Johannes Rudolf Wagner.

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being used gutta-percha is cleansed from dirt by a mechanical process of kneading
in warm water, being then usually rolled into thick plates or sheets. The purified
material exhibits a chocolate-brown colour, is not transparent unless first reduced to
sheets as thin as paper, when the gutta-percha is in transparency equal to horn. At
the ordinary temperature of the air gutta-percha is very tough, stiff, not very elastic
nor ductile. Every square inch of a strap of gutta-percha, if of goqd quality and as
homogeneous as possible, caja sustain a strain of 1872 kilos, without breaking. Its
sp. gr. = 0*979. At 50** it becomes soft, and at 70** to 80** it is so soft as to be very
readily moulded, while two pieces pressed together at this temperature become
perfectly joined. By the aid of heat gutta-percha can be rolled into sheets, drawn
into wire, and kneaded into a homogeneous mass with caoutchouc.

BatToitaof ontta-pardift. Outta-percha is insoluble in water, alcohol, dilute acids, and
alkalies ; it is soluble in warm oU of turpentine, sulphide of carbon, chloroform, coal-
tar oil, caoutchouc oil, and in the somewhat similar oil obtained by the dry distilla-
tion of gutta-percha. Ether and some of the essential oils render gutta-percha pasty.
As already stated this substance becomes soft in hot water, absorbing a small quantity,
which is only very slowly driven off. Dry gutta-percha is a very good insulating
material for electricity.

uaw of ontte-Fwdm. The natural properties of this substance indicate its use as a sub^
stitute for leather, papier mach6, cardboard, wood, millboard, paper, metal, Ac, in all
eases not exposed to the action of heat, and where a substance is desired resisting water,
aleohol, dilute acids, and alkalies. The raw material, previously to being moulded into
ahape, is purified and kneaded by means of powerful machinery and with the assistance -
of hot water (some soda or bleaohing-powder solution being added), the aim being
the removal of such impurities as are only mechanically mixed with the gutta-percha as
well as the removal of some of the colouring matter, while a more homogeneous mass is
produced. The purified substance is next submitted to the action of kneading moohinezy
similar to that in use for working up caoutchouc, while it is rolled out into plates of some
3 centimetres in thickness. Gutta-percha is moulded into tubes by the aid of machinery
similar to that employed for making lead and block-tin tubing. Many objects are made
from gutta-percha by pressing it while soft into wooden or metal moulds. By the use of



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48« CHEMICAL TECHNOLOGY.

a Bolntion of gnita-peroha in benzol, it may be glued to leather and similar snbstaneea.
It is almost impossible to enumerate the various uses of gutta-percha. It is employed
for straps for machinery instead of leather, tubes for oouT^ying water, pumps, pails, sur-
gical instruments, ornamental objects of Tarious kinds, for coTering telegraph wires, ^te.
Unlike pure caoutchouc gutta-percha becomes graduaUy deteriorated by exposure to the
atmosphere, so that it can be even readily ground to powder.
Hixtan of Gntu-Paeha Frequently a mixture of i part of gutta-i>ereha and a parts
Mid OMutehoufi. of caoutchouc is employed. Articles made of ibis eompound
possess the properties of both substances, and may be vulcanised equally aa well as
gutta-percha alone. A mixture of equal parts of caoutchouc, gutta-pei^ha, and sulphur,
heated for several hours to 120°, obtains properties similar to those of bone and horn.
Sometimes gypsum, resin, and lead compounds are added to this mixture, which is them
used for making knife hafts, buttons, &o,

vaxniihca. By vamish we understand a liquid of an oily or resinoas nature
employed for coating various objects, the thin film becoming dry and hard, thus
protecting the object on which it is laid firom the action of air and water, .and
at the same time imparting a glossy and shining surfieu^. We distingiiiah aQ and

