Transcriber’s Notes:
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in the original text. Equal signs “=” before and after a word or
phrase indicate =bold= in the original text. Small capitals have been
converted to SOLID capitals. Footnotes have been moved so they do not
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A NEW SYSTEM OF
CHEMICAL PHILOSOPHY.
PART FIRST.--VOL. II.
REPRODUCED IN FACSIMILIE
BY
WILLIAM DAWSON & SONS LTD.
102 WIGMORE STREET,
LONDON, W.1
AND PRINTED BY
HENDERSON & SPALDING
SYLVAN GROVE, OLD KENT ROAD,
LONDON, S.E.15
THIS EDITION IS LIMITED TO 1,000 COPIES
A NEW SYSTEM OF
CHEMICAL PHILOSOPHY.
_PART FIRST_
OF
VOL. II.
BY
JOHN DALTON, F.R.S.
President of the Literary and Philosophical Society, Manchester.
Corresponding Member of the Royal Academy of Sciences, Paris,
Member of the Royal Academy, Munich, and of the Cæsarean
Natural History Society, Moscow;
Honorary Member of the Royal Medical Society, Edinburgh,
and of the Philosophical Societies of Bristol, Cambridge,
Leeds, Sheffield and Yorkshire.
Manchester:
Printed by the Executors of S. Russell.
FOR
GEORGE WILSON, ESSEX STREET, STRAND
_LONDON_.
1827.
TO
JOHN SHARPE, ESQ. F. R. S.
OF STANMORE, MIDDLESEX,
(_Late of Manchester_,)
AS A TESTIMONY OF HIS FRIENDLY REGARD, AND OF HIS
LIBERAL ENCOURAGEMENT GIVEN TO THE PROMOTION
OF CHEMICAL SCIENCE:
AND TO
PETER EWART, ESQ.
_Vice-President of the Literary and Philosophical Society
of Manchester_,
ON THE SCORE OF FRIENDSHIP,
BUT MORE ESPECIALLY FOR THE ABLE EXPOSITION AND
EXCELLENT ILLUSTRATIONS OF THE FUNDAMENTAL
PRINCIPLES OF MECHANICS,
IN HIS ESSAY ON THE MEASURE OF MOVING FORCE,[1]
THIS WORK IS RESPECTFULLY INSCRIBED BY
_THE AUTHOR_.
[Footnote 1: Manchester Memoirs, Vol. II. (_second series._)]
PREFACE.
The work now submitted to the public was begun to be printed in 1817;
and the 13th and 14th sections, containing the oxides and sulphurets,
were printed off before the end of October of the same year. The
printing of the rest of the work to the appendix was finished in
September, 1821. One sheet of the appendix was printed at the end of
1823; but no addition was afterwards made till May, 1826; when the
printing was resumed, and has been continued to the present time.
It may be asked, what were the motives for such a plan of procedure.
To this it may be replied, that soon after the publication of the
first volume (in 1810), I began to prepare materials, and to institute
experiments, relating to the oxides, &c., with occasional diversions
into other departments of chemistry, as circumstances arose. As a great
portion of my time was always necessarily engaged in professional
duties, and as that part of the work I was about to commence was one
running into detail, I thought it would be best to print it as I
proceeded, whilst the train of thought and of experiments was fresh in
view. The advantage in this case was expected to be partly at least
counterbalanced by the loss of discoveries and improvements likely
to be made in the interval between the printing and publishing of
the several articles. This I was aware of; but as a principal object
I had in view was to give the results of my own experience, in the
various departments of chemical science, rather than to form the best
compilation of Chemistry at the period, this object was most likely to
be obtained by the proposed plan. It is true the time the work has been
in the press has far exceeded my expectation; notwithstanding this I am
not conscious of any very material alterations or additions, which I
should wish to make at the present moment.
It affords me great pleasure to acknowledge the assistance I have
had during the progress of this volume, from a valuable selection of
chemical apparatus, for which I am indebted to the generosity of Mr.
Sharpe; also the continued and friendly intercourse with Dr. Henry,
whose discussions on scientific subjects are always instructive, and
whose stores are always open when the promotion of science is the
object.
My present design is to add a second part to this volume, and with that
to finish the work. It will consist of the more complex compounds.
Acids, and other products of the vegetable kingdom, Salts, &c., will
form principal parts. Already I have a stock of experiments on these
subjects; but I am not satisfied without exploring this region afresh.
_August, 1827._
CONTENTS OF VOL. II.
_Part First._
Page.
CHAP. V.--COMPOUNDS OF TWO ELEMENTS.
SECTION 13. _Metallic Oxides_ 1
_Oxide of Gold_ 5
---- _Platina_ 11
---- _Silver_ 17
_Oxides of Mercury_ 19
_Oxide of Palladium_ 24
_Oxides of Rhodium, Iridium, and Osmium_ 26
---- _Copper_ 26
---- _Iron_ 28
---- _Nickel_ 34
---- _Tin_ 36
---- _Lead_ 39
_Oxide of Zinc_ 51
_Oxides of Potassium_ 53
---- _Sodium_ 56
_Oxide of Bismuth_ 57
_Oxides of Antimony_ 58
_Oxide of Tellurium_ 62
_Oxides of Arsenic_ 63
---- _Cobalt_ 68
---- _Manganese_ 71
---- _Chromium_ 80
---- _Uranium_ 86
---- _Molybdenum_ 87
---- _Tungsten_ 90
---- _Titanium_ 91
---- _Columbium_ 92
---- _Cerium_ 94
SECTION 14. _Earthy, Alkaline,
and Metallic Sulphurets_ 96
_Sulphurets of Lime_ 99
_Sulphuret of Magnesia_ 111
_Sulphurets of Barytes_ 112
---- _Strontites_ 114
---- _Alumine, Silex, Yttria,
Glucine and Zircone_ 114
---- _Potash_ 116
---- _Soda_ 119
_Sulphuret of Ammonia_ 120
_Sulphurets of Gold_ 121
_Sulphuret of Platina_ 123
_Sulphurets of Silver_ 126
---- _Mercury_ 127
_Sulphuret of Palladium_ 131
---- _Rhodium_ 132
---- _Iridium_ 132
---- _Osmium_ 132
_Sulphurets of Copper_ 133
---- _Iron_ 134
---- _Nickel_ 138
---- _Tin_ 139
---- _Lead_ 144
---- _Zinc_ 146
---- _Potassium and Sodium_ 148
---- _Bismuth_ 149
---- _Antimony_ 151
_Sulphuret of Tellurium_ 153
_Sulphurets of Arsenic_ 153
_Sulphuret of Cobalt_ 160
_Sulphurets of Manganese_ 162
_Sulphuret of Chromium_ 163
---- _Uranium_ 164
---- _Molybdenum_ 164
_Sulphuret of Tungsten_ 164
_Sulphurets of Titanium, Columbium,
and Cerium_ 165
SECTION 15. _Earthy, Alkaline,
and Metallic Phosphurets_ 166
_Phosphuret of Hydrogen_ 169
_Phosphurets of Carbon and Sulphur_ 184
_Phosphuret of Lime_ 184
---- _Barytes_ 188
---- _Strontites_ 190
---- _Gold_ 191
---- _Platina_ 194
---- _Silver_ 195
---- _Mercury_ 197
---- _Palladium_ 198
---- _Copper_ 199
---- _Iron_ 201
---- _Nickel_ 201
---- _Tin_ 202
---- _Lead_ 203
_Phosphurets of Zinc and Potassium_ 204
---- _Sodium and Bismuth_ 207
---- _Antimony and Arsenic_ 208
_Phosphuret of Cobalt_ 209
---- _Manganese_ 210
SECTION 16. _Carburets_ 211
---- of _Iron ... steel_ 212-214
SECTION 17. _Metallic Alloys_ 218
_Alloys of Gold, with other metals_ 222
---- _Platina, with other metals_ 226
---- _Silver, with other metals_ 228
---- _Mercury, and other metals:
amalgams_ 230
_Triple, Quadruple, &c. amalgams_ 236
_Alloys of Copper, with other metals_ 238
---- _Iron, with other metals_ 253
_Alloys of Nickel and Tin, with do._ 254
---- _Lead, with do._ 258
_Triple Alloys, Solders; fusible metal, &c._ 263
APPENDIX.
_Abstract of De la Roche and Berard’s essay
on the specific heat of gases_ 268
---- _Dulong and Petit’s essays,
On the expansion of air, mercury,
glass, iron, copper, and platina,
by heat_ 272
_On the capacities of certain bodies,
for heat_ 274
_On the laws of refrigeration_ 277
_On the specific heats of certain
bodies_ 280
_Remarks on the above essays_ 282
_New Table of the forces of vapours_ 298
_Table of the expansion of air, and the force
of aqueous and ætherial vapour, adapted
to atmospheric temperatures_ 299
_Applications of the above table_ 300
_Formulæ for determining the proportions of
combustible gases, in mixtures_ 305
_Heat produced by the combustion of gases_ 309
_Absorption of gases by water_ 309
_Fluoric acid--deutoxide of hydrogen_ 311
_Muriatic acid--oxymuriatic acid_ 313
_Nitric acid--compounds of azote and oxygen_ 315
_On ammonia_ 328
_Decomposition of ammonia by nitrous oxide_ 330
---- ---- ---- _by nitrous gas and oxygen_ 332
_Volume of gases from the decomposition of
ammonia_ 335
_Decomposition of ammonia by a red heat_ 335
_Decomposition of ammonia by oxymuriatic acid_335
_Sulphuret of Carbon_ 338
_Potassium, Sodium, &c._ 340
_Alum_ 341
_New table of the relative weights of atoms._ 352
ADDENDA. _Steel; mixed gases;
expansion of liquids by heat_ 354
NEW SYSTEM OF _CHEMICAL PHILOSOPHY_.
CHAP. V.
SECTION 13.
METALLIC OXIDES.
All the metals are disposed to combine with oxygen, but the combination
is effected more easily with some than with others; the compound is
usually called an _oxide_, but in some instances it is also called an
_acid_. The same metal combines with one, two, or perhaps more atoms of
oxygen, forming compounds which may be distinguished according to Dr.
Thomson, by the terms _protoxide_, _deutoxide_, _tritoxide_, &c.
Such however is the repulsion of oxygen to oxygen that we rarely
find three atoms of it retained by a single atom of any kind; and
there are not many instances of metals capable of holding two atoms
of oxygen. Various modifications of the proportions of metals and
oxygen arise from the combinations of the oxides themselves one with
another and with oxygen, so as to lead some to imagine that an atom of
metal in some instances combines with 3, 4, or more of oxygen. This
is altogether improbable: It is much more simple to suppose that one
atom of oxygen connects two or more atoms of protoxide, 1 of protoxide
unites to 1 or more of deutoxide, &c. These intermediate oxides are in
few if any instances found to combine with acids like the other two
oxides.
There is no reason that I am acquainted with for disbelieving that
oxygen combined with a metal is still repulsive of oxygen, and that by
the same law as particles of an elastic fluid; that is, the repulsion
is inversely as the distance of the centres of the atoms. Hence it
may be demonstrated that it requires twice the strength of affinity
to form a deutoxide as a protoxide, three times the strength to
form a tritoxide as a protoxide, &c. On this account it is, in all
probability, that deutoxides are not numerous, and tritoxides are
rarely if ever found.
The quantity of oxygen that combines with any metal to form an oxide
may be investigated by several methods.
1st. By combustion; a given weight of the metal may be burned and the
oxide produced may be collected and weighed; when the increase by
combustion will appear.
2. By solution in an acid and precipitation by an earth or alkali; in
this case a given weight of the metal is dissolved and precipitated;
the precipitate collected and sufficiently dried shews the increase by
oxygen.
3. By transferring the oxygen from an oxide to another metal; in this
case the metal in question is usually immersed in a saline solution of
the other metal; this latter metal gives up its oxygen to the former
and is itself reformed or _revived_ as it is termed.
4. By determining the proportion of hydrogen gas evolved during the
solution of a given weight of metal; then allowing half of that volume
for its equivalent of oxygenous gas, the weight of it shews the oxygen
united to the metal; it being now well understood that water furnishes
the two elements of hydrogen and oxygen in such case.
5. The higher oxides are conveniently determined by the application of
the solution of oxymuriate of lime to the lower oxides in solution.
6. The quantity of oxygen in several oxides may be found from the
quantity of nitrous gas evolved during the solution of a given weight
of metal in nitric acid.
The first four methods have been used by chemists for several years
past; the two last I have added from my own experience, having found
them very useful assistants in various instances. The last method by
nitrous gas, has indeed been proposed before, and labour bestowed on
it both by others and myself, but without reducing the results to any
certainty, till lately; the principal cause of this want of success
has arisen from misunderstanding the nature and constitution of nitric
acid. Most chemists seem with me to have mistaken _nitrous_ acid for
_nitric_; the former is composed of 1 atom of azote and 2 of oxygen; or
perhaps of 2 azote and 4 oxygen; the latter of 2 azote and 5 oxygen,
or 2 nitrous gas and 3 oxygen; the weight of the former is 19, or its
double 38, on my scale, and that of the latter 45. [My reasons for
adopting the above conclusion respecting nitrous acid, which is at
variance with that in VOL. 1, p. 331, will be given hereafter.] When
therefore a metal is oxidized by nitric acid, 3 atoms of oxygen (= 21)
go to the metal, and 2 atoms of nitrous gas (= 24) are disengaged.
Hence ⅞ of the weight of nitrous gas evolved is the weight of oxygen
combined. It sometimes happens however that the nitrous gas is partly
or wholly retained by the residue of nitric acid; but in this case
the oxymuriate of lime can be applied to convert the nitrous gas into
nitric acid, and from the oxygen imbibed the quantity of nitrous gas
may be inferred.
1. _Oxide of Gold._
Some difficulties have been found in ascertaining both the number and
proportions of the oxides of gold; hence the differences in the results
of authors.
Gold does not burn by exposure to heat, but gold leaf and gold wire
may be deflagrated by electricity and galvanism; a purple powder is
the product, which is considered by some as the protoxide of gold; but
others, after Macquer and Proust, conceive with greater probability
that this powder is nothing but gold reduced to its ultimate division.
