Edmund Knecht.

A manual of dyeing: for the use of practical dyers, manufacturers, students, and all interested in the art of dyeing online

. (page 40 of 53)
Font size
QR-code for this ebook

well-saturated silk is wrung out, and the excess of liquor returned to the bath ;
t'le silk is then rinsed in running water to precipitate stannic hydroxide in the
fibre, while a soluble acid salt is removed by washing. Frequently a cold
solution of soda is used for the fixation. The weight of the silk can be in-
creased up to 25 per cent, by repeated operations. The solution of stannic
chloride must not be too strong, since the silk shrinks perceptibly in a solution
of the salt at 50° Tw., and begins to dissolve in a liquor at 100° Tw. Repeated
Boapings at the boil are necessary to restore the natural feel to the silk, and it
is always prone to deteriorate after some time under the influence of light.
The tin has also an injurious effect on some of the colours which are afterwards
applied. If these colours are not dulled too much by such treatment the silk
is often weighted first with stannic chloride, and, subsequently, with tannin
(tannic acid, sumach, or catechu) in order to prevent the subsequent deteriora-
tion of the fibre and to increase its weight and volume.

More recently this method has been improved by the use of phosphate of
soda, the silk, after steeping in the stannic chloride and rinsing in water,
being worked thirty minutes at 50° to 60° C. and thirty minutes at the boil in
a solution of the phosphate, and then well rinsed. The treatment in stannic
chloride and phosphate of soda is repeated several times, sufficient sulphuric
acid being added to the last bath of phosphate to liberate one-third of tho
phosphoric acid employed. This treatment is less detrimental to the silk
than the former, and yields a higher weighting. As the subsequent tanning
is unnecessary, the white colour, the gloss, and the feel of the silk are much
better preserved.

A further improvement was patented by J. H. Neuhaus' successor of
* See also the very exact researches of P. Heermann, I.e., p. 238.



TITANIUM.



279



Crefeld, by the application of sodium silicate, which yields a weighting of 50 to
60 per cent., and even 100 to 120 per cent., above "pari" without injuring the
gloss and feel of the fibre, although, after some time, a considerable weakening
of the fibre is sometimes observed. Neuhaus treats the silk for one hour in
stannic chloride (42° to 52° Tw.), and after squeezing and rinsing for one-half
to one hour in a warm bath of soluble phosphates — e-g., sodium phosphate
(4° to 7° Tw.) — the silk is then again rinsed, worked for one-half to one hour in
a warm bath of sodium silicate (4" to 7° Tw.), and eventually rinsed. The silk
is weighted to 100 to 120 per cent, above "pari" by five passages through
stannic chloride, sodium phosphate, and silicate. The treatment with silicate
renders the silk somewhat hard, and, therefore, it is usually dispensed with
after the first, and even the later, treatments with phosphate, and applied only
for the third and following ones. Some of the treatments with phosphate are
occasionally omitted. Gnehm and Baenziger,* who studied this process very
thoroughly, give the follow^ing scheme : — Tin, phosphate, tin, phosphate, tin,
phosphate, tin, phosphate, tin, silicate, tin, silicate, whereby a weighting of 120
to 150 per cent, above "pari" was attained. E. C Puller found that the
weighting is increased by 19 per cent, by treating the silk between the phos-
phate- and the silicate-baths in aluminium sulphate (15° Tw.). Other metallic
salts have been recommended for the same purpose.

