's Treatise on Arches . 

Design of Simple Eoof-trusaes in Wood and SteeL . . . . . 


Symmetrical Masonry Arches 


Johnson, Bryan, and Tumeaure'a Theory and Practice In tb 

Designing ot 

. Small 4to, 

Merriman and Jacoby's Teil-book on Hoofs and BridBes: 

Part 1. Sf e?=-s in Simple Tnis-es. 

Pert H. C-t.,r)!l( Static?. ... . . , , 


«otIk)0*8 Memphis Bridge 

. . . 4fo. 

Waddell's De Pontibna, a Pocket-book for Bridge Ensmeers. 

•Speclfieationa for Steel Bridges 


»n Orifice. (Trautwine.) 8y 

Bov«y's Treatise on Hydraulics By 

Church's Mechanics of Engineering Sv 

DiaErams of Mean Velocity of Water in Open Channels pape 

Hydraulic Motors 8v 

Coffin's Graphical Solution of Hydraulic Problenra. i6mo, moroec- 

Plalher's Dynn mo meters, and the MeaBuiBineiil: ol ^tratt ii' 

ITolwtO's Walrr-supplf Engineering 

PuettcB't WaKr and PubUc Ueaim. 

Wnnr-flllrnlioii Works. , 

OanKuillel ■nd Kulwr's Gencml Formula for the Uniform Flo 
RiVin and Olher Ch«?DBl8, iHering and Truutwine. 

Haun'i Fillrmion ol PubUq Watcr-supplr. 

Hailthuni's Towers and Tanki for Waler-nprki. 

Conduits. . 

Hicdd'b WalFr-iupply. (Considered PiiDcipallj from a BaniUiy Standpc 

Witter-powet, aad DomeBtir Watet- 
RiVETS (Poit.,44C. addiUonal.) 


's TieatlH on Hydnulics. . . 

' M.cW.- 

ElementE at Analylical Uecb 


Reservoirs (or Irrigation, 

uppiy- ■ 

•• Thom 


"? Design and Construction of 

r-.i.pplr of the City of IT,* V 


laa Halen'a Hydraulic Tables. 


:riBl£ of Eagii 

Spalding-s Hydnaulic Cement 

Teit-book on Roads and Pavenwiits 

TBTl°r and Thompson's Treatise on Concrete. Plain and Reinfori 
Thurston's Materials of Engineering. 3 Parta 

Pari 1. Non-mFtallic Mati 

Part U Iian and Steel. . . 

Part III. A Treatise on 1 

Constituents J 

Thorstoa's Teil-book of Ibe Materials of Construction i 

TiUson's Street Pavements and Paving UateriaJs I 

Waddell'sDe Pontibus (A Pocket-book for Brid«e EnsiDeert.]. .lemo, a 

Specifications for Sleel Bridges la 

Wowl's (De V.) Treatise on the Resistance of Haleriala, and an Appendii 

and Other 

*ood'slDe V.) 1 

■Wood-S (M. P.) 

SteeL . . 

vation of Tin 


>k for Street Rallwfly Engineeis, .jijincl 

id Structures of American Railroads 

of Street Railroad Location , 161 

Bulfs CirU Engineer's Field-hook. , i6j 

CrandaU's Transition Curve ifii 

Railway and Other Earthwork Tahlea 

Dawson's "Engineering" and Electric Traction Pocket-book 161 

Drtdgo'sHistory of the Pennsylvflnia Railroad; (1879) 

* Drinker's Tunnelling. Explosive Compounds, and Rock Drills. 4 


<lodwln'E Raikoad Engineers' Field-boi 
Sovard's Transition Curre Field-book 
HudH>n-i Tables lor Calculating the C 

Holitorand Beard's Manual for Resident Engineers i6mo, 

nagles Field Manual for Railroad Eneineers i6ino, marocco, 

Philbrick's Field Manual for Engineers iCmo, morocco, 

SeecleB'B Field Engineering iftmo, morocco. 

Railroad Spiral. . , lOmo, morocco, 

Taytor-s Prismoidal Formulie and Earthwork. .- Bvo, 

'Irautwtges Method ot Calculating the Cube Contents of Eicavations and 

CooUdge anil Fr«nun-3 ElemcnU of GcniraJ Drafliag for Mccbanlea] Engl- 
ocr*- , .0bloDjC4to, 

Durtar'i KJnBiMtieB of Hacliinw. 