Solutions of gold which are of a fine yellow, give a purple stain; and
gold deoxidized by green sulphate of iron is precipitated blue, which
precipitate gradually assumes a yellow colour as the particles become
united. The very weak affinity of gold for oxygen is shewn by the
difficulty with which it is oxidized and the ease with which the oxygen
is expelled again by heat; these facts seem to preclude the idea of
gold combining with oxygen in high temperatures.
_Protoxide._ Gold is scarcely affected by pure sulphuric, nitric
or muriatic acid; but it is easily oxidized and dissolved by
nitro-muriatic acid (that is, a mixture of nitric and muriatic acids)
when assisted by a temperature of 150 or 200°. Caustic potash being put
into the solution and heated, a brownish black precipitate is obtained;
but a part of the oxide remains in solution combined with the muriate
of potash, according to Vauquelin; and Proust has observed that the
oxide cannot be washed and dried in a moderate heat without a portion
of the gold being revived; hence the difficulty of ascertaining in this
way the weight of oxygen combining with gold.
I have succeeded, as I apprehend, in determining the relative weights
of gold and oxygen, by two methods, which mutually corroborate each
other. The first is by means of the nitrous gas generated by the
solution of gold; and the second is, by finding what quantity of green
oxide of iron is converted into red by precipitating a given weight of
gold in solution.
Ten grains of guinea gold of the sp. gr. 17.3, were repeatedly
dissolved in a small excess of nitro-muriatic acid; the quantity and
purity of the nitrous gas generated were duly observed and allowance
made for the loss occasioned by a small portion of common air
originally in the gas bottle. The volume of nitrous gas corrected as
above was always found between 1100 and 1200 grain measures, the weight
of which may be estimated at 1.6 grains, corresponding to 1.4 grains of
oxygen. The small portion of alloy (¹/₁₂) known to be in standard gold
is chiefly copper with a small part silver; now it will be seen in the
sequel that copper takes ¼ of its weight of oxygen; hence if we allow
.8 of a grain for copper and .2 for the oxygen combining with it, we
shall have 9.2 gold united to 1.2 oxygen, or 100 gold with 13 oxygen,
which is nearly the same as Berzelius has determined by precipitating
the gold by mercury.--Again, 10 grains of gold were dissolved as above
(= 9.2 pure) and precipitated by a solution of pure green sulphate of
iron of the sp. gr. 1.181 and which I had previously proved to contain
9 grains of green oxide in 100 measures. They converted 120 measures
of this green sulphate into yellow, which was carefully precipitated
afterwards by lime water, dried and weighed. The gold precipitated was
found very nearly 9 grains; and the yellow oxide of iron mixed with
oxide of copper was nearly 13 grains. Now 120 measures sulphate iron
contain 10.8 grains green oxide, and these require ¹/₉ of their weight
of oxygen (see the oxides of iron) to be changed into yellow oxide, or
1.2 oxygen. Hence it appears that the oxygen combined with the gold was
transferred to the iron unchanged in quantity. It is to be observed
however that green oxide of iron not only deoxidates the gold but it
semideoxidates the copper also; so that .1 of the transferred oxygen
above might be said to be derived from the copper, and the rest, or 1.1
from the 9 grains of gold; this would give 100 gold to 12.2 oxygen,
which is still nearer to the determination of Berzelius. Upon the whole
I am inclined to adopt the proportion of 8 to 1 or 100 to 12.5 as that
which appears the most correct approximation and at the same time a
ratio easily remembered and adapted to facilitate calculations.
We are now to consider whether the above is the protoxide. As no other
oxide has been clearly shewn to exist, and as this combines with
muriatic acid, with ammonia, with the oxide of tin, &c. and is wholly
deoxidated by green sulphate of iron and by a moderate heat, there
seems every reason to conclude it is a combination of the most simple
kind, or 1 atom of metal to 1 of oxygen. Hence the atom of oxygen being
7, that of gold must be 56, and not 140 or 200, as stated VOL. 1, p.
250.
Berzelius seems to consider the above as the tritoxide, or three atoms
of oxygen to one of gold; but it is extremely improbable that gold,
which is allowed to have a weak affinity for oxygen, should be able to
restrain the violent repulsion of three atoms of oxygen, and should on
every occasion lose them all at once, and not by degrees, as is usual
with other high oxides.
Subjoined are the results of various authors in regard to the oxide of
gold, but generally given with diffidence as to their accuracy.
gold oxygen
Bergman 100 + 10
Proust -- + 8.57 to 31.
Oberkampf -- + 10
Berzelius -- + 12 (4 suboxide)
My results -- + 12.5
Since writing the above I have had an opportunity of repeating the
experiments on the oxide of gold by an improved nitrous gas apparatus,
calculated almost entirely to exclude atmospheric air; I find less
nitrous gas produced during the solution than stated above, sometimes
by ⅓, and that it is variable according to the excess of nitric acid;
also that the solution requires a portion of oxymuriatic acid as an
equivalent for the nitrous gas retained. I prefer, however, the method
of oxidizing the green sulphate of iron; by putting a small excess of
the green sulphate and precipitating, first the red oxide and then the
green, I obtained very distinct results. On the whole I am inclined to
think my results preceding these have rather overrated the oxygen, and
that it would as nearly be stated at 11 on the hundred. This would be
nearly a mean of those in the above table, and would require the atom
of gold to be 63, and that of the oxide 70. Between the two extremes of
56 and 63 it is most probable the true weight of the atom of gold will
be found.
It may be proper to add that I have found 100 grain measures of
muriatic acid (1.16), and 25 of nitric (1.35), are sufficient to
dissolve 40 grains of standard gold; and I have reason to think the
acids are in due proportion nearly, though different from what is
usually recommended and employed.
2. _Oxide of Platina._
Platina exhibits greater difficulties than gold in the investigation
of its compounds with oxygen. It is not oxidized by heat; but by the
explosion of an electric battery it is converted into a black powder,
which is most probably the metal in extreme division, though it has
been considered by some as the protoxide. Platina is capable of being
oxidized and dissolved by nitro-muriatic acid, but less easily than
gold; it requires more acid, as high or higher temperature and long
continued digestion; nitrous gas is given out, during the solution,
but sparingly. When lime or an alkali is added to the solution with
a view to precipitate the oxide, a triple compound is usually formed
of the acid, the oxide and the alkali, which is in most instances
precipitated. This weighty compound renders the valuation of the oxygen
in it very uncertain.
Chenevix has made some observations on the oxides of platina, (see
Nichols. Journ. 7. p. 178.) He finds two oxides: the one consists of
93 platina and 7 oxygen; the other of 87 platina and 13 oxygen; but
the experiments on which these results rest are not quite satisfactory.
Mr. E. Davy in the 40th vol. of the Philos. Magazine, states his having
reduced the oxide of platina in solution by means of hydrogen; and
that he finds the oxide to consist of 84 platina and 16 oxygen nearly.
I could not succeed at all in effecting the reduction of the metal in
this way.
Berzelius has lately given us the results of his investigation on this
subject. (An. de Chimie 87--126.) According to this distinguished
chemist there are two oxides of platina; the first consists of 100
metal and 8¼ oxygen, and the second of 100 metal and 16½ oxygen,
nearly. In order to understand his process it may be proper to premise
that when nitro-muriatic acid has dissolved as much platina as it can,
there is still a great excess of one or both of the acids, which is
unnecessary for the existence of the solution, and which may, and in
general ought to be expelled by evaporation; by exposing the solution
to a heat of 100 or 150° the excess of both acids is in great part
driven off and a dry red mass is obtained, without smell, but very
deliquescent. It is equal to or rather more than twice the weight of
the platina. It consists of water, muriatic and nitric acids, oxygen
and platina; it is still an acid salt. By exposing the dry mass again
to a heat of 400 or 500°, it liquifies, exhales acid fumes having
the odour of oxymuriatic acid, and becomes again a dry mass of an
olive colour, exhaling fumes as the heat increases, and loses about
¼ of its weight. It is still soluble in water, except a few atoms of
black powder, continues acid to the tests, and may be considered as a
supermuriate of platina. If this olive powder be again heated almost to
red, it exhales a visible smoke in the open air, which has the smell
of oxymuriatic acid, and becomes a light brown powder, having lost a
little weight. It is then neither deliquescent nor soluble in water
except in a small degree so as to give the yellow colour. In this state
it has been considered as a neutral muriate. By a moderately bright red
heat this powder is decomposed and leaves a black spongy mass which is
found to be pure platina.
The insoluble muriate of platina according to Mr. E. Davy, contains
72.5 per cent. of platina, and Berzelius finds 73.3; the loss is
considered as oxymuriatic acid; hence from the known proportions of
this acid Berzelius infers the constituents of 100 muriate = 73.3
platina, 6.075 oxygen and 20.625 muriatic acid; or 100 platina take
8.3 oxygen. The near agreement of the above authors is favourable to
the accuracy of their results; but I have found some difficulty in
obtaining the insoluble muriate free from the soluble one, and at the
same time from reduced platina because the precise degree of heat
requisite to produce it is neither well known nor easily attained; and
it is desirable that a certain weight of platina should be dissolved
and the same weight reproduced as a confirmation of accuracy. From a
train of experiments on the soluble and insoluble muriates of platina,
the salts being obtained from the purified laminated metal, I am
disposed to consider the above results as good approximations to the
truth.
In order to obtain the other oxide, Berzelius digests mercury in a
solution of the supermuriate of platina; a black powder is thrown down,
which is found to be platina, and mercury is taken up, being oxidized
at the expence of the platina. It was found that 16.7 grains of mercury
had precipitated 8.5 of platina; and the mercury being calculated as
in the state of deutoxide, contained, from the known proportions of
this metal, 1.4 oxygen; hence 8.5 platina must have yielded 1.4 oxygen;
and if 8.5 ∶ 1.4 ∷ 100 ∶ 16.4; so that 100 platina must have had
16.4 oxygen in the supermuriate, or twice the quantity it had in the
insoluble muriate.
This conclusion appears to me premature; the mercurial oxide should at
least have been precipitated and a corresponding quantity have been
found and proved to be the red oxide. Even had this been the case,
it is not easy to determine what quantity of it might be due to the
residue of nitro-muriatic acid. But I have not found that the common
yellow or red oxide of mercury is precipitated by lime water in such
case; the precipitate is brown, and evidently contains both mercury and
platina. Proust had found in his excellent essay on platina (Journ. de
Physique 52--437, 1801) that mercury decomposes muriate of platina,
that an amalgam of platina with a little calomel, and much mercury
in powder, were precipitated; exposed to heat, a fine black powder
was left which had the characters of platina. Into a solution of pure
platina that had been evaporated to dryness in 150° and redissolved,
I put 9¼ grs. of mercury, and boiled it for 10 minutes in a glass
capsule, till there was apparently no further change; the liquor
filtered was as yellow as at first; the mixture of black powder and
running mercury remaining on the filter, when dried, weighed 6½ grains;
this heated to a low red in an iron spoon, left 1 grain of fine black
powder; the liquid saturated with lime water, yielded 2½ grains dry
black powder insoluble in cold nitric acid; after this, protomuriate of
tin threw down 5¾ grains of the compound oxides of platina and tin. The
solution at first contained 3.3 grains of platina.
In another experiment 2 parts of calomel were put to 1 of platina in
solution; when heated to boiling, the calomel was dissolved and a
little black powder was precipitated, which did not amount to half
the weight of the platina. Lime water threw down from the liquid,
a yellowish olive or brown precipitate, partially soluble in cold
nitro-muriatic acid; and after this, muriate of tin yielded a brown
precipitate. These experiments shew that the action between muriate of
platina and mercury or the mercurial salts, is of a complicated nature,
and is not limited to the decomposition of the oxide of platina and the
substitution of the deutoxide of mercury in its place.
The difficulties abovementioned have led me to investigate the oxygen
combining with platina by means of the nitrous gas yielded upon its
solution in nitro-muriatic acid. By three distinct experiments I found
that 10 grains of pure platina by solution yielded nearly 750 grain
measures of nitrous gas, which may be considered as 1 grain in weight;
⅞ of which = .875 for oxygen; this would give 8.75 oxygen per cent. But
from a subsequent experiment made under circumstances calculated to
preclude as much as possible every source of fallacy, I obtained 790
measures of nitrous gas from 10 grains of platina; and the solution
afterwards took 60 measures of oxymuriatic acid gas before a permanent
smell of the gas was produced. These 790 measures = 1.05 grain, ⅞
of which = .92, to which add .04 for the oxygen acquired from the
oxymuriatic acid, and we have .96 oxygen for 10 platina; or 100 platina
take 9.6 oxygen. But if 9.6 ∶ 100 ∷ 7 ∶ 73, for the weight of an atom
of platina, and 80 for that of the protoxide, as I apprehend it to be,
and the only oxide of platina we can at present form. (The atom of
platina in Vol. 1, page 248, was estimated at 100.)
3. _Oxide of Silver._
When silver wire is exploded by electricity in oxygen gas, a black
powder is produced, which is the oxide of silver. If silver be
dissolved in nitric acid and precipitated by lime water, an olive
brown powder falls which becomes black when exposed to the light. This
black powder is the only oxide of silver with which we are acquainted.
The proportion of silver and oxygen has been investigated by various
chemists; the results are as under.
silver oxygen
Wenzel 100 + 8.5
Proust + 9.5
Bucholz and Rose + 9.5[2]
Gay Lussac + 7.6[3]
Berzelius + 7.925
[Footnote 2: 7.9 when duly corrected. Annal. de Chimie, 78--114.]
[Footnote 3: Memoirs d’Arcueil 2--168.]
From the solution of 170 grains of standard silver I obtained nearly 30
oz. measures of nitrous gas = 18½ grains, corresponding to 16 oxygen.
This would give 9.4 oxygen upon 100 silver. But as ⅒ of the metal or 17
grains was copper, and this takes ¼ of its weight of oxygen, we shall
have 159 silver and 11¾ oxygen, or 100 silver and 7.7 oxygen nearly.
If we adopt 7.8 as the proper quantity of oxygen on 100 silver, we
shall have 7.8 ∶ 100 ∷ 7 ∶ 90 nearly, which represents the weight of an
atom of silver, and 97 that of the oxide.