The baths of stannic chloride become strongly acid by continued use,
more stannic oxide than acid being taken up by the silk. For restoring their
original strength, in addition to stannic chloride, some ammonia must be added
to the baths to keep them in good condition. The quantity of ammonia
required is determined by a preliminary test. After some time the liquor will
contain too much ammonium chloride, and must be let oif; the tin is recovered
by precipitating with lime and reducing to metal. f

Excessive weightin'^ of silk by the tin-phosphate-silicate process is liable to
bring about serious faults in the goods. Thus, silk heavily weighted by this
process has frequently been found to become quite tender by a comparatively
short exposure to direct sunlight. On the other hand, reddish-coloured spots
often appear in the pieces, but are sometimes only found after the latter have
been stored for months. Where these spots have formed the silk is usually
tender. Gnehm, Roth, and Thomann X attributed their formation to the
action of perspiration. Later on, Sisley§ showed that the only constituent of
the latter which had an injurious action was the salt. More recently, O.
]Meister|| pointed out that the destruction of the fibre was due to acti^'e
chlorine produced by the catalytic action of copper, w^hich was always found
to be present, though in very small quantities, and gets into the goods by
careless handling during spinning and weaving. This author has suggested
padding the goods in a weak solution of ammonium sulphocyanide as a pre-
ventive. Though this treatment has been found effective to a considerable
extent, it is not infallible. Still more recently the use of thio-ureaU and its
salts and derivatives has been patented for the same purpose.

It is said that silk which has been weighted by the tin-phosphate process,
and has subsequently become tender, regains its strength on being treated
with hydrofiuoric acid.

TITANIUM, Ti = 481.

This metal, which has until comparatively recently been classed among the
rarer elements, occurs in nature both widely distributed and in large quantities.

* Joum. Soc. Dyem and Col., 1897, p. 40. + Ibid., 1889, p. 159.

t Ibid., 1902, p. 2.^0. § Ibid., 190-', p. 276.

II Ibid., 1905, p. 192. II Ibid., 1907, p. 51.



2 8o A MANUAL OF DYEING.

The metal itself is difficult to prepare in the pure state, and has no technical
intex'est. It yields, altogether, four oxides, and of these the salts of two only
— viz., Ti.^Og and TiO^ — are articles of commerce. The sesquioxide Ti^O^ is
obtained in the form of its hydrate by the addition of a caustic alkali to
titanous sulphate as a black precij)itate which readily absorbs oxygen from the
air, yielding the white TiOo. So great is its affinity for oxygen that even at
the ordinary temperature, but more readily on warming, it decomposes water
with liberation of hydrogen — Ti^Og + H^O = 2Ti02 + Ho- The sesquioxide
and its salts are very powerful reducing agents.

Titanous chloride * (Titanium trichloride or sesquichloride), TiClg + GH.^O.
This salt can be obtained by the reduction of titanic chloride by means of zinc,
tin, aluminium, &c., or by electrolysis. It crystallises from its very concen
trated solution in violet crystals which rapidly absorb oxygen from the air,
even when dry ; the solid is, consequently, not a commercial article. Titanous
chloride is sold as a violet-coloured solution containing 20 per cent. TiClg, along
with an excess of free hydrochloric acid. The solution can bo diluted with
Avater to any extent as long as the latter does not contain any temporary hard-
ness or alkalinity. In case only hard water should be available, the titanous
chloride shou.ld be mixed, before being diluted, with an equal volume of
hydrochloric acid.

Titanous sulphate, Ti2(SO^)3, can be obtained in solution by the electrolytic
reduction of titanic sulphate, and is sold like the chloride, as a 20 per cent,
solution. With sodium sulphate it forms double salts, one of which can be
obtained by salting out its deep purple black solution at the boil. It has the
composition Ti2(S04)3 . Na^SO^ . 5H2O, and crystallises in lilac-coloured cubes,
readily soluble in water. A more hydrated form, having the composition
Ti.,(SOj).^ . NaoSO^ . 12H.,0, forms much larger crystals, and is much less stable
in the air.

Titanous fluoride can be obtained by the reduction of titanic fluoride, and
dissolves in water with a violet colour, while its double compound with sodium
fluoride is green. The oxalate and the double compound titanous potassium
oxalate are brown and yellow in colour respectively ; the latter is very
sparingly soluble in water.