oiivaniihw. spirit varnishes. Oil varnishes are usually prepared from linseed oil,
but sometimes, especially for artist's purposes, poppy seed and walnut oil (so-called
drying oils) are used. Linseed oil (raw) becomes slowly converted by the aetioa of
the air into a tough, elastic, semi-transparent mass ; but this property is possessed in
a £eu: higher degree by the so-called boiled oil, that is to say — an oU which has been
brought by the action of heat and of oxidising materials into a state of greater
activity, in fact — ^into a state of incipient slow oxidation, the result of which is the
formation of the substance termed by Dr. G. J. Mulder * linoxine, which in many of
its properties corresponds to caoutchouc. The drying of oil varnishes is not there-
fore due to evaporation (leaving, as is the case with alcohol varnishes, a coherent film
of resin), but to the oxidising action of the oxygen of the air, whereby a coherent
film of linoxine is formed. Linseed oil (raw) is converted into what is termed
vamish by heating the oil with certain substances which more or less readily give off
oxygen, while these substances also act upon the elaine, palmitine, and myristine of
the linseed oil. The greater part of the linseed and other drying oils is linoleine,
3(03aH27O3),C6HjO3, which by slow oxidation becomes linoxine = C32HJ17OXX, by
the action of alkalies converted into linoxic acid, HO,C32H2509. The substances
with which raw linseed oil is boiled are litharge, oxide of zinc, and peroxide of man-
ganese. It is certainly preferable to carry this operation into effect upon the water
bath, or at least with vessels provided with steam jackets. The oxides are employed
in coarse powders, which are suspended in a linen bag in the oil. In practice i part
of oxide of zinc or litharge is taken to 16 parts of raw oil ; and of the manganese
I part to 10 of oil ; the oxides become partially dissolved in the oil, while they aid
in converting the palmitine, &c. (not linoleine), into plaster (lead or zinc soap).
Boiled linseed oil usually contains from 2*5 to 3 per cent of lithax^e dissolved.
Neither the addition of sulphate of zinc nor such absurdly added substances as
onions, bread crust, or beet-root have any result whatever. Linseed oil intended to
be mixed with zinc-white should not be boiled with litharge, but with peroxide
of manganese. The lower the temperature at which linseed oil is boiled the brighter
its colour. Mulder found that when raw linseed oil, especially if old, was kept for
12 to 18 hours at a temperature of 100**, it acquired the property of boiled oiL
Sometimes after boiling linseed oil is bleached b; exposing it in shallow trays

* This author published some years ago in the Dutch language a highly interesting and
valuable work— practically as well as scientifically— on the drying-oils.



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VARNISHES. 489

to oentuns. deep, best made of sheet lead, covered with sheets of glads, to the action
of strong summer sunlight. Liebig's recipe for making a bright varnish is the
following : — To 10 kilos, of raw linseed oil are added 300 grms. of finely pulverised
litharge, after which there is added a solution of 600 grms. of acetate of lead ; the
mixture is vigorously stirred, and after the siftsidence of the materials the clear
-varnish is ready for use. Borate of manganese is, according to Barruel and Jean,
an excellent so-called siccative (dryer) when added to raw linseed oil, i part to 1000
of oiL Mulder's experiments confirm thia^tatement in every respect.

oousiaa. TMs is used in gilding for fixing gold leaf on wood, paper, <fec., and consists
of a solution of linseed oU and lead plaster in oil of turpentine, prepared by first
aaponif^g linseed oil with caustio soda or potassa, and precipitating the aqueous
Bolttiion of the soap with a solution of acetate of lead, the lead soap thus formed being
next dissolved in oil of turpentine.

viiatiiigink. This is, when genuine and prepared from good linseed or walnut oil,
anliydride of linoleic acid, C3sHt703, mixed with very finely divided lamp-black, and
obtained by heating raw linseed oil for several hours, at a high temperature
(315*" to 360°), whereby the fatty constituents — glycerine, palmitine, &c. — are
volatilised. Usually the oil is heated in vessels directly exposed to the action
of fire, and as the colour of the ink is black, a deep colour of the residue of the
heating of the oil is not of much consequence. In order to render printing ink more
rapidly drying, some borate of manganese m^y be heated with it at 315"* for some
hours. The quantity of fine lamp-black (best re-ignited in close vessels, or exhausted
with boiling alcohol) usually added to printing ink, amounts to about 16 per cent
Soap is added in order to prevent smearing and assist in obtaining sharpness
t>f impression. Coloured printing inks are obtained by adding to boiled oil red or
blue or other pigments ; for red vermillion is used. The ink used in lithography
and copper-plate printing is made thicker, a better black being added.