4. _Oxides of Mercury._
Two oxides of mercury have been long known and are well distinguished
from each other. They may be obtained by exposing mercury to a heat not
exceeding 600°, in contact with oxygen gas or atmospheric air, and due
agitation; but this method is rarely adopted in practice. A high degree
of heat decomposes the oxides again.
_Protoxide._ To obtain the protoxide, mercury must be slowly dissolved
in dilute nitric acid without heat, and an excess of mercury must be
used. If to 1000 grain measures of nitric acid, 1.2 sp. gr. be put 500
grains of mercury, by occasional agitation the requisite solution will
be obtained in 24 hours. A portion of this solution must be treated
with a small excess of lime water or caustic alkali, when a black
powder will be thrown down, which is the oxide containing a minimum of
oxygen, and hence may be considered the protoxide.
_Deutoxide._ If to 1000 measures of nitric acid, 1.2 sp. gr. be put
350 grains of mercury, and the mixture be boiled till the mercury
disappear, a solution will be obtained containing the deutoxide. A
portion of this being treated as beforementioned with lime water, a
yellowish red powder is precipitated, which is the oxide of mercury
containing a maximum of oxygen; all the later authors agree that it
contains just double the quantity of oxygen to a given portion of
mercury that the former does, and may therefore be called the deutoxide.
These two oxides combine with most acids and form salts, some of which
exhibit remarkable differences occasioned by the oxides; thus, muriatic
acid with the protoxide forms protomuriate of mercury, commonly called
_calomel_, an insoluble salt; with the deutoxide it forms deutomuriate
of mercury, commonly called _corrosive sublimate_, a soluble salt.
The proportions of metal and oxygen in the two oxides may be found by
precipitating a known weight of mercury reduced by solution to either
of the oxides, then drying and weighing the oxides, when the increase
of weight by the addition of oxygen may be observed. This method is
less accurate with regard to mercury than to other metals, on account
of the very great weight of the atom, by which a small error in the
gross weight of the oxide will be a great one as it respects the
oxygen. This circumstance will partly account for the differences of
authors on this subject.
One fact has been for some time known which demonstrates the oxygen in
the red oxide to be double that in the black. Corrosive sublimate may
be reduced to calomel by adding to it as much mercury as the sublimate
contains, and triturating the mixture well, the oxygen of the red oxide
(as well as the acid) becomes equally divided amongst the mercury and
forms the black oxide, which is a constituent of calomel. Hence it
follows that if the oxygen in one oxide can be ascertained, that of the
other becomes known. Or if we can find how much oxygen must be added
to the black oxide to change it to the red, we shall know the oxygen
in both. Conformably with this last idea I have found a very accurate
and elegant method of ascertaining the oxygen required to convert the
black to the red oxide by treating protomuriate of mercury, mixed with
water and a little muriatic acid, with oxymuriate of lime in solution;
this must be gradually added till the protomuriate is dissolved, or
rather converted to the deutomuriate. The quantity of oxygen in a given
solution of oxymuriate of lime is most conveniently found by a solution
of green sulphate of iron, as will be shewn under the oxides of that
metal.
The oxides of mercury may be investigated by the nitrous gas produced
during solution. When mercury is dissolved without heat, as mentioned
above, no nitrous gas is liberated. The solution has a strong nitrous
smell and requires a great quantity of oxymuriate of lime to saturate
both the oxide and the acid. When heat is employed to accelerate the
solution, nitrous gas is liberated. I dissolved 154 grains of mercury
in nitric acid, 1.2 sp. gr., by the application of a gentle heat from
a lamp. About ⅒ excess of acid remained in the solution; the nitrous
gas obtained was 12 oz. measures = 7.5 grains, corresponding to 6.5
oxygen, which gives nearly 4 oxygen or 100 mercury. This would have
led me to suppose I had obtained the _black_ oxide in solution; it was
however entirely the _red_, as it gave no precipitate by common salt,
and exhibited the red oxide by lime water; but it required as much
oxymuriate of lime as contained 6.5 oxygen to saturate the _nitrous
gas_ in the solution before any oxymuriatic acid was liberated. It was
clear therefore that only ½ of the nitrous gas was evolved, and the
other ½ was retained in the solution, though it had been exposed to
boiling heat.
The following are the proportions assigned by the several authors for
the oxides of mercury.
Mercury. Oxygen.
+------------------+
black. red.
Bergman[4] 100 + 4 + --
Lavoisier[5] -- + -- + 7.75 to 8
Chenevix[6] -- + 12 + 18.5
Taboada[7] -- + 5.2 + 11
Fourcroy & Thenard[8] -- + 4.16 + 8.21
Sefstrom[9] -- + 3.99 + 7.99
My results give -- + 4.2 + 8.4
[Footnote 4: Kirwan’s Mineralogy.]
[Footnote 5: Annals of Philosophy, Vol. 3, p. 333.]
[Footnote 6: Philos. Trans. 1802.]
[Footnote 7: Jour. de Physique. 1805.]
[Footnote 8: Mem. d’Arcueil, Vol. 2. p. 168. 1809.]
[Footnote 9: Annals of Philosophy, Vol. 2. p. 48.]
Though the relative weights of oxygen and mercury may be investigated
as above, yet it is from the weight of mercury and the acids in the
salts of mercury, some of which are of a very definite character,
such as the muriate and the deutomuriate, that the relative weight of
the atom of mercury is best investigated. From these I first deduced
the weight of an atom of mercury to be 167 about 10 years ago, and
subsequent experience has not induced me to change the number, though
it probably may admit of some correction. If the atom of mercury be
denoted by 167, that of the protoxide will be 174, and that of the
deutoxide 181; which makes 100 mercury take 4.2 and 8.4 oxygen for the
oxides respectively, as in the above table.
5. _Oxide of Palladium._
The discoverer of this metal, Dr. Wollaston, has given us its
distinguishing chemical properties; but we are indebted to Berzelius
and Vauquelin for the proportions of oxygen and sulphur which combine
with the metal (Vid. Annal. de Chimie, 77 and 78.) Few chemists have
had an opportunity of making experiments on this metal, owing to its
great scarcity and the consequent high price of it (1 shilling per
grain). It does not seem desireable that any but those skilled in the
more delicate chemical manipulations should operate upon articles such
as the present.
Berzelius treated the muriate of palladium with mercury, which
abstracted the oxygen and left an amalgam of palladium and mercury;
from the quantity of mercury dissolved he calculates that 100 palladium
combine with 14.2 oxygen. This conclusion was corroborated by the
circumstance that 100 palladium were found to take 28 of sulphur,
or double the quantity of oxygen, which frequently happens with the
metals.
Vauquelin precipitates the oxide of palladium from the muriate by
potash; it appears of a red brown colour, and is probably a hydrate;
when washed and dried in a moderate heat, it becomes black, it loses 20
per cent. by a red heat and becomes metallic. This would give 25 oxygen
on 100 metal; but as he finds the sulphuret to be 100 metal with 24 or
30 sulphur, nearly agreeing with Berzelius, it is very probable that a
moderate heat does not free the oxide from water, and that consequently
a part of the 20 per cent. loss is water.
I dissolved 3 grains of palladium in a small excess of nitro-muriatic
acid and obtained 240 grain measures of nitrous gas; the same quantity
was obtained a second time, and to the solution (slightly acid) were
added by degrees 200 measures of oxymuriatic acid gas; after agitation
no smell was perceived, but by increasing the quantity of gas a
permanent smell of oxymuriatic acid was produced, and when 200 more
had been added the smell was sensible for some days in an open jar, a
presumption that no higher oxide is to be obtained. Now 240 nitrous gas
= .32 of a grain, corresponding to .28 of oxygen, and 200 oxymuriatic
acid = .64 of a grain, corresponding to .15 oxygen; the sum of the
two portions of oxygen = .43, which must have combined with 3 grains
of palladium; if .43 ∶ 4 ∷ 7 ∶ 50 nearly. Or 100 metal combine with
14 oxygen, as determined by Berzelius. I find the sulphuret to accord
with this determination; and by carefully saturating the excess of
acid in the nitro-muriate of palladium and then finding the quantity
of lime water necessary to precipitate a certain weight of palladium,
as well as the quantity of test muriatic acid necessary to dissolve
the precipitated oxide, I am confirmed in the opinion that the atom of
palladium must weigh 50 nearly, and its oxide 57, which there is every
reason to believe is the protoxide.
6, 7, _and_ 8. _Oxides of Rhodium, Iridium, and Osmium._
Nothing certain has yet been determined respecting the oxygenation of
these very rare metals.
9. _Oxides of Copper._
There are two oxides of copper according to the results of Proust,
Chenevix, Berzelius and others, the proportions of which are given
nearly the same by all, and so as to leave no reasonable doubt
concerning their accuracy.
1. _Protoxide._ This oxide is _orange_, and contains 12½ oxygen on
100 copper: it is obtained by precipitating a portion of copper from
the solution of any cupreous salt, by means of iron, then mixing this
copper with a rather greater portion of the deutoxide and triturating
them well. This being done, the mixture is to be dissolved in muriatic
acid, and the orange oxide may then be precipitated by an alkali.
2. _Deutoxide._ This oxide is _black_; it contains 25 oxygen on 100
copper: the _black_ oxide is obtained by dissolving copper in nitric
or sulphuric acid, then precipitating by lime water or an alkali, and
heating the dried precipitate red hot. It may also be obtained by
exposing copper to a red heat for some time in common air or oxygen
gas, removing the scales and exposing them in like manner, till at
length the black oxide is formed.
By dissolving 112 grains of copper turnings in 1000 grain measures
of 1.16 nitric acid, I obtained 48 oz. measures of nitrous gas, = 30
grains; by oxymuriate of lime I found 2 grains of nitrous gas in the
solution, making in all 32 grains = 28 grains of oxygen. If 28 ∶ 112 ∷
14 ∶ 56, for the weight of an atom of copper; hence the protoxide = 63
and the deutoxide = 70. These weights I adopted in 1806, and have not
seen any reason to modify them since.
10. _Oxides of Iron._
Two well known and well distinguished oxides of iron are now
universally admitted; the one contains 28 oxygen on 100 iron, the other
42 on 100.
1. _Protoxide._ This is always formed when iron is dissolved in dilute
sulphuric or muriatic acid; it may be precipitated from these solutions
by the pure alkalies or earths; it appears at first of a dark green,
being then a hydrate or combined with water; on a filtre it soon
becomes yellow at the surface by attracting oxygen; when dried in a
heat of 200° or upwards it becomes black. The quantity of oxygen in it
is best ascertained from the hydrogen generated during the solution
of the iron. All the authorities I have found nearly concur in their
results as under.
100 grains of iron dissolved in dilute sulphuric or muriatic acids
yield hydrogen, according to
Cavendish (1766) 155 cubic inches.
Priestley, from 147 to 162
Lavoisier 163
Vandermonde, Berthollet, } max. 176
and Monge }
Vauquelin 160 to 179
Dr. Thomson 163
My own Experiments give 160
----
Mean 164 = 82 oxygen =
27.9 grains.
By precipitating the oxide, and drying it, nearly the same result may
be obtained, as 100 iron will yield 128 oxide. This oxide is magnetic.
2. _Intermediate or red oxide._ This oxide may be obtained in various
ways. First by calcining the sulphate or nitrate of iron. Second by
precipitation from old solutions of the salts of iron; the precipitate
is _yellow_ at first, being perhaps a hydrate; but when dried and
heated it becomes brown-red. Third, by calcining iron or repeatedly
exposing iron filings to a red heat, and trituration. Fourth, by
treating a solution of the sulphate or other salt of the protoxide
with oxymuriatic acid, or oxymuriate of lime till oxymuriatic acid is
evolved; then precipitating the oxide which is thus converted into
the red. Fifth, by agitating water containing the green oxide recently
precipitated, with oxygen gas. The red oxide is not sensibly magnetic.
The quantity of oxygen in the red oxide may be investigated in various
ways, and it is generally allowed that they all concur in giving 42 on
100 iron. The one which I have used peculiarly, and prefer both for
ease and accuracy, is to find the quantity of oxymuriatic acid gas
necessary to saturate a given portion of the green sulphate. I take for
instance 100 measures of 1.149 green sulphate, which I know to contain
8 grains of black oxide; this I find absorbs nearly 13 hundred measures
of oxymuriatic acid gas before the acid smell is developed; the
oxygen corresponding to this quantity of acid is known to be near 660
measures, = .88 grain. (See VOL. 1, p. 308.) Hence, if 8 ∶ .88 ∷ 128
∶ 14; or 128 black oxide acquire 14 or become 142 when converted into
the red oxide. This fact being established, I find it very convenient
to make use of the oxymuriate of lime instead of the acid gas, adopting
the solution of green sulphate of iron as a test of the quantity of
oxymuriatic acid in a given volume of any solution of oxymuriate of
lime.
The quantity of oxygen in the red oxide of iron may be inferred,
but not so satisfactorily, from the nitrous gas obtained during the
solution of iron in nitric acid. In order to obtain the most gas from
a given quantity of the materials, they should be so proportioned
as to produce saturation nearly. If an excess of acid be used, it
absorbs the nitrous gas in part; and if an excess of iron, it is not
all dissolved. I took 50 grains of iron filings and 600 measures of
1.15 nitric acid; these were put together in a gas bottle and by the
assistance of a little heat a quantity of nitrous gas was obtained
equal to 12 grains in weight, allowing the sp. gr. of the gas to be
1.04 (air being 1); all the iron was dissolved except a few atoms, and
the solution was slightly acid; the whole of the oxide was red when
precipitated by lime water. Now 50 grains of iron take 21 of oxygen to
form the red oxide, and these correspond to 24 of nitrous gas, which
is just twice the quantity obtained; one half of the gas generated
then remains in combination with the iron, even when the constituents
of the salt are proportioned so as to produce mutual saturation. I
was in expectation that the quantity of nitrous gas retained might be
converted into nitric acid by oxymuriate of lime, and hence might be
determined; but in this I was disappointed. When oxymuriate of lime is
added to the liquid, a pungent gas is liberated, the nature of which I
have not determined. Thinking it might in part be owing to the iron,
I transferred the acid to soda, by decomposing the nitrate of iron
by the carbonate of soda; this nitrate of soda however, when treated
with oxymuriate of lime, exhibited the same phenomenon as the nitrate
of iron. When an acid is added the oxymuriatic acid itself is given
out. These results will require further consideration. At present I am
inclined to think the pungent gas is one atom of nitrous and one of
oxygen or what I formerly considered as nitric acid. (See VOL. 1, plate
4, fig. 27.)