Eincb'i InlToductiaa to Proicctlie Geometry and its Applicationa 

Bill's Tail-boak on Shadei and Sludowa, and Fgnpcntivi- 

Junlsaa'i Elementa of UHbanlcal Drawing 

Advanced MrchanicaJ Drawing 8»o, 

Jones's Hactaiae Design: 

Part I. Kinematic! of Machinery Bii 

Part II, Foim, Strength, and Proportions of Parts 8»t 

HacCord's ElemeDts of Desciiptlre GeomcIrT' Bn 

Kinematice: or. Practical Hechanlsm. Svc 

MechanicBl Drawing 4lt 

Velocity Diagrams 8vi 

HicLeod's DescriptlTe Geometry Smell Svc 

• Uahin's Descriptive Geometry lod Stone-cutting Svc 

Hoyer's Descriptive Geometry Byi 

Reed's Topograptiical Drawing and Sketcliing .411: 

Teit-book 0.' Mechanical Drawing and ElemcnUry Uachioe Design. Svi: 

SchwamS and Menill-a Elements of Mechanism. 

Smith'} (R. S.J Manual of Topographical Drawing. (UcMIUan.) 

Smith lA. W. ) and Man's 1 'achine Design 

■ TilsWDTth's Elements of Mechanical Drawing. Obloni; 

Warren's Elements of Plane and Solid Free-hanil Geometrical Drawing . 1 
Drafting Initniments and Operations i 

Manual □[ Elementary Problems In the Linear PenpecCive of Form 

I. M.) Topographic Survey] 

/. T.l Free-hand Perspective 

imentHry Course in Deaciiptive Geomi 

: of TransQusaion. (Hermann 
B Art of Letter Engraving. .1: 


ly and Bracken's Teit-book of Physics 
ly's Lecture-notes on (he Tbeory of Elt 
Benjamin's Hislory of Elecliiclt; 

's Quantitative Chemical Analysis 

L" Crefiore and Squiei's Polarizing Pholo-chtDoogiaptv 

^^mwfoa'i "EngintuziaB" and Bluctrlc Trwtton poctoA-^ioQl»..i^™>.'' 



EDde.l iimo 

Duhem's TtiemiodyiiBaiics and Cbemistiy. (Burgees.) Svo 

4 Oo 
la 50 

1 s<y 

a SO. 

7 so 
1 so 


5 SO 
1 Sa 

J so 

fi 00 

3 00 

Gilbert's De Magnete. (Mottelay.l Bvo 

Hering-s Ready Refereuce Tables {CoaveiBion Factors) ifimo, morocco 

Landauer's Spectrum Analysis. (Tingle.). Svo 

LeChateliersHigh-temperatureMeasurements, (Boudouard— Buigeas.) lamo 
L'ib'E ElectrocbemisCry of Organic Compounds. <Loreni.f Svo 

• Michie's Elements of Wave Motion Relating to Sound and Light. Svo 

Hiaudefs Elementary Treatise on Electric Batteries. (Fishbach.) i3mo 

• ParshaU and Hobait' s Electric Machine Design 4I0. half morocco 

• Rosenberg's Electrical Engineering. (Haldane Gee— Kinibrunner.). . .Bvo 

Tory and Pitcher's Manual of Laboratory Physics SmaUBvo 

• LAW. 

• Treatise on the Milila^ Law* of DniteU Sts'tes. .' '..'....'..'..',. B.o 

• Sheep 




EocTClopedia of Founding and Dictionary of Foundry Terms Used In th 


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Control Large 8vo, 7 50 

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Thurston's Manual of Steam-boilers, their Designs, Construction and Opera- 
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<> <N 


nographs. Edil»d by MansfieW M 




S. Woodward . 

ry uf Uodcrn MathEm 

latica.byDflrid Eugene SmHb. 

Ho. I. Synt 

etic Projeclive Geome 

ry. by Geo 

go Bru 

c Halsled. 

Mo. 3- Beta 

minants. by Laenss 

Jifford W 

d. Ha. 

baUe Fund 

aas, by Jsmes HcMabaa. Ha. 

nic Func- 

tions, by W 

liam E. Bytriy. No. 