The titanous salts ai"e characterised by their powerful reducing properties ;
they are, in fact, the most powerful acid-reducing agent.s that are technically
available. Titanous chloride reduces ferric salts quantitatively in the cold,
and, on boiling, acts similarly on nitro- and nitroso-compounds, azo dyes, and
most of the colouring matters which yield leuco-compounds. In view of its
powerful reducing action, it is noteworthy that it does not reduce mercuric
chloride in the cold. Titanous sulphate behaves in most cases like the
chloride, but difiers from this in its behaviour towai'ds copper sulphate, from
which it throws down the whole of the copper as metal ; whereas, in the case
of the chloride, only a portion of the metal is thrown down, the reaction
being apparently a reversible one. The reaction of the sulphate with copper
sulphate is sufficiently delicate to serve as a means of detecting the presence of
copper in the ash of dyed fabrics.

Titanic sulphate, T'li^O^.^ + SHoO, is formed by dissolving titanic hydrate
in cold sul[)huric acid, but is not easily obtained in a crystalline form. The
double compound with sodium sulphate, having the formula Ti(80^)o -I- NaoSO^ +
2H.,0, is, however, readily obtained in the form of well-defined needle-shaped
crystals, and is a commercial article. It dissolves in a little over a third of
its weight of cold water, but the solution only takes place slowly. If the water

* The true titanous chloride, TiCU, corresponding to stannous chloride can onlj' be
obtained with difficulty — e.g., by passing hydrogen over the trichloride heated to rednesa
in a porcelain tube. It has no technical importance.



TITANIUM. 281

is heated the compound decomposes, and then only goes into solution after
standing in the cold for a very long time.

Titanic potassium oxalate, TiOC^H^ + K.^C^O^ + H,,0, forms well-defined
j;rystals, readily soluble in hot watei", and is the most stable of the crystallised
titanic salts. It is a commercial article, and finds considerable application in
the leather industry.

Titanium tanno-oxalate is a solution of titanium tannate in oxalic acid. It
is of a deep brown colour, and finds application in the dyeing of chrome tanned
an'l alumed leathers, and also of cotton.

The titanic salts are characterised by their behaviour towards peroxide of
hydrogen and towards tannic acid, ^\^ith the former they yield an intense
orange to yellow colouration, the reaction constituting a very delicate test for
either titanic compounds or peroxide of hydrogen. With tannic acid insoluble
titanic tannate is produced, which also has an orange colour.



APPLICATION OF THE TITANIUM COMPOUNDS TO THE
TEXTILE FIBRES.

Cotton and Linen. — Cotton may be mordanted with titanium in a variety
of ways. The simplest method, though not the most effective, is to run the
goods through a solution of titanic sodium sulphate or of the double oxalate,
and then thi'ough soda. Better results are obtained by a process which is
based upon the dissociation of the titanic chloride (or sulphate) in the fibre.
To this end the cotton is first dyed manganese bronze, preferably by steeping
in tannic acid, and then treating in a solution containing 1 to 2 grms. perman-
ganate of potash and a like amount of magnesium sulphate per litre. The
cotton is then transferred to a bath of titanous sulphate, when the manganese
bronze is almost instantly discharged and an equivalent amount of titanium is
fixed on the fibre. Should the cotton now possess a yellow colour, this will be
due to the tannic acid not having been completely oxidised by the permanganate.
For very light shades it is not necessary to use tannic acid, the unbleached
cotton being treated directly with permanganate, and then with titanous
sulphate. Bleaching and mordanting are thus eifected simultaneously. In
place of using manganese bronze for the precipitation in the fibre of titanic
hydrate, iron-buff, dyed in the ordinary way, can be used. It is thus possible
to so load the fibre with titanic hydrate that it burns much less readily than
ordinary cotton.

According to another process, patented by J. Barnes in 1896, cotton can be
mordanted by steeping it in a solution of tanno-oxalate of titanium of 1° to 2°
Tw. for some minutes, then wringing and transferring to a hot solution of
common salt. Titanium tannate is thus fixed on the fibre. This process is
more rapid and economical than first mordanting with tannic acid and then
passing through titanic sulphate. In either case, however, titanium tannate is
most suitable as a mordant for basic colours. With mordant colours it does
not give satisfactory results.

l^aw linen treated for a short time in a hot bath of titanous chloride
acquires the shade of orange-brown characteristic of "Brown Holland."