oavamidM. The so-called &t or oil varnishes are solutions of resins in boiled lin*
seed oil mixed with oil of turpentine, benzol, or benzoline. Amber, copal, anime,
gum dammar, and asphalts, are among the more ordinary resins employed for this pur-
pose, the varnishes being made by melting, with the aid of gentle heat, the amber,
copal, Ac., to which, while liquid, boiling linseed oil is added. The cauldron in
which this operation takes place should only be two-thirds filled ; and the mixture of
oil and resin kept boiling for ten minutes. The cauldron having been removed from
4he fire its contents are allowed to cool down to 140% when the oil of turpentine is
added. The quantities by weight are 10 parts copal or amber, 20 to 30 boiled
linseed oil, 25 to 30 oil of turpentine. Black asphalts varnish is obtained in a
flimilar manner by treating 3 parts of asphalts, 4 of boiled linseed oil, and 15 to 18
parts of oil of turpentine. Dark coloured amber varnish is not prepared from
amber but from the residue (ofnber oolophonium) of the distillation of the empy-
lenmatic oil of amber and succinic acid left in the still from the preparation of
succinic acid. These varnishes are the most durable, but they dry slowly and
are more or less coloured.

spiiuvaniidL The so-called spirit varnishes are solutions of certain resins,
viz. sandarac, mastic, gumlac (shellac), anime in alcohol, aceton, wood spirit,
benzoline, or sulphide of carbon. Good spirit varnish ought to dry rapidly, give a
gfksy surface, adhere strongly, and be neither brittle nor viscous. As shellac is
frequently employed, the name of lac varnish is sometimes given to these vaimshes.

The spirit, usually methylated spirit, ought to be strong, about 92 per cent. The



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490 CHEMICAL TECHNOLOGY.

Boltttion of the resins is promoted by the addition of one-third of their wei^t
of coarsely powdered glass for the purpose of preventing the resinous matter caking
together, and being thus to some extent withdrawn from the solvent action of
the alcohol. In order to render the coating remaining from the evaporation of
the spirit less brittle, Venice turpentine is usually added. Sandarac vamish
is obtained by dissolving lo parts of sandarac and i of Venice turpentine in 30 of
spirit. Shellac varnish, more durable than the former, is obtained by dissolving
z part of shellac in 3 to 5 of spirits. French polish is a solution of shellae in
a large quantity of spirits, and when this polish is to be applied to white wood, the
varnish is bleached by filtration over animal charcoal. Copal varnish, far superior
to the foregoing, is made by first melting the resin at as gentle a heat as possible
80 as to prevent the colouration of the substance, which is next pulverised, mixed
with sand, treated with strong alcohol on a water bath; and filtered. A solutLoo
of turpentine or elemi resin is added to render the varnish softer. Colourless eopal
varnish is obtained by pouring over 6 kilos, of previously pulverised and nudten
copal, contained in a vessel which may be closed, 6 kilos, of alcohol at 98 per cent,
4 kilos, of oil of turpentine, and i kilo, of ether ; the vessel containing this mixture
having been closed is gently heated. The solution is clarified by decantation.

odourad spirit vunidMi. These are used chiefly for the purpose of coating instruments,
and other objects of brass and coloured metallic alloys, so as to prevent the action
of the atmosphere. Such varnishes are used for imparting a gold-colouT to
base metals; for this purpose alcoholic tinctures of gummi-gutta and dragon's blood,
or fuchsiu, picric acid, Martins yellow, and corallin, are separately prepared and
added, in quantities found by trial, to a varnish consisting of 2 parts of seed lac, 4 of
jnmdarac, 4 of elemi, and 40 of alcohol.