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by Edwsrd 

W. Hyde. «o. ?■ Pro 

wbility an 


by Botiert S 

cto. Analy 

tr Alfian. 

er Macfarlane, Ho. 

e. Differenlifll Equ 

atlons, by 

WiUlam W 

oteey Johnson. Ho. 


by MansfleU 

Merrimao. Ho. (i. F 

I Variable. 

by ThomBs 

. Eiskf , 


TTimaii's Hetb 



* and Jobnso 

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nd SpherEca 


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Abridged Ed. 8vi 

and Recipes. i ani< 

futal Engineerine. .......,- &^ 

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Hurley's Kinematics of Machines 

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Han's Car Lubrication 

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.Hntton's The Gas Engine. 

Jamison's Mechanical Drawing. 

Jodh's Machine Design; 

Part I. Kinematics of Machinery 

Pan II. Form, Strength, and Proportions of Parts , 

Ktnt's Mechanical Engineers' Pocket-book. . i6mo, 

.Ctn'a Power and Power Transmission. 

I«Dnatd-B Machine Shop, Tooh, and Methods 

*Lamu'i Modern Refrigerating Machinery. <.Po^,HB.'»n,an&^cw 

JfacCard'I Kinematics; or Practical Mechat^sm. 

KecbiinJcal Drawing. 

Piagramj ■ 

MucFuland'a SUnd&rd Reductioa Factors for Gatwa 



I so 

3 SO 

7 S* 

I so 

e Design. Svo 

RobioioD's PrinciplEt ol Mcchaniim 


fimith-B (0.1 Prisfl-working gl Mitala 


Thurslon'B TreatiM on Friction and L«H Work in HachiD 

err and Mill 

Anioul at a Machine and Prime Motor, and tbe Laws of EnerECticB. i zmo 


■Wolffs Windmill aa a Prime Mover. 

Kleln.), ,8vo 



Burr's Elasticity and Resiitance of the Uaterials of EngiaceriDC 

6lh Edition 

Maurer-B Technical Mechanics. 

Meiriman's Mechanics of Materials ■ 



Sabiii's iDdustrial and Artistic Techooloey of Paints and Varnish. Svo 

.3 vols.. Svo 

Part III, A Treatise on Brasses, Bronzes, and Other Alloys and their 

Wood's <De V.) Treatise oti the Resistance of Uateriala and.aii 

Appeodi. on 

Wood's IM. P ; Rustless CoallnEs: Carrosion and ElectrolfBi 

of Iron and 


Cainofa Reflections on the Motive Power of Heat (Thurston, 
DawsoaS ■'ineineering" and Electric ttUKtion Pocket-book. . 

,i6mo" mor. 


KoEasB's PrBctice anil Theory of the Injector. . 

MacCord's Slide-yaWes, 

Meier's Modem Locomotive Construetion 

Peibodya Manual of the SICBm-oneise Indical 
Tables of tbo Propectlea of Ealuratcd Stea 
Thetmodytiamics ot the Steam-engine ant 

Pupin's Thermodynamies ol ReverBible Cyclee In Gases and Saturated V 

(OsterberB.l. . - 

Reagan's Locomotives: Simple Compound, and Electric 

Eor.tBen's Principles of Thermodynamics. (Du'Bois,) 

^Snclair's Locomotive Engine Running and Uanageinenl 

Smart's Handbook of Engineering Laboratory Practico, 

Snow's Steam-boiler Practice 

Spaueler's Valve-gears. 

Notes on Theimodynamlcs 

Spancler, Greene, and Uarsliali*s Elementa of Stedm-fln£ineeriog 

Thurston's Handy Tables 

Manual of the Steam-engine a vols 

Part I. History, Structure, and Theory Byo, 

Partn. Design, CoostnictioQ, and Operation. 

Handbooli of Engine and Boiler TilalB. and the Use of the Indlcat 

the Prony Brake 

Stationary Steam-engines 

Steam-boiler Explosions in Theory and in Practice 

VaDual of Steam-boilers, their Designe, Constcuclion, and Operation, . . 

'Wehrenfenning's Analysis and Softening of Boiler Feed-Water (Patterson 

"WeiBhach's Heal, Steam, and Steam-engines, (Du Bois.) 

Whitham's Steam-engine Design 

Wood's Thermodynamics, Heat Motors, and Refcigerating Machines. 