Some authors have found as they conceive, other oxides of iron,
containing less or more of oxygen than the above; thus Darso finds by
calcination from 15 to 56 oxygen on 100, (Nicholson’s Journ. VOL. 17);
but there is great reason to believe that uncertainties must exist
in his mode of experimenting sufficient to account for the anomalies
observed. This author has suggested some doubt whether the oxygenous
gas naturally contained in water has any effect on the salts with green
oxide of iron. I have ascertained that point by repeated experiments,
and can assert that the oxygen in water immediately unites to the green
oxide of iron to convert it into red, and that the green sulphate may
be used as an accurate test of the quantity of oxygen in water. When
pure green sulphate of iron is dropped into water and then the oxide
precipitated by a gradual addition of lime water, it falls down yellow
in proportion to the oxygen in the water, which may be increased 3
or 4 times by artificial impregnation. If the oxygen of the water
be previously saturated with nitrous gas, then the oxide is wholly
precipitated green.
Gay Lussac, in the 80th VOL. of the Annal. de Chimie, asserts that an
oxide of iron containing 37.8 oxygen upon 100 iron is always obtained
when iron is burned in oxygenous gas, and still more effectually
when iron is oxydized by water or steam. If this oxide exist in the
proportions stated, it must be a compound of 1 atom of the protoxide
and 2 of the red oxide, which would give 37.3 oxygen on 100 of iron.
From the above facts and observations it is evident the atom of iron
must be considered as weighing 25, (and not 50 as already given, VOL.
1, page 258); the protoxide is 32, and the intermediate or red oxide is
2 atoms protoxide and 1 of oxygen = 71.
11. _Oxides of Nickel._
1. _Protoxide._ It appears to be ascertained from the experiments of
Proust (Journ. de Physiq. 63--442), Richter (Nichols. Jour. 12.),
Tupputi (An. de Chimie 78.), and Rolhoff (An. of Philos. 3--335.),
that the protoxide of nickel consists of 100 metal and from 25 to 28
oxygen. My experiments on the solution of nickel in nitric acid give me
14 grains nitrous gas, corresponding to 12 oxygen, in the solution of
44 grains of nickel; this gives 100 nickel to 27 oxygen, which I adopt
as agreeing with the mean of the beforementioned results. This oxide
may be obtained by precipitation from a solution of nitrate of nickel;
it is at first white, being then a hydrate; when dried in a moderate
temperature it becomes yellowish; after this, being heated to a cherry
red, it loses from 20 to 24 per cent. of water and becomes of an ash
grey colour: this is the only oxide of nickel soluble in acids, and
must therefore be deemed the protoxide: hence we have 27 ∶ 100 ∷ 7 ∶
26, nearly, for the weight of an atom of nickel; and not 25 or 50, as
estimated at page 258. VOL. 1.
_Intermediate oxide._ Thenard discovered a second oxide of nickel
by passing oxymuriatic acid through a solution of nickel and then
precipitating; it is a black powder; when treated with sulphuric
or nitric acid it gives out gas, being the excess of oxygen above
the protoxide; but with muriatic acid it gives oxymuriatic acid
gas. Rolhoff was induced to believe, but I do not know upon what
evidence, that this oxide contained 1⅓ or 1½ times the oxygen of the
protoxide. By means of oxymuriate of lime I find the protoxide recently
precipitated, takes half as much oxygen as it had previously, to form
the black oxide; and that it cannot be formed, like the red oxide of
iron, by agitation with water mixed with common air. The white oxide
treated with oxymuriate of lime becomes almost instantly blue, growing
darker till it gradually passes into brown, and finally black in about
half an hour. It contains 40 oxygen on 100 nickel, and is most probably
constituted of 1 atom of oxygen holding 2 of protoxide together, more
especially as it is not found in combination with acids. The method
I prefer to procure the black oxide is to precipitate a known weight
of oxide by lime water; then pouring off the clear liquid, I put as
much liquid oxymuriate of lime to the moist hydrate as contains ⅒ of
the weight of the oxide of oxygen, and stir frequently for half an
hour; the point of saturation is found when more oxide put to the clear
liquid is not discoloured on one hand, and when more oxymuriate of lime
does not affect the colour, but remains in the clear liquid on the
other hand.
12. _Oxides of Tin._
There are two oxides of tin, which have been carefully investigated by
several chemists, and appear to be ascertained with great precision.
The protoxide is _grey_, and contains 13½ oxygen on 100 tin; the
_deutoxide_ is _white_, and contains 27 oxygen on 100 tin.
1. _Protoxide._ There are two methods of obtaining the constitution
of this oxide. The first is by dissolving a certain weight of tin
filings in muriatic acid, precipitating by lime water or carbonated
alkalies and drying the oxide in a moderate heat; this is liable to
some uncertainty; the precipitate being a _hydrate_, requires to be
exposed to heat to expel the water; but if the heat approaches to red,
the oxide takes fire and is converted into the deutoxide. The second
method is to dissolve tin in muriatic acid and carefully collect the
hydrogen gas evolved; this was first done by Mr. Cavendish, with his
usual accuracy, and published in 1766; he found 1 oz. of tin yield 202
oz. measures of hydrogen gas. I have frequently tried this experiment
and always found a proportional quantity, or very nearly 200 measures
for each grain of tin. This mode of investigation appears to me
unexceptionable. Now 200 hydrogen unite to 100 oxygen, and 100 grain
measures of oxygen = .134 grain in weight; hence if .134 oxy. ∶ 1 tin ∷
7 oxy. ∶ 52 nearly for the weight of an atom of tin, on the presumption
this is the protoxide.
2. _Deutoxide._ This may be obtained by heating tin till it takes
fire, and the produce of the combustion is the oxide required; but
to ascertain the proportions of tin and oxygen two other methods are
preferable; the one is to treat tin with nitric acid of the sp. gr.
1.2 to 1.4; a violent effervescence and great heat ensue and the tin
is converted into a white powder. This being dried in 100° gives
about 160 grains for 100 of tin. It consists of the deutoxide united
to a little acid and water; these two may be driven off by a low red
heat, and 127 grains of the deutoxide remain in the state of a white
powder. The other method is to treat a solution of the protoxide of
tin with oxymuriate of lime till it is saturated; this will be found
when 59 grains of the protoxide have acquired 7 grains of oxygen, or
113½ grains of the deutoxide have acquired 13½ grains of oxygen, which
corroborates the result by the 1st method. This oxide containing just
twice as much oxygen as the former, may justly be considered as the
deutoxide. No higher oxide of tin has been obtained.
The two oxides, though both white when precipitated, may be
distinguished from their different appearances; the first is _curdy_,
the second, _gelatinous_.
It may be proper to subjoin authorities for these oxides:
Tin Protoxide Deutoxide
Cavendish, from the hydrogen 100 113.5 --------
Proust (Journ. de Physique 59-341) 100 115 127½.128[10]
Gay Lussac (Annal. de Chimie 80-170) 100 113.5 127.2[11]
Berzelius (Annal. de Chim. 87-55) 100 113.6 127.2[12]
My own, as above 100 113.4 127
[Footnote 10: By nitric acid, the result of 3 experiments all agreeing
for the deutoxide; the protoxide is by calculation and less certain. He
afterwards adopts 13.6 from Berzelius. Journ. de Phys. Aug. 1814.]
[Footnote 11: The protoxide from hydrogen by solution; the deutoxide by
transmitting steam over the metal at a red heat.]
[Footnote 12: The 2d. by oxydizing the sulphuret of tin by nitric acid;
the 1st. by inference only, one half of the oxygen of the 2d.]
13. _Oxides of Lead._
There are three oxides of lead now generally recognized, the _yellow_,
the _red_, and the _brown_, the proportion of oxygen in each of which
has been investigated by several chemists whose results do not well
accord with each other. I shall treat of them under the following
names, namely the _protoxide_, the _intermediate oxides_, and the
_deutoxide_, for reasons which will appear.
1. _Protoxide._ The yellow oxide of lead is the only one capable of
forming salts with acids. Lavoisier found the oxygen of this oxide
combined with 100 lead to be 4.47; Wenzel, 10; Proust, 9; Thomson,
10.5; Bucholz, 8; Berzelius, 7.7. This last accords best with my own
experience; but it is chiefly from the other combinations of lead, that
the weight of its atom as well as that of the protoxide are determined
and confirmed, as lead forms several very definite compounds with
acids, &c. The quantity of oxygen in the protoxide may be found by
several methods, as under.
1st. By dissolving a given portion of the oxide in acetic acid, and
precipitating the lead by another metal, as zinc; in this case the
oxygen of the lead goes to the zinc which becomes dissolved, and from
the loss of weight of the zinc and the proportion of oxygen in zinc
oxide being previously known, and the weight of the precipitated lead
being found, we have data for determining the oxide of lead. I took 200
measures of acetate of lead solution (1.142), which I knew contained
27 grains of oxide of lead; this being diluted with an equal volume of
water, the lead was precipitated by a rod of zinc; in 6 hours an _arbor
saturni_ was formed which was collected and well dried; it weighed
21¾ grains, and the zinc rod had lost 7 grains: care must be taken
in performing this experiment that all the lead be not precipitated,
otherwise the oxide of zinc begins to fall, and the result is
uncertain. In the residuary liquid I got 4 grains of sulphate of lead
by sulphuric acid. Here then we have the oxygen of 21¾ lead transferred
to 7 zinc; but if 7 ∶ 21¾ ∷ 29 ∶ 90 nearly. Now it is known that 29
parts of zinc take 7 of oxygen, therefore 90 lead take 7 of oxygen, and
the atom of lead = 90, and the protoxide 97.
I formerly stated the atom of lead 95. VOL. 1, page 260.
2. By dissolving 180 grains of lead in nitric acid in a small thin
capsule, and heating it till the salt was quite dry, I got 288 grains
of salt, weighed in the capsule; 36 grains of this salt yielded 24¼
yellow oxide by a low red heat = 22½ lead. This gives 90 lead to 7
oxygen.
3d. Again, 36 grains of the above salt, dissolved in water,
precipitated by ammonia, and well washed on a filter, gave 23+ grains
of oxide separated from the filter, and this had acquired 1 grain,
making 24+ grains of oxide from the 22½ lead as before; the residue of
liquid gave no signs of lead by hydrosulphuret of ammonia. The same
quantity of salt precipitated by an excess of lime water gave only 22
grains of oxide; but hydrosulphuret of ammonia precipitated 2+ grains
of sulphuret of lead from the clear liquid.
II. _Intermediate oxide or oxides._ Minium or red lead, &c. Minium
is an article of commerce used as a pigment and for various other
purposes. It is made by exposing the yellow or protoxide of lead finely
pulverized to a low red heat in a current of air, and constantly
stirring the oxide so as to expose fresh particles to the air. In
two days the yellow oxide is converted into the red. Several authors
observe that red lead usually contains 1, 2, or more grains per cent.
of impurities insoluble in nitric and acetic acids; the specimen I
used however was so pure as not to leave more than ⅓ of a grain per
cent. of insoluble matter after being heated red and treated with
dilute nitric acid.
Some of the most remarkable properties of red lead are, 1st. It is
never obtained in combination with any acid; 2d. It yields oxygen gas
when exposed to a bright red heat or when treated with concentrated
sulphuric acid, and is in both cases reduced to the protoxide; 3d. When
treated with dilute nitric acid it is dissolved in part, but constantly
leaves an insoluble brown residuum, which is the deutoxide, as will be
shewn; the weight of the deutoxide obtained is by my experiments 20 per
cent. and the part in solution is found to be the protoxide; 4th. When
treated with muriatic acid, muriate of lead is formed and oxymuriatic
acid given out; 5th. When treated with dilute acetic acid or cold
concentrated acetic acid, ½ of the oxide is dissolved and the remainder
is still red, its colour being rather improved; if concentrated acid be
used and boiling heat applied, then ⅘ of the whole oxide is dissolved
and ⅕ remains of brown oxide, the same as with nitric acid.
Some of the above facts are new, and may contribute to elucidate this
most curious oxide, which scarcely has a parallel. Proust is the only
author I know who has given a plausible conjecture concerning the
peculiar nature of this oxide. He supposes it a compound of the yellow
and brown oxides. This I believe is the fact; but it will be found I
apprehend to be a compound of 1 atom of oxygen with 6 of the yellow
oxide, as will appear from what follows.
Respecting the quantity of oxygen in the red oxide, Lavoisier finds
9 oxygen to 100 lead, Thomson 13.6, and Berzelius 11.55. This last
is partly from experience and partly from a supposed analogy, that
the successive oxides of the same metal contain oxygen as 1, 1½ and 2
respectively; and having found (I believe) correctly, that the brown
oxide contains just twice as much oxygen as the yellow, this ingenious
and generally accurate author adopts the theoretic inference in this
instance at least prematurely, and concludes the red oxide is the mean
between the yellow and the brown. But we must appeal to experience.
It has already been stated that when red lead is exposed to heat,
oxygen gas is given out, and it may be added, a small trace of water;
and yellow oxide remains.
This experiment requires considerable skill. If too great a heat is
used, a part of the lead is reduced or revived as it is termed; if
too little heat, then a part of the red lead remains unaltered. In
performing this experiment I use a small clean iron spoon to hold the
red lead, and cover it by another iron spoon; the whole is then held
by a pair of tongs in a red fire till the spoon exhibits a uniform
moderate red, and some time after.
It is then withdrawn and cooled, and the oxide weighed. The average
loss of weight is nearly 2 grains per cent. If only 1 grain or less,
a considerable portion of red oxide remains mixed with the yellow; if
3 or more grains, then the margin of the oxide exhibits particles of
lead amounting to ⅒, less or more, of the original weight; this can be
easily separated from the oxide if necessary, but it is apt to adhere
to the iron; when red oxide remains, it is so mixed with the yellow
as not easily to be separated, but its quantity may be determined by
nitric acid, which dissolves the yellow, and ⅘ of the red, leaving a
residuum of brown oxide, from which the quantity of red is inferred.