TiiipttitiiMoavaaidiw. Those are prepared in the same manner as the preceding.
They dry more slowly, but are less brittle and more durable. Common turpentine
oil varnish is obtained by dissolving ordinary resin in oil of turpentine ; but dus
varmsh is liable to crack. Copal is either dissolved in oil of turpentine, without or
after having been melted ; in the latter case the varnish being coloured. When non-
melted copal is used it is broken into small lumps, and is suspended in a stout canvas
bag over the sur&ce of the oil of turpentine contained in a glass flask and placed on
a sand bath, the vapours arising from the oil of turpentine gradually dissolving fbB
copal. Dammar gum resin varnish made with oil of turpentine is prepared by
drying the resin at a gentle heat and dissolving it in three to four times its wei^t of
oil of tupentine. This varnish, though colourless, is not very durable. Green
turpentine oil varnish is prepared by dissolving sandarac or mastic in concentrated
caustic potash solution, diluting with water, and precipitating with acetate of copper,
the dried precipitate being dissolved in oil of turpentine.

PdiiahinfftheDriedTanidi. In order to increase the gloss of varnished snrfaoes, espedally
on metallic objects and coaches, carriages and woodwork in theatres, concert-rooms,
halls, (&o., the dry surface is first mbbed over with soft felt, on which some very fine pumiee>
powder is laid, and is next polished with very soft woollen tissue on which some oil and
rotten-stone is placed, the oil being rubbed off with starch-powder. Instead of vamisfaes,
solutions of collodion (fulminating cotton in alcohol and ether) and solutions of water-
glass are sometimes used; while Puscher recommends a solution of shellac in amg^onia,
largely used by hatters.

psttankofafi Proeanfor In Order to rcmove the cracks often observed in old pictures. Von

BMioring pictnreg. Pettenkof cr has suggested exposure to the vapour of i^eohol at the

ordinary temperature of the air, the picture being placed in an air-tight box, at the bottom

of which is a tray containing alcohol. This metiiod has been tried, but not only has it



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■'-.V*



CEMENT. ' 4gx

failed in many eases, bnt some piotnres haTo been aotaaUy spoiled. Aoeording io
Dr. G. J. Mnlder's researohes, the only effective preservatiYe of pictures is oomplete
exclusion of air. He saggests that pictures shonld be well Yamished on the painted side
as well as on the back, and next hermetically covered with weU-fitting sheets of polished
glass on the front, and some substance on the back impermeable to air. The real canse
of the ultimate destruction of pictures as well as of paint is the gradual but continuous,
yet slow, oxidation of the linoxine, resulting in. the crumbling to powder of the pulverulent
matters — ^pigments, used as colours. It may not here be out of place to state that one of
the best solvents of linoxine (dried paint) is a mixture of alcohol and chloroform, which
may be advantageously used to remove stains of paint, and also of waggon and carriage
grease from silk and woollen tissues.

Cements, Lutes, and Puttt.

ooMta. In a general sense we understand by cement, substances or mixtures
which, when placed in a pasty state between the surfiaces of bodies in close contact,
cause them to adhere solidly after the drying or solidification of the pasty material.
According to this definition, glue and paste are cements, but solder is not. As a
universally applicable cement cannot be met with, it is clear that as regards any
specific cement it should completely answer the purpose for which it is employed.
The substances used for cement are very various, and are of course adapted to the
particular objects they are intended to unite. There are numberless receipts for the
preparation of cements, which may be best classified by stating the name of the most
essential constituent. Thus we have: — i. Lime cements. 2. Oil cements. 3. Resin
and sulphur cement 4. Lron cements. 5. Starch, or paste. 6. Cements of less
consequence, as, for instance, water-glass cement, chloride of zinc cement, &c.

umommdu. Slaked-lime forms with casein, white of eggs, gum-arabic, and glue,
mixtures which after some time become very solid, and are used to unite wood,
stone, metal, glass, porcelain, &c.

Casein cement may be made in various ways, but is most usually prepared by
mixing freshly-precipitated casein, obtained by acidifying milk, previously freed from
whey and separately reduced to powder, with freshly slaked lime. As this masd
hardens very rapidly, it should be used immediately, and not prepared iu larger
quantity than may be required. Casein dissolved in bicarbonate of potash or soda
solution, and gently evaporated to a thick consistency, also yields a good cement
A solution of casein in a concentrated aqueous solution of borax made with cold
water yields a clear thick solution, which, as regards adhesive property, far surpasses
a solution of gum-arabic. A solution of casein in silicate of soda or potash is an
excellent cement for glass and porcelain. When stone, metal, wood, &c., are to be
united, or when the cement is to be used for filling up small cavities, there is usually
added to the mixture of casein and lime a powder made of i kilo, of fresh casein,
I kilo, of quick-lime, and 3 kilos, of hydraulic mortar or lime. According to Hannon
parUy decayed and liquefied gluten yields with lime a cement similar to that
obtained from casein.

oaocBB«nti. The main and essential constituent of these cements is a drying oil in
the shape of an oil varnish (boiled linseed oil). Most of these cements resLst the
action of water.