Barr's Kinematics of Machinery 

* Bovey's SIrenglti of Materials and Theory at 
Chase's The Art of Pattern- making 

Motes and Eiamples in Mechanics 

Compton's First Lessons in HeUl-working. is 

Compton and De Groodfs The Speed Lathe u 

Cromwell's Treatii* on Toothed Gearing 13 

Treatise on Belts and Pulleys ij 

Dani'sTeit-hooliof Elementary Mechanics for Co lieges and Schools, i: 

Dingey's Machinery Pattern Making Ij 

Dredge's Record of the Transportation Eihiblls Building of the Woi 

Columbian Exposition of iSgs. . 4to half more 

u Bois'B Elementary Principles ot MechanlcB- 

VoL I. Kinematics. , 

VoL U. Statics 

Mechanics of Engineering, Vol. L ,^™a 

Vol. n. •^™ 

Dnjiej'v Kinematics of UAchinea. . ..,., ., --■ 


Flttftnld** BotWD MacbioiiL 

Ftother'i PrnunoQuIciit and the Uea*iir£ment of Power. , . . .,.,..., 

Rope DcWlns _ 

&«■'■ LocamoUvc Spaiki. 

■ Grtent'i Suuclunl Hectucicc , 

H»IP» Cat Lubtkallon 

HoUy'm Alt o! Saw Filing 

Jamo'iKinematlciot aPoInlind Ibe Rstioiui Ueciumicsof a Pailicle. 

• Johnson's <W. W.) Theoraticsl Mechanics 

j6lin«oii'» 'L. J. ) Stnlics by Crupliid and Algabrale Methnds 

Jjno'i Machine Dcilgn: 

Pari I. Kiaeoiaiici of MatUoety Bvo, 

Pari II. Form, Streneth, and Proportions of Parts. . . S\ 

K«t'> Power and Power Transmission. 8\ 

Lanza's Applied Mechanics. -.,--.,,.-.-----,,--,,,-. Si 

Leonard'i Machine Shop. Tools, and Methods 8t 

■ Lore nz's Modern RelriieratlnK Uacbinery. (Pgpe, Haven, and DeBD.).Sv 
HacCord's Kiaematics ; or- Practical Uechaniam. ................... ,S\ 

Velocity Diagrami St 

•Martin's Text Book oo Moehanlea, VoL 1, Statics. iim 

Maurer'n Technical Mechanics. 81 

Merrimon'G Mechanics of Btaterlals. -..-.- , , .flvD. 

• Ekmenls of Mechanics. im 

• Michie'B Elements ol Analytical Mechanics S< 

•Potshall and Hobart'9 Electric MflchinnDeaiEn., 4to, half moroc 

ReBtmi'a Locomollves Simple, Compound, and Electric lan 

Raid's Course in Mechanical Drawing Si 

Tetl-book of Hectuinicol Drawine and Elementaiy M wrhlni . Design. 81 

Rkbards'a Compressed Air. no 

Robinson's Prioclplei of UccliBniaDi S< 

Ryan. Jlorris. and Hoiie's Eiectrieal Machinery. Vol. I Bi 

Sanborn's Mechanics: Problems ....Large 13m 

Schwamb and Merrill's Elements of Mechanism 81 

Snulh'«(0,)Pie9a-workineofMrUl6 8vo, 

Smith's (A. W.)Mflleriala of Mathioea 

Smith (A. W.) and Man's Machine Design 

Spaogler, Greene, and Marshall's ElemCDts of Steam-engineerinff. ■ - -., , 

Animal BE a Machine and Prime Motor, and the LawE al Energetici. 

Warren's ElemeDlsoiMacbineConilruction and Drawlnn 

Wfisbach'sKinemalicsand Power of Transmission. (Herrmann— Klein. 

Machinery of Transmission and Governars. (Herrmann— Klein. 
Wood's Elements of Analylical Mechanics 

Ftlnclples of Elementary Mechanics 


Tho World's Columbian Exposition of 1853 


Egleston's MetallurgT of Silver, Gold, Bad Mercury- 

Vol. I. Silver. 

Vol. II. Gold and Mercury 

Goesel'B Minerals and Helals; A Reference Book ifinio 

•- Iles's teBd-Hmaltiog. (Postage 9 cenW ^.Mi^\DnttV.^ 

Keep's Cast Iron 


Kunhardt's Practice of Ore Dressing in Europe 8vo, 

Le Chatelier's High-temperature Measurements. (Boudouard — Burgess. )i2mo. 

Metcalf' s Steel. A Manual for Steel-users i2mo, 

Miller's Cyanide Process i2mo, 

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