Now if the loss of weight of 100 red oxide be only 2 grains, and a
part of that be water, it is impossible that 115.55 should lose 3.85
grains of oxygen, according to Berzelius. Another experiment, equally
decisive of the question, is to determine the quantity of oxygenous gas
to be obtained by heat or acids from a given weight of red lead. In one
experiment made with great care, 500 grains of red oxide gave 6 grains
of oxygenous gas by sulphuric acid; in another, 200 yielded 2½ grains.
In order to vary the mode of determining the quantity of oxygen,
into 210 measures of test green sulphate of iron solution, (1.156) =
16.8 green oxide, put 160 grains of minium; to this was added dilute
muriatic acid more than sufficient for the minium: The oxymuriatic acid
from the oxygen of the minium was instantly seized by the oxide of the
iron, the whole of which was found by precipitation to be changed from
green to red and an excess of oxymuriatic acid appeared. Now 16.8 oxide
would require 1.86 oxygen to become red, which it must have acquired
from 160 of red lead; or 100 red lead yielded 1.2 oxygen, the same
proportion as by sulphuric acid. These experiments point out 1.2 oxygen
in 100 red lead as the excess which converts the yellow to the red
oxide. Were any doubt to remain on the subject, the experiment with
nitric acid and red oxide will remove it. If the red oxide contained
a mean of oxygen between the yellow and the brown, when it is treated
with nitric acid more than 50 per cent. of brown oxide would be
obtained instead of 20, which is contrary to all experience. It must
be observed that Berzelius informs us he extracted the yellow oxide,
mechanically mixed (as he conceives) with the red oxide, by digestion
with dilute acetic acid; but he does not inform us how much per cent.
his minium was reduced by this operation. From what is stated above, it
appears that about ½ of the whole is thus dissolved. The remaining half
would then contain double the quantity of oxygen and brown oxide per
cent. that the original did. Still these quantities are inadequate to
explain the phenomena. Besides it cannot be admitted that a _red_ and
a _yellow_ powder can be intimately mixed in equal quantities and the
mixture not be distinguishable without difficulty from the _red_ one,
and be altogether different from the _yellow_. We must then conclude
that the minium of commerce (such as I have used) is a true chemical
compound.
Grounding our reasonings upon the preceding facts, there are but
two suppositions that can be considered as plausible, respecting
the constitution of the red oxide. It may be 1 atom of oxygen and
5 of yellow oxide, or 1 atom of oxygen and 6 of yellow oxide. The
former would give 1.4 per cent. extra oxygen in 100 red oxide, and 21
brown oxide; the latter would give 1.2 per cent. extra oxygen and 18
brown oxide. I adopt the latter supposition; because it agrees with
experiment in regard to oxygen, and gives the brown oxide a little
_lower_ than experiment, as may be expected on two accounts; first, the
residue of brown oxide contains the insoluble dross of the red oxide
(which was very small however, as stated above); and, second, unless a
considerable excess of nitric acid be used, or long digestion, a small
portion of the red oxide escapes decomposition. Another and still more
important consideration, as to the question whether 5 or 6 atoms, is
the equal division of the red oxide by the operation of cold acetic
acid; it reduces the 1 oxygen and 6 yellow oxide to 1 and 3 atoms;
whereas if we adopt the other, we must conclude it reduces the 1 and 5
to 1 and 2½, a position that cannot well be reconciled to the atomic
theory.
According to this conclusion then the red oxide of lead or minium of
commerce is constituted of 1 atom of oxygen holding 6 atoms of yellow
oxide together; or it is composed of 100 lead and 9.07 oxygen. When
it is digested in cold acetic acid the residuum constitutes another
oxide consisting of 1 atom of oxygen and 3 of yellow oxide, or 100
lead and 10.4 oxygen, possessing the same colour as the former, but
distinguishable by its not being acted on by cold acetic acid, and by
its containing twice as much brown oxide and extra oxygen as minium. No
doubt the other intermediate oxides of 1 to 4 and 1 to 5 exist, and are
all alike red; but have not perhaps any remarkable distinctions besides
their containing different proportions of oxygen and brown oxide.
Whether an oxide consisting of 1 oxygen and 2 yellow oxide exists, I
have not discovered; but that 1 oxygen and 1 yellow oxide are found
united, appears below.
III. _Deutoxide._ This is the flea-brown oxide mentioned above. It may
also be obtained by treating solutions of salts containing the yellow
oxide by oxymuriate of lime, in which case the oxide is precipitated,
leaving the acid in the liquor, a proof that it is insoluble in
acids. Its more remarkable properties are: 1st. like the red oxide,
when heated to a low red, or treated with sulphuric acid, it yields
oxygenous gas, and more copiously; it is thus reduced to the yellow
oxide: 2d. with muriatic acid it yields oxymuriatic acid in great
plenty and muriate of lead: 3d. it detonates when rubbed with sulphur
in a mortar.
The quantity of oxygen in the brown oxide is stated by Thomson at 25
oxygen to 100 lead, by Berzelius at 15.6 to 100. This last is very
nearly right by my experience, and being just double of the oxygen
in the protoxide, it warrants us in denominating it the deutoxide.
Berzelius finds 100 of the brown oxide lose 6.5 by a red heat so as
to reduce it to the yellow; Dr. Thomson finds the loss 9 grains. This
difference is easily accounted for; it loses, I find, from 7 to 10
grains per cent. according to the previous degree of dryness; when
exposed to a moist atmosphere it attracts humidity; when dried in a
temperature of 200° and exposed to red heat immediately after, it does
not lose more than 6.5 or 7 per cent. This is corroborated too by the
oxygen expelled by sulphuric acid. From 100 grains of brown oxide and
sulphuric acid in a gas bottle, I obtained by the heat of a lamp 8.3
oz. of oxygenous gas = 5.3 grains; about 120 grains of grey sulphate
of lead were left in the bottle. The oxygen is rather less than was
expected; but it must be remembered that 100 grains of brown oxide,
obtained in the ordinary way, have the insoluble dross of 500 red oxide
in them, which must have some influence in diminishing the production
of oxygen.
Though the above might be deemed sufficient to demonstrate the
proportion of oxygen in the brown oxide, I was desirous to corroborate
the results by oxymuriate of lime. I found repeatedly that 100 grain
measures of acetate of lead (1.142) = 13.8 yellow oxide, required 400
measures of oxymuriate of lime = 1 oxygen, to precipitate the whole of
the oxide in a brown state. Now if 13.8 ∶ 1 ∷ 97 ∶ 7. Again, into 240
measures of test green sulphate of iron (1.156) = 19 oxide, were put
40 grains of brown oxide of lead, together with a sufficient quantity
of muriatic acid to saturate the lead, and discharge the oxygen; after
due agitation sulphate of lead was precipitated, and the whole of
the oxide of iron was found, when precipitated, to be yellow. But 19
grains oxide of iron require 2+ of oxygen to become yellow; hence the
40 grains brown oxide of lead must have furnished 2+ grains of oxygen
to form oxymuriatic acid, which transferred it to the oxide of iron.
If 40 ∶ 2+ ∷ 100 ∶ 5+ oxygen, for the excess or second dose of oxygen
in 100 brown oxide, such as is obtained by nitric acid along with its
impurities; which agrees with the results obtained by the other methods.
14. _Oxide of zinc._
When zinc is exposed to a strong heat it burns with a brilliant white
flame, and a white powder sublimes, which is the oxide of the metal.
When dilute sulphuric acid is poured on granulated zinc, hydrogen
gas is produced in great abundance and purity; the metal is oxidized
at the expence of the water and dissolved in the acid, the oxide may
be precipitated by an alkali; it is white both when precipitated
and dried, and when heated does not differ from that obtained by
combustion. By a violent heat it runs into glass.
The quantity of oxygen in zinc oxide is, I think, best estimated by
the hydrogen gas produced during the solution; it may also be obtained
by direct combustion, or by solution in nitric acid and calcination.
Dr. Thomson determines the oxygen by comparison of the weights of real
sulphuric acid and metallic zinc in a solution of sulphate of zinc,
along with the consideration that the proportion of sulphuric acid and
oxygen in the metallic sulphates is known; Mr. Cavendish obtained 356
oz. measures of hydrogen from 1 oz. of zinc by solution. I dissolved 49
grains of zinc in dilute sulphuric acid and obtained hydrogen, after
the rate of 363 grain measures for 1 grain of zinc = 182 measures of
oxygen = .24 grain of oxygen.
The following are the principal authorities for the quantity of oxygen
in zinc oxide, in the order of time.
Zinc. Oxygen.
1766. Cavendish 100 + 23.3
1785. Lavoisier -- + 19.6
1790-1800. Wenzel and Proust -- + 25
1801. Desorme and Clement -- + 21.7
Davy -- + 21.95
Berzelius -- + 24.4
Gay Lussac -- + 24.4
Thomson -- + 24.42
My own -- + 24
Now if 24 oxy. ∶ 100 zinc ∷ 7 oxy. ∶ 29 zinc, nearly, which is
therefore the weight of an atom of this metal, on the supposition that
the oxide is 1 oxygen and 1 metal; and the atom of oxide = 36.
I formerly estimated the atom of zinc at 56 (VOL. 1, page 260). This
was occasioned by taking the above as the _deutoxide_ instead of the
_protoxide_. By violently heating the oxide of zinc in a close vessel,
Desorme and Clement reduced the oxygen nearly one half, so as to
afford a presumption that an oxide with half the oxygen of the common
one subsisted. Since that time some observations of Berzelius seem to
shew that a suboxide of zinc exists. It does not appear however, that
such oxide is ever found in combination with acids; and, granting the
accuracy of the observations, it is rather to be presumed to be the
semi-oxide, or 1 atom of oxygen and 2 of metal, than the protoxide.
No higher oxidation of zinc than the above has yet been obtained, and
probably does not exist.
15. _Oxides of potassium._
Since writing the articles “potassium and sodium,” in the former
volume, a very important essay relating chiefly to these subjects has
been written by Gay Lussac and Thenard (a copy of which they were so
good as to send me), entitled “Recherches Physico-chimiques, &c.” in
2 VOL.--Many of the most interesting experiments of Davy have been
repeated on a larger scale, and a great number of original ones added;
these ingenious authors endeavour to sum up the evidences for and
against the two hypotheses concerning potassium and sodium, namely,
as to their being metals or hydrurets, and upon the whole incline to
the former, allowing however, that the facts afford great plausibility
to both. One thing they seem to have discovered and established, that
the new bodies or metals admit of various degrees of oxidation, and
of course these products have a claim to be classed amongst oxides in
general though the nature of their bases may still be an object of
dispute.
They find three oxides of potassium; the lowest degree is obtained
by exposing potassium to atmospheric air in a small bottle, with a
common cork; a gradual oxidation takes place; a blueish grey brittle
product is obtained; there does not appear however, to be any proper
limit to this oxidation besides that which they admit as characterizing
the second degree or potash, which degree of oxidation may always
be immediately obtained by placing potassium in contact with water.
This I think should be called the protoxide and considered as 1 atom
of potassium, and 1 of oxygen; before this point it is potassium and
potash mixed or perhaps combined.
Besides these there is another obtained by burning potassium in oxygen
gas at an elevated temperature; this oxide is yellow, fusible by heat,
and crystallizes in lamina on cooling; it contains three times as much
oxygen as potash; put into water it is suddenly decomposed, giving out
⅔ of the oxygen in gas and becoming potash. Very probably an oxide
containing twice as much oxygen as potash might be formed with some
mark of discrimination, by uniting 18 parts potassium with 56 of yellow
oxide, but this has not yet been done.
According to these conclusions the weights of the oxides of potassium
may be stated as under.--Potassium 35, protoxide or potash 42,
deutoxide (supposed to exist) 49, and the yellow or tritoxide 56. Hence
we have
Potassium. Oxygen.
Protoxide (potash) 100 + 20 } Gay Lussac & Thenard
19 } Davy
Deutoxide 100 + 40 (unknown)
Tritoxide 100 + 60 Gay Lussac & Thenard
One feels unwilling to admit of a _tritoxide_, (and that perhaps the
only one existing,) when the deutoxide is unknown, were it not upon
good authority. The obscurity on this subject may be removed by future
experiments.
It may be proper to add that Gay Lussac and Thenard concur with Davy
in assigning a much greater saturating power to potassium and sodium
than to the fused hydrates of potash and soda of equal weights. From
the table, Recherches, Tom. 2, p. 214, it may be deduced that 35
potassium require as much sulphuric acid to saturate them as 50 or
more of the hydrate of potash; and that 21 sodium are equivalent to 36
or 37 hydrate of sodium. If these results are accurate, the weights
of potassium and sodium, considered as hydrurets, cannot be as we
have deduced them at pages 486 and 503, VOL. 1, namely, 43 and 29
respectively, but 35 and 21, as at page 262.
16. _Oxides of sodium._
Gay Lussac and Thenard find a suboxide of sodium in the same way as
that of potassium, and it is probably a compound of soda and sodium:
the remarkable oxidation which produces soda is, I should imagine, the
protoxide or one atom to one, as obtained by placing sodium in contact
with water. A higher oxide is obtained as with potassium, by burning
sodium in oxygen gas with a vivid heat. It resembles the yellow oxide
of potassium in its appearance and properties. The degree of oxidation
varies in the different experiments from 1¼ to 1¾ times the oxygen of
soda. It is probably a combination of the protoxide and deutoxide.
Hence the oxides of sodium may be as under; reckoning the atom of
sodium 21, and soda 28.
Sodium. Oxygen.
Protoxide (Soda) 100 + 33⅓
Intermediate oxide 100 + 50
17. _Oxide of bismuth._
Only one oxide of bismuth is known, and the proportion of its parts has
been gradually approximated by Bergman, Lavoisier, Klaproth, Proust,
and others. Berzelius mentions a purple oxide obtained by exposing
bismuth to the action of the atmosphere; but as no experiments have
been made upon it, we cannot adopt it at present. According to Klaproth
and Proust, 100 bismuth unite with 12 oxygen; but by the more recent
experiments of Mr. J. Davy and Lagerhjelm 100 bismuth take 11.1 or 11.3
oxygen. If we adopt this last, which is doubtless near the truth; we
shall have 11.3 ∶ 100 ∷ 7 ∶ 62 for the weight of the atom of bismuth,
on the supposition that the compound is the protoxide or 1 atom of
metal to 1 of oxygen. My former weight of bismuth was 68 (page 263),
which is clearly too high.