Wool. — According to Hummel,* titanium does not possess any general
advantages over chromium and aluminium, though, in some particular cases, it
gives distinctly superior results. f Dyeing is commenced with the mordant
colour and a little acetic acid, the bath is raised to the boil in the course of

* Joiim. Soc. Di/ers and Col., 15)04, p. 65.
tSee also J. Barnes, ibid., 189(3, p. 174.



25 2 A MANUAL OF DYEING.

half an hour, and, after boiHng for half an hoiu-, addition is made of 15 to 20
per cent, of the mordant solution (solution of titanium sodium sulphate con-
taining 4 per cent. TiOg) and 7| to 10 per cent, oxalic acid, after which boiling
is continued for twenty to thirty minutes.

Silk. — According to G. H. Hurst,* silk can be mordanted by steeping for
three to four houi's in a 5 per cent, solution of titanium potassium oxalate or
titanium sodium sulphate, and then through a 5 per cent, solution of calcium
acetate. Or the silk is first steeped for three to four hours in a 5 per cent,
solution of titanous chloride, and then in a 5 per cent, solution of sodium
phosphate. The tanno-oxalate may also be used for the purpose, the silk
acquiring the characteristic yellow colour of this compound. The mode of
procedure is similar to the others, the silk being steeped for three to four hours
in a 5 per cent, solution of the tanno-oxalate, after which it is washed.

The colours obtained with mordant dyes on material mordanted with
titanium are generally intermediate in shade between those obtained with the
same dyestuff on chromium and on aluminium mordant. Especially good
results are obtained on titanium mordanted cotton with Alizarin orange,
Alizarin yellow (M.L.B.), Coerulein, &c. ; on wool, with these colours, as also
with Alizarin cyanine green (Bayer), Anthracene blue (B.A.S.F.), Brilliant
Alizarin blue (Bayer), and Gallocyanine. According to Hummel, logwood
yields on titanium mordant a black, which is much more dead than that
obtained on chromium mordant. On silk, perhaps the most noteworthy result
recorded by Hurst is the yellow obtained with weld.

Titanous Salts as Stripping Agents. — In consequence of their powerful
reducing action, the titanous salts axe capable of destroying many colours on
the fibre which do not readily yield to the action of bleaching powder. The
colours most readily affected by these are the azo dyes, notably when dyed on
cotton, though certain other colours may also be discharged, or, at least,
suitably modified by their use.

COPPER {Cuprum), Cu = 63-6.

Copper is bivalent. It is a red-coloured metal of 8-94: specific gravity,
which melts at a bright red heat and is slightly volatilised by white heat ;
it is very malleable and ductile and the best conductor of heat and electricity.
Copper does not oxidise either in dry or in moist air at the ordinary tempera-
ture ; but when strongly heated it is first covered with a thin film of oxide,
reflecting the colours of the spectrum, and is slowly converted into scales of
oxide of copper. Under the influence of the carbonic acid in the atmosphere
it is converted into basic carbonate of copper. Steam is not decomposed by
red-hot copper. Hydrochloric acid dissolves this metal only when in a very
fine state of division, with evolution of hydrogen. Nitric acid, both con-
centrated and diluted, dissolves copper, even in the cold, but more rapidly
when heated, forming nitrate of copper with evolution of nitrous gases.
Sulphuric acid does not act on copper at the ordinary temperature ; when
heated with the strong acid the metal is dissolved and copper sulphate formed,
while sulphur dioxide escapes.

.Many valuable alloys contain copper as their chief constituent — e.g., brass
and all kinds of bronze.

Copper combines in four proportions with oxygen, of which only the two
following possess more than a scientific interest :—

Cuprous Oxide, Cu.,0 (Bed Oxide).
Cupric Oxide, CuO (Black Oxide).