Bismuth is best oxidized by nitric acid. Part of the oxide combines
with the acid and part precipitates in the state of a white powder; if
the whole be gradually heated, the acid is driven off, and at a low red
the oxide remains pure; it is fused into glass and of a red or yellow
colour, according to the heat employed. Bismuth may also be oxidized by
heat in open vessels; yellow fumes arise which may be condensed and are
found to be the oxide.
18. _Oxides of antimony._
Considerable difference of opinions exists with regard to the oxides
of antimony. Proust finds two oxides which he determines to consist,
the first, of 100 metal + 22 or 23 oxygen; the second of 100 metal +
30 oxygen. Thenard finds 6 oxides: J. Davy two oxides, namely, 100
metal + 17.7 oxygen, and 100 + 30 oxygen. Berzelius infers from his
experiments that there are 4 oxides of antimony, the first containing
4.65 oxygen, the second 18.6, the third 27.9, and the fourth 37.2 of
oxygen on 100 metal. He admits however that the oxide obtained by
boiling nitric acid on antimony and expelling the superfluous acid by
a low red heat, consists of 100 metal + 29 to 31 oxygen, as determined
by Proust and others. This is certainly the most definite of the
oxides, next to that which is obtained from the solution of antimony
in muriatic acid. This last may be had by pouring water into a solution
of muriate of antimony; a white powder precipitates, which is the oxide
with a little muriatic acid; the acid may be abstracted by boiling
the precipitate in a solution of carbonate of potash. This oxide is a
grey powder, and fusible at a low red heat. It enters exclusively into
various well known compounds, as the _golden sulphur of antimony_,
_antimoniated tartrate of potash_, &c. Its constitution, according to
Proust, is 100 metal + 23 oxygen; but J. Davy finds only 17.7 oxygen,
and Berzelius 18.6. As this oxide possesses the most distinct features,
and besides is the most important, it is desirable its constitution
should be ascertained without doubt. From several experiments I made on
the precipitation of antimony by zinc, I conclude the oxide contains
about 18 oxygen on 100 metal. I took the common muriate of antimony
with excess of acid, and immersed a rod of zinc into it, covering the
whole with a graduated bell glass. Hydrogen gas was produced by the
excess of acid, and its quantity was ascertained; the antimony was in
due time precipitated, and when the operation ceased, the loss of zinc
and the weight of antimony were found. For instance, to 50 measures
of 1.69 mur. ant. 60 water were added, no precipitation was observed;
a zinc rod was put in and the whole covered by a bell glass, over
water; in a few hours the operation had ceased, and there appeared 3480
grain measures of hydrogen gas generated; the dried antimony weighed
25½ grains, and the zinc had lost 29 grains. Now 3480 hydrogen require
1740 of oxygen = 2.3 grains in weight. But 29 zinc require 7 oxygen;
therefore the zinc must have got 4.7 oxygen from the antimony; that
is, 25.5 antimony were found united to 4.7 oxygen; this gives 100
antimony + 18.4 oxygen. I conclude then that the error is with Proust;
and this appears to be confirmed by the consideration that Proust
himself obtains only 86 oxide of antimony from 100 sulphuret, which
he allows to contain 74 antimony; now if 74 ∶ 12 ∷ 100 ∶ 17 nearly. I
am therefore inclined to adopt 18 for the oxygen which combines with
100 antimony to form the grey oxide. Whether this is the protoxide or
deutoxide may be disputed; and the facts known concerning the other
oxide or oxides will scarcely determine the case: but the proportions
of the muriate and sulphuret of antimony accord much better with the
former supposition. Now if 18 ∶ 100 ∷ 7 ∶ 39, for the weight of the
atom of antimony; I prefer the weight 40, deduced from the sulphuret,
as announced in VOL. 1, page 264.
The oxide which contains 30 on 100 must be 2 atoms of the deutoxide
and 1 of the protoxide united. What Berzelius calls the white oxide or
antimonious acid, may be 1 atom of each oxide united, containing 27
oxygen on the 100. The oxide supposed to contain 36 or 37 oxygen on
100, and which must be considered as the deutoxide, has not been proved
to exist separately. My efforts to procure it have failed as well as
those before mine: by treating muriate of antimony with oxymuriate of
lime I have obtained oxides of 30 on the 100, but never much higher.
Whenever a greater proportion of oxymuriate of lime is added, the smell
of the gas becomes permanent.
Antimony exposed to a red heat in a current of common air or oxygenous
gas takes fire, and white fumes arise formerly called _flowers of
antimony_; this oxide contains 27 or 30 oxygen on 100 metal.
Antimony thrown into red hot nitre is oxidized rapidly; the remaining
powder, washed in water, is found to be a compound of oxide of antimony
and potash. Berzelius calls the oxide the antimonic acid, and the salt
the _antimoniate of potash_. It consists, according to his experience,
of 100 acid and 26.5 potash. A similar salt formed between the
antimonious acid and potash is constituted of 100 acid and 30.5 potash.
19. _Oxide of tellurium._
We are chiefly indebted to Berzelius for the proportions in which
tellurium combines. He finds 100 tellurium unite to 24.8 oxygen. Also
that 201.5 tellurate of lead gave 157 sulphate of lead. This last
contains 116 oxide of lead, which must therefore have combined with
85.5 of the oxide of tellurium. Hence 97 oxide of lead would combine
with 71.5 oxide of tellurium = 57½ tellurium + 14 oxygen. Whether
this oxide of tellurium is the protoxide or deutoxide, is somewhat
uncertain. The atom of tellurium will weigh 57½ in the latter case,
but only 28 or 29 in the former. The analogy of the oxide to acids
favours the notion of a deutoxide; but the facility with which the
tellurium is volatilized by hydrogen is in favour of the lighter atom.
The oxide is a white powder; it is produced by dissolving the metal in
nitro-muriatic acid and precipitating by an alkali.
20. _Oxides of arsenic._
There are two distinct combinations of arsenic and oxygen; the one has
been long known as an article of commerce under the name of arsenic. It
is a white, brittle, glassy substance, obtained during the extraction
of certain metals from their ores. Its specific gravity is about 3.7.
According to Klaproth boiling water dissolves from 7 to 8 per cent.
of the oxide of arsenic; but on cooling it retains only about 3 per
cent.; and this I find is gradually deposited on the sides of the
vessel till it is reduced to 2 per cent. or less in cold weather, and
by some months standing. Water of 60° or under dissolves no more than
¼ per cent. of the oxide. At the temperature of about 400° the oxide
sublimes. This oxide combines with the alkalies, earths, and metallic
oxides somewhat as the acids do, but does not neutralize them, and in
other respects it is destitute of acid properties; as for instance, it
does not affect the colour tests. It is extremely poisonous.
The other oxide is obtained by treating either the white oxide or pure
metallic arsenic with nitric acid and heat. One hundred grains of
white oxide require two or three times their weight of nitric acid,
of 1.3, to oxidize them. The new oxide is produced in a liquid form;
from which the excess of nitric acid may be driven by a low red heat,
and the oxide is obtained pure in the form of a white opake glass,
which soon becomes liquid by attracting moisture from the atmosphere.
This oxide, discovered by Scheele, has all the properties of acids in
general, and is therefore denominated arsenic acid. When just fluid
by attracting moisture it has the sp. gravity 1.65 nearly. It is
represented as equally poisonous with the white oxide.
The proportions of the elements in these two oxides have been
investigated with considerable success. Proust finds the white oxide
constituted of 100 metal and 33 or 34 oxygen, and the second of 100
metal with 53 or 54 oxygen: with these results those of Rose and
Bucholz nearly agree. Thenard finds 100 + 34.6 for the white oxide,
and 100 + 56.25 for the acid: and Thomson 100 + 52.4 for the acid.
Berzelius however, infers from his recent experiments that the oxide
consists of 100 metal + 43.6 oxygen, and the acid of 100 + 71.3; these
last results I have little doubt are incorrect from my own experience.
It appears that when arsenic is oxidized by nitric acid, 100
parts yield from 152 to 156 of acid, dried in a low red heat. The
differences may in part be owing to the metal being partly oxidized
at the commencement of the operation. On this account I should suppose
55 or 56 to be the proper quantity of oxygen united to 100 metal to
form the acid. Proust and Thenard both found that 100 white oxide, when
converted into acid by nitric acid, gave 115 or 116. I have found the
same. Now if 116 ∶ 100 ∷ 156 ∶ 134; hence the white oxide of arsenic
must contain 100 metal to 34 oxygen, if the data be correct; or the
metal and oxygen are as 3 to 1 nearly. It is highly improbable that
any inferior oxide subsists, as no traces of such have been found, if
we disallow a conjecture of Berzelius on the subject. The white oxide
of arsenic must then be considered as the _protoxide_, and the atom of
arsenic must weigh 21 nearly, and that of the protoxide 28.
It is plain the other is not the _deutoxide_, as it does not contain
twice the oxygen of the protoxide; but as the proportion of oxygen
in it is to that of the protoxide, as 5 ∶ 3, it may be a compound
of 2 atoms of deutoxide, and 1 of protoxide; that is, it may be the
_superarseniate of arsenic_, if we consider the deutoxide as the acid,
and the protoxide as the base. According to this view, the compound
oxide, or _arsenic acid_ of Scheele, is constituted of two atoms of
the deutoxide, weighing 70, and 1 atom of the protoxide weighing 28,
together making 98, for the weight of an atom of arsenic acid, = 63
arsenic + 35 oxygen: and 100 arsenic take 55.5 oxygen to form the acid,
agreeably to the above recited experiments. Singular as this conclusion
may appear, the truth of it is put beyond doubt, I think, by the
following experiments.
I have repeatedly found that 28 parts of white oxide in solution are
sufficient to throw down 24 parts of lime, from lime water, so as to
produce 52 parts of arsenite of lime, and leave the water free from
both elements. This confirms the notion of the atom of protoxide
weighing 28.
If to 24 parts of lime dissolved in water we put 98 parts of dry
arsenic acid, the compound remains in solution, and is perfectly
neutral to the colour test, but so that the addition of a small
quantity of either ingredient disturbs the neutrality. If to this
solution 24 parts of lime dissolved in water be added, the compound
remains a limpid solution, but is very limy to the test. If to this
we put in like manner, 24 parts more of lime, the whole compound is
thrown down, and yields, when dried, 170 parts of arseniate of lime,
the liquid being now free from both elements. Here we see first, two
atoms of the deutoxide, neutralized by two atoms of base, namely, 1 of
arsenic oxide, and 1 of lime; but (second), when one atom more of lime
is added, an union of 2 deutoxide, and 3 of base is effected, which of
course is an alkaline salt; when (third) more of lime is added, the 2
deutoxide and the 1 protoxide each attach 1 of lime, and form a still
more alkaline salt, which being insoluble, is wholly thrown down, most
probably in a compound state of 98 parts arsenic acid, combined with 72
parts lime.
In like manner, I find that 42 parts of potash, 28 of soda, and 12 of
ammonia, severally neutralize 98 parts of arsenic acid.
1st. 24 lime + 32.7 arsenic acid = insoluble arseniate
2d. -- + 49 ------------ = soluble arseniate
3d. -- + 98 ------------ = neutral arseniate
It is a remarkable fact, that when neutral arseniate of potash
and nitrate of lead are mixed together to mutual saturation, the
precipitate is found to consist chiefly of arsenic acid and oxide of
lead, in proportion of 1 of acid to two of oxide, (that is, 98 ∶ 194,
or 100 ∶ 198); which does not differ much from the determination of
Berzelius.
I find however, only one fourth of the nitric acid in the residuary
liquid in a free state; which leads me to suspect that the precipitate
is a compound of subnitrate and arseniate of lead, in which the arsenic
acid and lead are in due proportion, or 98 acid, to 97 oxide. This
consideration may be properly resumed hereafter.
Hence we conclude, the atom of arsenic weighs 21 (and not 42, as at
page 264, VOL. 1), that of the protoxide of common white arsenic,
28; and that of arsenic acid = 98, being a compound of 2 atoms of
deutoxide, and 1 of protoxide. Or,
100 Arsenic + 33.3 oxygen = 133.3 protoxide
-- + 55.5 ---- = 155.5 arsenic acid
21. _Oxides of cobalt._
There are at least two oxides of cobalt, the one blue, the other black.
Authors differ as to the proportions of the elements. Proust states
the blue oxide to consist of 100 metal, and 19 or 20 oxygen, and the
black of 25 or 26 oxygen. Klaproth finds in the blue, 100 metal and 18
oxygen. But Rolhoff according to Berzelius, finds 100 metal and 27.3
oxygen in the blue oxide, and 40.9 in the black. I have taken some
pains to investigate these oxides, and have been able to satisfy myself
in a good degree, respecting their constitution. The blue or protoxide
consists of 100 metal and 19 oxygen, and the black oxide of 100 metal,
and 25 or 26, very nearly as Proust determined.
_Protoxide._ By repeated trials I have found, that if 37 parts of
metallic cobalt be treated with the due quantity of nitro-muriatic
acid, and a heat of 150°, a rapid solution takes place, and a
disengagement of pure nitrous gas; this being carefully collected, it
will be found to weigh 8 grains, and of course corresponds to 7 grains
of oxygen; hence 37 cobalt, unite to 7 oxygen, to form 44 of the blue
oxide; and as this is the only oxide that combines with acids, it must
be considered as the most simple or protoxide, being 1 atom of metal
(37), and 1 of oxygen (7). The estimation of the atom of cobalt at 50
or 60, (page 265), must therefore be corrected.
_Compound oxides._ When the blue oxide of cobalt is precipitated
from a solution, by an alkali or lime water, and oxymuriate of lime
is gradually dropped in, the precipitate changes colour rapidly; it
passes from blue to green and olive, thence to a dark bottle green,
and finally becomes black; oxygen gas is given out copiously when an
excess of oxymuriate of lime is used. I find the additional oxygen
requisite to convert the blue to the black oxide is what Proust states
it, namely, ⅓ of that necessary to form the blue; hence it must be
considered as a compound of 1 atom of oxygen and 3 of the protoxide.
Probably the other coloured oxides are 1 to 4, 1 to 5, &c. The
protoxide is blue when precipitated, but it is supposed to contain
water, or to be a hydrate; as it is dark grey when heated. The blue
oxide in a short time after precipitation being still under water,
changes to a yellowish or dead-leaf colour; which also appears to be a
hydrate of the protoxide, as it dissolves in acids without giving out
gas, and yields the blue oxide by an alkali. According to Proust, this
hydrate contains 20 or 21 per cent. water. If we suppose the blue to be
1 atom oxide, and 1 water, the yellow hydrate may be 1 water and 2 of
the proto-hydrate; or 88 oxide, and 24 water, which will be nearly 21
per cent. water.
The black oxide gives out oxygen gas by a red heat, and is reduced to
the grey oxide: it forms oxymuriatic acid, with muriatic acid, and the
protoxide remains in solution.
(See Tassaert.--An. de Chimie 28; Thenard, 42; and Proust, 60.)
22. _Oxides of manganese._
One of the oxides of manganese being a natural production, and
sometimes of great purity, and the metal not being obtainable without
skill and labour, it may be most convenient to adopt the inverse method
in our investigations; that is, to trace out the atom of metal from its
oxides.
_Native oxides of manganese._ Of late, I have met with excellent
specimens of this oxide; they are in masses of a grey, crystalline
appearance, sp. gr. 4, easily pulverizable into a greasy, shining, dark
grey powder. They are nearly pure oxide; but the more common sort is
blacker, and contains less or more of siliceous earth. Some specimens
are very harsh, require an iron mortar to pulverize them, and contain
50 or upwards per cent. of siliceous earth. Of the common sort when
pulverized, the black inclining to blue, is generally preferable to the
black inclining to brown. I have not observed any earthy carbonates
mixed with the oxide of manganese. Amongst various specimens I obtained
the following analyses.
Oxide. sand and insoluble
matter.
1. Grey, crystallized oxide 100 ----
2. Pulverized black oxide, from } 80 20
a bleacher, reputed good }
3. Another specimen, in the lump 77 23
4. A light brown oxide 47 53
5. A sparry oxide, abounding with } 27 73
flint; black brown when pulverized }
Some of the chemical characters of the native oxide of manganese are,
its giving oxygen gas by a red heat, its insolubility in nitric and
sulphuric acids, and its solubility in muriatic acid, but with the
accompanying circumstance of disengaging oxymuriatic acid.
All these facts shew that it is of the higher order of oxides, or
analogous to the brown and red oxides of lead.--The muriatic acid
solution abovementioned, contains an oxide of an inferior degree, which
is soluble in all acids, and which is the only oxide of manganese that
appears to be soluble in acids. If this be considered, (as it may with
the greatest probability), the protoxide, then it will appear from what
follows, that the common native manganese is the deutoxide, and that
there is an intermediate one, which contains a mean quantity of oxygen.
_Protoxide._ This may be obtained in solution with muriatic acid as
above, from the native oxide. Or the black oxide may be mixed with
sulphuric acid into a paste, and heated in an iron spoon to redness;
the mass being lixiviated, a solution of the protoxide in sulphuric
acid is obtained, generally with a slight excess of the acid; in this
process heat and the presence of sulphuric acid, expels the redundant
oxygen of the black oxide, and reduce it to the protoxide, which
hence becomes soluble. If in either of these solutions any oxide
of iron be present, whether from the manganese, or acquired during
the manipulation, it is easily discovered and separated, as I have
frequently found. Into any solution containing a mixture of the oxides
of manganese, the green oxide of iron, and the red oxide of iron, let
lime water be gradually poured; the red oxide of iron will be first
precipitated, next the green oxide, and lastly the oxide of manganese,
which may hence be separated from each other. Iron may also be
discovered and separated by carbonate of potash, which must be dropped
into the solution as long as any coloured precipitate appears; as soon
as it has subsided, the snow-white carbonate of manganese succeeds.
This white carbonate may be very conveniently used for obtaining
solutions of pure manganese in any of the acids.
When a solution of pure manganese is treated with lime water, or
ammonia, a light buff oxide, not much differing in appearance from the
yellow oxide of iron, is obtained. This oxide is soluble in all acids,
when recently precipitated; but, such is its avidity for oxygen, with
moderate agitation of the liquid it acquires oxygen and becomes brown,
when it ceases to be totally soluble; if dried in the air quickly, it
becomes brown and obtains considerable oxygen. The buff oxide recently
precipitated, is probably a hydrate; for, when the white carbonate of
manganese is heated gradually to red, the water and the acid are both
expelled, and a grey powder remains; this is quite black on the surface
of the mass, if exposed to the air during the process. Probably this
grey powder is the pure protoxide; it is soluble in acids, except the
black powder at the surface; perhaps but for the oxygen of the air, the
protoxide would be nearly white.
From its combinations with sulphuric and carbonic acids, I find the
weight of an atom of the protoxide to be 32, or the same as that of
iron. Dr. John, a German chemist, who seems to have investigated these
salts with more attention than any other person, has deduced nearly the
same results. (Annals of Philos. 2-172). He finds 33⅔ sulphuric acid +
31 oxide, and 34.2 carbonic acid + 55.8 oxide; that is, when reduced
to compare with my results, 34 sulphuric acid + 31.3 oxide, and 19.4
carbonic acid + 32 oxide. This near agreement may be considered as a
confirmation of the accuracy of both. Dr. John finds, as I have done,
three distinct oxides of manganese, the greyish green, the brown, and
the black. The first of these is the only one that combines with acids;
but we differ materially as to the quantity of oxygen in each. He found
manganese decompose water at the ordinary temperature; by oxidizing
the metal this way, 100 metal acquired 15 oxygen to constitute the
protoxide; according to this, 28 metal + 4 oxygen would make 32
protoxide; but this conclusion would be so contrary to all analogy,
that it cannot be admitted as satisfactory. The probability is, that
the manganese must have contained a little oxygen at the commencement
of the experiment. The general analogy of manganese to iron, lead, &c.
requires that 32 protoxide should contain 7 oxygen. If this be allowed,
we have the atom of manganese = 25, and not 40, (as at page 266, VOL.
1), the same as that of iron: and this conclusion is corroborated by
what follows.
2. _Intermediate or olive brown oxide._ This may be formed by combining
oxygen directly with the buff or protoxide recently precipitated,
and still remaining in the liquor; simple agitation in oxygenous gas
or common air for a few minutes, is all that is requisite. Or it may
be instantly formed by treating the same moist protoxide with liquid
oxymuriate of lime. Or it may be had by exposing the purest black oxide
to a bright red heat for some time, when it will lose 9 or 10 per cent.
and there will remain the olive brown oxide.
To find the proportion of oxygen absorbed, I precipitated 3.2 grains
of the protoxide by lime water; the liquid containing the oxide was
put into a well stoppered bottle of oxygen gas; on agitation the oxide
changed colour fast, from buff to brown; in a short time it absorbed
260 grain measures of gas = .35 of a grain in weight, and then ceased
to absorb. In another experiment, 3.2 grains of precipitated protoxide,
took 100 measures of a solution of oxymuriate of lime, containing .35
per cent. of oxygen, (that is, 1.45 oxymuriatic acid). Hence as 32
take 3.5, 64 must take 7; which shews the brown oxide to be a compound
of 1 atom of oxygen, and 2 of the protoxide.
The characters of this oxide are, its olive brown colour, its
insolubility in nitric and sulphuric acids, without heat or
deoxidation, and its solubility in muriatic acid after the evolution of
oxymuriatic acid. By long exposure to the air, it is gradually changed,
in all probability into the black oxide.
3. _Deutoxide._ In order to determine the quantity of oxygen deducible
from the purest native oxide of manganese, to convert it into
protoxide, I have successfully adopted the two following methods. 1st.
Let 39 or 40 grains of the oxide be mixed with 60 common salt; to this
add 80 grains of water, and 120 grains weight of strong sulphuric
acid, in a gas bottle. The heat must be gradually raised to boiling,
and the oxymuriatic acid gas may be received in a quart of lime water.
This will be found sufficient to convert 800 measures of test green
sulphate of iron (1.156) into red; that is, it will produce 29 grains
of oxymuriatic acid, which will cause 7 grains of oxygen, to unite to
the green oxide of iron. Now 100 measures of 1.156 sulphate, according
to some recent experiments of mine, contain 8 grains of green oxide,
(I estimated the sp. gr. of test sulphate, heretofore at 1.149);
hence 800 contain 64 oxide, and these require just 7 grains of oxygen
to be united to them, to form the red oxide, as has been shewn, page
34. In the above experiment, the 39 grains of oxide, will be found to
vanish or be dissolved, if pure, and to yield 32 grains of protoxide,
making up with the 7 grains of oxygen, the original weight. Hence we
have 39 grains of the oxide resolved into 32 protoxide, and 7 oxygen.
If then we allow 32 protoxide, to contain 7 oxygen, it appears that
39 grains of the native oxide, consists of 1 atom manganese (25), and
two atoms of oxygen (14); or it is the deutoxide of the metal. 2d. A
more direct and expeditious method, of transferring the oxygen from
the manganese to the iron, is as follows: Let 39 grains of pure grey
shining oxide, be mixed with 800 of test green sulphate of iron; to
this mixture let 25 or 30 grain measures of strong sulphuric acid be
added: after stirring the mixture for 5 minutes, the oxide of manganese
will be completely dissolved, and, on precipitating the oxide of iron
gradually, by lime water, it will be found to be wholly _yellow_ or
buff; shewing that 7 grains of oxygen have been transferred from the
oxide of manganese to that of iron.--If more green sulphate of iron
be used, then the surplus of the oxide will be thrown down green; the
order of precipitation being the yellow oxide of iron, the green oxide
of iron, and lastly, the yellow or buff oxide of manganese, as has been
stated. This affords an easy and elegant method of appreciating the
different oxides of manganese of commerce; and it was in this mode, the
valuations of the specimens in the above table were made.
The proportions of the three oxides are then as under:
Manganese Oxygen
Protoxide 100 + 28 -- buff; soluble in acids.
Intermediate oxide -- + 42 -- brown; insoluble.
Deutoxide -- + 56 -- black; insoluble.
It may be proper to subjoin the results of others, who have
investigated the oxides of manganese. Bergman finds 3 oxides,
containing 100 metal + 25, 35, and 66.6 oxygen; Dr. John finds 3
oxides, containing 100 metal + 15, 25, and 40 oxygen: Berzelius finds
5 oxides, containing 100 metal + 7, 14, 28, 42, and 56 oxygen; and
Davy finds 2 oxides, containing 100 metal + 26.6, and 39.9 oxygen,
respectively.
23. _Oxides of chromium._
There appear to be at least two oxides of chromium, one or other of
which is found in combination with the oxides of lead or iron, but
hitherto so very sparingly that few chemists have had an opportunity of
investigating the proportions of chrome and oxygen, in the oxides of
chromium. The chief sources for information on this subject, are essays
by Vauquelin, An. de Chimie, VOL. 25 and 70; by Tassaert, _ibid._ 31;
by Mussin Puschin, _ibid._ 32; by Godon, _ibid._ 53; by Laugier _ibid._
78, and by Berzelius, Annal. of Philosophy, 3.
The oxides of chromium, as might be supposed, are distinguished for the
colours which they possess and impart to the compounds into which they
enter. One of the oxides is green; it gives colour to the emerald. The
other is yellow, dissolved in water, but deep red when crystallized,
and possesses the characters of an acid; it unites with alkalies,
earths, and metallic oxides; it was first found in Siberia, in
combination with the oxide of lead, a salt now denominated _chromate_
of lead, of a splendid yellow colour, inclining to orange or red.
Since then, the chromate of iron, has been found in France, America,
and Siberia, with a prospect of greater abundance.
In order to investigate the weight of the atom of chromic acid, it is
necessary to attend to such of the chromates as have been carefully
examined. The chromates of potash, barytes, lead, iron, and mercury,
are those with which we are best acquainted.
Vauquelin has given us the components of the native chromate of lead
by analysis, and those of the artificial chromate by synthesis; the
results do not accord very nearly: for, according to the analysis
corrected by the modern science,
Chromate of lead = 62 acid + 97 oxide
By synth. chromate of lead = 57½ -- + 97 --
Berzelius however, has more lately given us the results of his
experience, both analytical, and synthetical; and he finds both to give
chromate of lead nearly = 44 acid + 97 oxide.
Chromate of barytes (Vauq.) = 47.8 acid + 68 barytes
Ditto (Berz.) = 44 -- + 68 --
Native chromate of iron (Vauq.) = 45 acid + 35½ oxide
Ditto (Laugier) = 55 -- + 35½ --
Having received a small portion of chromate of potash in solution,
from a chemical friend (J. Sims), I endeavoured to satisfy myself, as
far as my materials would go, as to the nature and proportions of the
chromates. The solution was of the sp. gr. 1.061, and consequently in
100 measures contained nearly 6.7 grains of chromic acid and potash,
&c.--The liquid was a beautiful yellow; it was alkaline by the colour
test. By the usual tests, I had reason to believe, that the solution
contained as under per cent.--namely,
2.2 gr. chromic acid
2. potash
.8 uncomb. potash
1.4 carb. potash
.3 sulphate of potash
---
6.7
With this liquid neutralized by nitric acid, I formed the chromates of
lead, barytes, iron, and mercury; and I am inclined to believe these
salts are nearly constituted as under:
Neutral chromate of potash 46 acid + 42 potash
-- -- of barytes 46 -- + 68 barytes
-- -- of lead 46 -- + 97 oxide
-- -- of iron 46 -- + 32 oxide (black)
-- -- of mercury 46 -- + 174 oxide (black)
According to these results, the atom of chromic acid weighs 46; it is
made 44 by the results of Berzelius, and from 45 to 62 by those of
Vauquelin; I would not be understood to place great confidence in the
above results of mine, though I am persuaded they will be found good
approximations.