* Joxirn. Soc. Dyers and Col., 1903, p. 106.



COPPER. 283

Cuprous Oxide, CugO, is formed by heating a solution of copper tartrate
in caustic soda with grape sugar. It is a bright red powder that does not
oxidise in the dry state. It is used in glass painting, and imparts to the
glass a fine ruby red colour. A yellow hydroxide of the composition
4CuoO 4- H.^0 = Cug03(OH)2 is obtained by precipitating cuprous chloride
with caustic soda. This compound oxidises readily in the air. Cuprous
oxide and hydroxide are readily soluble in ammonia ; the colourless solution
ra[)idly becomes blue by oxidation when exposed to the air.

Cupric Oxide, CuO {Black Oxide or Monoxide of Copper). — Cupric oxide is
a black amorphous, slightly hygroscopic powder which is insoluble in water,
but dissolves readily in acids. Copper oxide dissolves in ammonia with a
beautiful intensely blue colour ; the ammonio-cupric liquid has the power
of dissolving cellulose (cotton and other vegetable fibres) ; the presence
of considerable quantities of mineral salts prevents the cellulose from
dissolving in the liquid or precipitates it from the solution. Cupric oxide
gives off its oxygen readily in presence of reducing substances, and acts as
an oxidising agent.

Cupric Hydroxide, Cu(0H).2, is obtained as a light blue precipitate on
additi(jn of caustic alkalies to the solution of a cupric salt. It can be dried
over lime without changing; the freshly precipitated moist hydroxide when
dried at 100° becomes black and loses water, a hydroxide (Cu30.,(OH.)2) being
formed. Cupric hydroxide does not dissolve in alkalies and has no acid
character ; it is a moderately strong binacid base.

Cuprous Salts are little known in the pure state, since most acids
decompose them, separating the metal in the free state, and forming cupric
salts. The salts are colourless, and rapidly absorb oxygen from the air,
forming cupric salts.

Cuprous Chloride, CuX'U, is obtained as a solid white substance by
dissolving a mixture of metallic copper and cupric oxide in hydrochloric
acid.

Cuprous Sulphocyanide or Thiocyanate, Cuo(CNS)2, is used by calico-printers
under the name White Paste. It is obtained by precipitating a solution of
blue vitriol, containing ferrous sulphate or sulphurous acid with potassium
sulphocyanide. The white precipitate is insoluble in water. It is used in
the production of Aniline black.

Cupric Salts. — Most of the normal salts are soluble in water. The soluble
salts redden blue litmus, and have a disagreeable taste ; they are decomposed
at a low red heat, except blue vitriol, which withstands a slightly higher
temperature. The salts are white in the anhydrous state ; when they contain
Avater they have a blue or green colour, which is perceptible in very diluted
solutions. All compounds of copper are poisonous.

Caustic potash and soda precipitate from the solutions cupric hydroxide ;
alkaline carbonates precipitate insoluble basic cupric carbonate ; ammonia in
excess produces an intensely blue solution of a basic double salt ; the carbonate
of ammonia acts in the same manner. Sulphuretted hydrogen and ammonium
sidjthide precipitate from solutions of copper salts black copper sulphide
(CuS), which is insoluble in diluted acids and in alkalies and little soluble
in alkaline sulphides. Metallic iron in contact with solutions of copper salts
is immediately coated with a film of copper, and is rapidly dissolved ; the
copper in the salt is replaced by iron — Fe + CuSOj = FeSO.j + Cu.

Basic Salts of Copper are insoluble in water.

Cupric Sulphate, CUSO4 + 5H,0 — Blue Vitriol, Blue Stone, Copper
Sidphate. — Cupric sulphate is manufactured by roasting ores which contain
copper and by dissolving them in sulphuric acid. From this solution crystals
having different degrees of purity are obtained ; the chief impurity is iron.



284



A MANUAL OF DYEING.