Is the chromic acid the deutoxide, or the tritoxide of chromium?
The determination will evidently be affected by the question, how much
oxygen must be abstracted from the chromic acid to reduce it to the
green oxide. Vauquelin finds 46 acid to lose 6½ oxygen, and Berzelius
10½, when converted into green oxide by heat. From the former of these,
one would infer chrome to be 32, the green or protoxide of chrome to
be 39, and the acid or deutoxide 46: from the latter, chrome = 25,
protoxide = 32 (unknown), the green oxide = 1 protoxide and 1 deutoxide
united [= 71 = 50 chrome + 21 oxygen = (25 chrome + 10½ oxygen) × 2 =
35½ × 2] the deutoxide = 39, and the tritoxide or chromic acid = 46.
I have not had an opportunity to perform any experiment that appears
to me decisive as to the accuracy of one or other of these views; but
shall make a few remarks relative to them.
The green oxide being the most prominent compound next to the chromic
acid, being commonly produced from it by any deoxidizing process, being
the lowest oxide known, and combining with acids, is on these accounts
entitled to the consideration of the protoxide; indeed there does not
seem an instance where the protoxide of a metal is unknown, whilst the
deutoxide and compound oxides are known. There is however, another
oxide observed by Vauquelin and by Berzelius, which is obtained by
heating the nitrate, or combination of nitric acid and the green oxide,
to dryness and expelling the acid; this oxide is brown, and gives
oxymuriatic acid when treated with muriatic acid; on this account it
would seem to be intermediate between the green oxide and the chromic
acid; it is probably a combination of the two, or the _chromate of
chromium_. On the other view however, it must be considered as the
deutoxide. What corroborates the notion of the green oxide being 39, is
the fact which I have observed, of 46 parts of chromic acid combining
with 64 of the green oxide of iron to form 110 of chromate of iron; in
this combination the oxide of iron may be said to borrow 1 atom of
oxygen from the chromic acid, and the compound may then be considered
as the union of the green oxide of chrome, and the red oxide of iron.
When this precipitate is subjected to the action of muriatic acid, a
green solution is obtained containing the oxide of chrome, and red
oxide of iron is precipitated, as Vauquelin has observed. To form the
above chromate (or rather subchromate) of iron, let a given portion
of neutral chromate of potash be treated with green sulphate of iron,
and lime water be added, sufficient to saturate the sulphuric acid, a
brown red precipitate is obtained; more sulphate and lime water must be
gradually added to the clear liquid till the precipitate become green,
when the proportions will be found as above stated. This artificial
compound seems a subchromate; whereas the native compound seems to be a
chromate. That there is some uncertainty in decomposing a chromate by
heat with a view to obtain the green oxide, I have reason to suspect
from having decomposed 5⅓ grains of chromate of mercury by a moderate
red heat; this compound contained 1.1 chromic acid, and it yielded only
.6 of green oxide, whereas it should have been .9 or .8 at least.
Upon the whole I think the evidence is in favour of the opinion that
the atom of chrome is 32, the green or protoxide 39, and the deutoxide
or chromic acid is 46.
24. _Oxides of uranium._
There appear to be two oxides of uranium from the experiments of
Klaproth, Bucholz, and Vauquelin; but the proportions of metal and
oxygen have not been very nearly ascertained, from the great scarcity
of the minerals containing this metal. (Vid. Bucholz, An. de Chimie,
56--142. Vauquelin, ibid. 68--277; or Nicholson’s Journ. 25--69). The
oxides are obtained by precipitation from solutions of the minerals
in the nitric or muriatic acid, the foreign substances being first
separated.
The protoxide of uranium precipitates dark bottle green by caustic
alkalies, and forms crystallizable salts with acids; the other,
probably the deutoxide, precipitates orange yellow, and forms
uncrystallizable salts with acids; in these respects the oxides bear a
near resemblance to those of iron.
Bucholz estimates the yellow oxide at 100 metal + from 25 to 32 oxygen;
as it yields oxymuriatic acid when treated with muriatic, it is most
likely to be the deutoxide; now if we take 28 for the oxygen combined
with 100 metal, the protoxide must consist of 100 metal + 14 oxygen, or
of 50 metal + 7 oxygen, and the atom of uranium = 50. From his account
of the sulphate and nitrate of uranium the weight of the atom might be
inferred to be double of the above or 100. These different conclusions
can only be elucidated by future experiments.
25. _Oxides of molybdenum._
The latest and as it should seem most accurate experiments on
the oxides of molybdenum were made by Bucholz. (Vid. Nicholson’s
Journal, 20, p. 121). There appear to be 3 oxides or combinations
of molybdenum and oxygen, namely, the _brown_, the _blue_, and the
_white_ or _yellow_. The two last have the character of acids, and
none of them seem to form salts with acids, like oxides in general.
Bucholz ascertained the above gradation, and that the white oxide or
molybdic acid contains ⅓ of its weight of oxygen; (which has since
been corroborated by Berzelius); he also found that the blue was best
formed by mixing, triturating, and boiling in water 3 parts of brown
oxide, and 4 of white, or one of metal, and two of acid; and that it
has acid qualities as well as the white. Bucholz also found 3 parts
of liquid ammonia of the sp. gr. .97 dissolve 1 of molybdic acid; now
3 parts of ammonia = .186 real (VOL. 1, p. 422); and 1 ∶ .186 ∷ 64 ∶
12, the quantity of ammonia usually saturated by one atom of acid;
and Berzelius found 100 molybdic acid saturate 155 oxide of lead, or
63 acid to 97 oxide. The native sulphuret of molybdenum (the state in
which this metal is usually found) was analyzed by Bucholz and found to
consist of 60 metal and 40 sulphur.
The molybdic acid may be obtained by roasting the sulphuret in a
crucible and stirring it frequently; the sulphur in great part escapes
in the form of sulphurous acid and the metal becomes oxidated:
carbonate of soda in solution may be added to the residuum as long as
any effervescence is observed; molybdate of soda remains in solution
and the acid may be precipitated by nitric acid. The brown oxide is
best obtained by heating molybdate of ammonia to red; the ammonia and
part of the oxygen are expelled, and the brown oxide remains.
There are two views with which the preceding results may be reconciled;
namely, 1st. supposing the atom of molybdenum to weigh 21; and 2d, by
supposing it to weigh 42 or twice that number. In the first case the
brown oxide will weigh 24½ (49) being supposed 2 atoms of metal and 1
of oxygen, the blue or protoxide will weigh 28, and the white oxide
or molybdic acid will weigh 63, being a compound of the protoxide and
deutoxide, molybdena or native sulphuret will then be as usual, the
protosulphuret, consisting of 21 metal and 14 sulphur, or 60 metal
and 40 sulphur. In the 2d. case the brown or protoxide will weigh 49,
the blue or deutoxide 56, and the acid or tritoxide 63. The native
sulphuret, molybdena, must in this view be the deutosulphuret, or 42
metal and 28 sulphur.
The former of these views exhibits the oxides somewhat complicated,
but agrees well with the sulphuret; the latter shews the oxides in a
more regular train, but does not appear so probable from the sulphuret;
besides, the notion of a metallic tritoxide is rather singular,
especially in a metal that is rarely if ever found in combination
with oxygen. Upon the whole I prefer the former view; but it must be
considered as problematical only. The atom of 60 (see page 267 VOL. 1)
must doubtless be erroneous.
26. _Oxides of tungsten._
From the experiments of D’Elhuiarts, Bucholz[13] and Berzelius[14] it
seems very probable that the tungstic acid is composed of about 100
metal + 25 oxygen. It is a _yellow_ powder of the sp. gr. 6.12, and is
best obtained from the native tungstate of lime (a scarce mineral).
One part tungstate of lime and four of carbonate of potash are fused
together, dissolved in water, and then the tungstic acid may be
precipitated by nitric acid. There is an inferior oxide that is black
or dark brown; Berzelius reduced the yellow oxide to a flea-brown
colour, by sending a current of hydrogen gas through it in a glass tube
heated red hot. 100 parts of this oxide burnt be 107 yellow oxide.
Hence 100 metal must combine with about 16½ or 17 oxygen to form this
oxide, which is ⅔ of that in the yellow or tungstic acid.--Upon the
whole it does not seem improbable, considering the great sp. gravity
of this metal, that it forms three oxides and that the acid or yellow
oxide is the 3d. Hence the atom of tungsten must be 84, that of the
protoxide 91, the deutoxide 98, and the tritoxide or tungstic acid 105.
The native tungstate of lime, if pure, according to this would be 81.4
acid + 18.6 lime, which is not far from Klaproth’s analysis; he having
found 18.7 lime in one specimen; nor from that of Berzelius, he having
found 80.4 tungstic acid and 19.4 lime in 99.8 tungstate of lime.[15]
[Footnote 13: An. of Philos. 6--198]
[Footnote 14: An. of Philos. 3-244]
[Footnote 15: An. of Philos. 8--237]
There is another view however, which would accord with the experiments
and perhaps will be found preferable in other respects; that is, to
suppose the tungstic acid to be composed of 1 atom deutoxide and 1 atom
protoxide united; in this case the atom of tungsten = 42, that of the
protoxide = 49, that of the deutoxide = 56, and the tungstic acid = 105
as before.
27. _Oxides of titanium._
Nothing certain is known respecting the oxides of titanium. An
observation of Richter, quoted by Berzelius (An. of Philos. 3--251), if
it could be relied upon, furnishes an important fact, namely, that a
solution of muriate of titanium containing 84.4 oxide, gave 150 muriate
of silver. Now 150 muriate of silver contain 28 acid; hence 28 acid
must have combined with 84.4 oxide; but if 28 ∶ 84.4 ∷ 22 ∶ 66 nearly
for the weight of an atom of the oxide. This would indicate 59 for an
atom of the metal.
28. _Oxides of columbium._
The white oxide or acid of columbium is found in combination with the
oxides of iron and manganese in proportion nearly as 4 of the acid to
1 of the aggregate oxides. The two minerals, columbite and tantalite,
though yielding these substances nearly in the same proportions, are
found to differ remarkably in specific gravity, the former being
about 5.9 and the latter about 7.9. Dr. Wollaston concludes however,
from the agreement of the white oxides extracted, that they must be
the same. The white oxide of columbium is insoluble in the mineral
acids; it unites with potash by fusion, and may be precipitated by
most acids. Some of the vegetable acids, the oxalic, the tartaric, and
the citric dissolve the white oxide. When the alkaline solution of
columbium previously neutralized by an acid is treated with infusion
of galls, an orange precipitate is produced which is characteristic
of columbium. Nothing certain has been determined respecting the
proportions of metal and oxygen; but from the great proportion of the
columbic acid found with the oxides of iron and manganese, together
with the great sp. gravity of the compound, one may pretty clearly
infer the great weight of the atom of columbium. Supposing the white
oxide or acid to consist of 1 atom metal + 3 oxygen and that the
columbite is formed by 1 atom of acid to 1 of oxide, we should have
128 acid + 32 oxide. This would give 107 for the weight of an atom of
metal, and 128 for that of the tritoxide or columbic acid; but it is
unnecessary to dwell upon such conjectures.
In a recent memoir of Messrs. Gahn, Berzelius, and Eggertz (An. de
Chimie, Octo. 1816), it is maintained as probable that there is only
one oxide of columbium or tantalum, and that 100 metal take 5.485
oxygen, or 121 metal take 7 oxygen. If this be correct, the atom of
columbium must be 121 and the protoxide 128.
(See also An. de Chimie, 43--271; Philos. Trans. 1802; Nichols. Journ.
2--129; ibid. 3--251; ibid. 25--23).
29. _Oxides of cerium._
The mineral cerite is of the sp. gr. 4.53, and constituted of 50 or 60
per cent. of oxide of cerium, with silex, lime, and iron. This mineral
being calcined and dissolved in nitro-muriatic acid, the solution is
to be neutralized by caustic potash, and then treated with tartrate of
potash. The precipitate, well washed and afterwards calcined, is pure
oxide of cerium. This oxide, which is white, when calcined in the open
air becomes red and acquires more oxygen. These oxides, particularly
the white, are soluble in most acids; the red oxide with muriatic acid
gives oxymuriatic acid.
The experiments hitherto made on this subject scarcely enable us to
decide respecting the proportions of metal and oxygen, nor the relative
weights of these oxides.
Both Vauquelin[16] and Hisinger[17] agree that the protocarbonate
of cerium, when exposed to a red heat, yields 57 or 58 oxide, which
the former says is the red oxide, being changed by the calcination.
Hisinger finds the percarbonate to consist of 36.2 acid and 63.8
oxide: also that the muriate of cerium consists of 100 acid and 197.5
oxide; but Vauquelin remarks that the sulphate, nitrate, and muriate
of cerium are always more or less acid, however dried; and he found
the protoxalate of cerium to yield 45.6 red oxide by calcination, on
a mean of 3 experiments not much differing from each other. Supposing
all these facts accurate, they may be reconciled by a few suppositions
by no means improbable. Let the atom of cerium be 22, the protoxide
29, and the red oxide 32½ (that is, 1 oxy. + 2 protox. = 65); and let
the protocarbonate be 1 atom of acid, 1 of oxide, and 1 of water; the
percarbonate, 1 acid 1 oxide; the oxalate, 1 acid (40) and 1 oxide; and
the muriate, saturated with base, 3 oxide and 2 acid. Then it will be
found that,
[Footnote 16: An. de Chimie, 54--28]
[Footnote 17: An. of Philos.--4--356]
The decomposed protocarbonate will yield 57.5 red oxide;
The decomposed percarbonate will yield, 36.7 acid, 63.3 oxide;
The decomposed oxalate will yield 47 red oxide; and
The muriate will yield 100 acid (22), and 197.7 oxide.
All of which agree very nearly with the results above obtained.
Hence it appears to me very probable that the several atoms of the
metal and the oxides are as stated above; and that,
100 cerium + 31.8 oxygen = 131.8 protoxide, white.
---------- + 47.7 ------ = 147.7 intermediate, red.
Hisinsger, from some of the same data united to other hypothetical
facts than those assumed above, deduces the two oxides very different;
viz. 100 metal + 17.4 oxygen for the protoxide, and 100 + 26.1 for the
peroxide.