Cupiic sulphate crystallises in transparent, blue triclinic ci'ystals, which
contain only 5 molecules of water of crystallisation, whereas the other
metallic sulphates, known as " vitriols " — e.g., ferrous sulphate — contain 7
molecules. 100 parts of water dissolve at —



10' c.


20° c.


30= C.


50° C.


70' C.


90° C.


1C0° 0.


Parts.
37


Parts.
42


Parts.
49


Parts.
6'o


Parts.
95


Parts.
156


Parts.
203



Blue vitriol is insoluble in absolute alcohol, and but slightly soluble in
diluted alcohol. It loses 4 molecules of water at 100° and the last at 2^0° to
240°, forming a white mass. The anhydrous salt attracts water readily, and
turns blue ; use is made of this reaction to demonstrate the presence of
water in organic liquids — e.g., alcohol. Blue vitriol is extensively used in the
arts ; for example, in the manufacture of copper colours, and in dyeing.

Cupric Chloride, CuClg, is formed when copper is acted upon by chlorine
gas, or when cupric oxide or carbonate is dissolved in hydrochloric acid. It
forms a brownish-yellow powder in the anhydrous state, and crystallises in
bluish-green rhombic crystals (CuClj + 2H2O). Cupric chloride is very
soluble in water and in alcohol, and is deliquescent. The alcoholic solution
burns with a beautiful green flame, and gives the Bunsen flame a green rim, by
which reaction minute quantities of copper may be detected, e.g., on the
textile fibres.

Cupric Nitrate, Cu(Isr03)o, is obtained by dissolving copper or cupric oxide in
nitric acid. Calico-printers prepare it also by the double decomposition of blue
vitriol and lead nitrate. The salt forms fine blue prisms, Cu(N03)2 + 3H.,0.
On being heated to 65° nitric acid is given off; hence the anhydrous salt is
not known. Cupric nitrate is very soluble in water and is deliquescent.
Since it is decomposed at comparatively low temperatures it is a strong
oxidising agent.

Cupric Carbonate, CuCOg, is not known in the pure state. By adding a
solution of an alkaline carbonate to a cupric salt, a basic salt, CuCOg -f-
Cu(OH).„ is obtained which is insoluble in water. Various minerals consist
of basic cupric carbonates.

Cupric Acetate, Cu(C2H302)2 + H.^O, is obtained by dissolving cupric
oxide, verdigris, or a carbonate of copper in acetic acid, or by the double
decomposition of copper vitriol and lead acetate. It forms dark bluish-green
monoclinic crystals, which efiloresce in the air and dissolve in 13 -4 parts of
cold and in 5 parts of hot water, also in alcohol. The solution gives off
acetic acid on boiling. An acid salt, Cu(C.,H302)„C2H402 -t- H2O, has been
prepared.

Basic cupric acetate or blue verdigris is 3Cu(C.,H30^)(OH) -t- 511^0. It is
prepared by placing sheets of copper into acetic acid or into the fermenting
husks of grapes. The salt forms blue crystals, and occurs in commerce in
greenish-blue lumps, which also contain basic cupric carbonate and sometimes
.gypsum. On treatment with water the salt is decomposed into the normal
and a more basic salt : green verdigris, 2Cu(C2H302)2,CuO. Still more basic
cupric acetates are also known.

Copper Sulphide, CuS, is obtained as a black precipitate by passing a
current of sulphuretted hydrogen through a solution of a copper salt. Lauber
gives the following instructions for preparing copper sulphide : mix 1 250 grms.
(1^ lbs.) of flowers of sulphur with 5 litres (|- gall.) caustic soda (70° Tw.), and
heat on the water-bath, with frequent stirrings, until all is dissolved; pour



LEAD. 285

the solution, with constant stirring, into a solution of 6 kgs. (6 lbs.) of blue
vitriol in 150 litres flS galls.) of tepid water, allow the precipitate to settle,
and wash it several times with tepid water, by decanting ; to the filtered
paste of copper sulphide, which should amount to 12 kgs. (12 lbs.), add