Boiled linseed oil and fat copal varnish may be used as cements to unite glass and
porcelain, but are seldom so employed on account of requiring some weeks to become
dry. Mixed with white-lead, litharge, or minium (red lead), the cement dries mora
quickly, but does not become quite hard until after some weeks. When a larger



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49a CHEMICAL TECHNOLOGY.

quantity of this cement, or rather putty, is required, it is frequently made of boiled
linseed oil with a mixture of lo per cent of litharge and 90 per cent of either washed
chalk or slaked lime. Zinc-white is sometimes used instead of litharge. This putty
is frequently wanned before use in order to render it softer ; it is used for uniting
stone, brick, &c. A mixture of 2 parts of litharge, i of slaked lime, and i of dry sand,
made into a uniform paste with hot and boiled linseed oil, has been used by Stephenson
as a putty to be placed into the sockets of steam-pipes. By precipitating a
solution of soda-soap with alum solution an alumina soap insoluble in water is
obtained, which, having been dissolved in warm linseed oil varnish, yields, according
to Yarrentrap, an excellent cement for uniting stone. Glaziers' putty is a mixture of
chalk and boiled linseed oil, well beaten up together. When this putty is made with
raw linseed oil it hardens very slowly ; prepared with boiled linseed oil it nmy be
kept soft for a considerable time by either being placed under water, or kept in
bladders like lard, or tied up in canvas bags previously soaked with piL According
to Hirzel, a mixture of litharge and glycerine forms an excellent cement and readily
hardening lute, which, according to Pollack, may even be used to unite iron and iron,
as well as iron and stone.
Basin oanenta. Gemcuts made with resin as the main constituent are often used,
because, on becoming cold, they harden at once and possess the property of being
waterproof; on the other hand, these resin cements will not endure a high tempera-
ture witliout becoming soft, and by exposure to air and sunlight they become so
brittle as to be easily pulverised.

As a cement for glass and porcelain, sandarac and mastic are sometimes used,
because these resins are readily fusible and are colourless. They are applied to the
surfaces to be united in the form of a powder put on with a small hair-brush, after
which the object is heated so as to melt the resins, the pieces to be joined being
pressed together. As tin back as the year 1828, Lampadins suggested as an excel-
lent cement a solution of i part of amber in 1*5 parts of sulphide of carbon.
When this solution is painted over the surfo,ces to be united and immediately
pressed together, the joint is at once effected owing to the rapid evaporation of the
sulphide of carbon. A solution of mastic in sulphide of carbon may be similarly
used. Shellac alone does not form a good cement, being too brittle when cold, and
contracting too much after having been melted : the addition of some Venice turpen-
tine and earthy powders (see Sealing-wax) compensates these defects. While wood
cannot be joined together with shellac, it is firmly and readily glued by coating the
pieces to be joined with thick sheUac-vamish, and then placing between the two
pieces a slip of muslin. Kesins are frequently used for lining water-cisterns, and for
rendering terraces, Ac., waterproof. Pitch, colophonium, asphalte, mixed with lime,
sulphur, or turpentine, are used for this purpose, the object of the various additious
being to obtain a greater or less degree of hardness. Jeffery's marine glue is
prepared by dissolving caoutchouc in twelve times its weight of coal-tar naphtha and
adding twice the weight of either asphalte or shellac. The mixture is gentiy heated
to render it uniform. There is a solid and a fluid marine glue, in the trade ; the
former is used for glueing wood and for caulking, the latter, obtained simply by &e
use of a larger quantity of solvent, is used as a varnish ; both kinds are insoluble in
water, are not acted upon by change of temperature, and do not become brittle. By
the name of zeiodelite is understood a mixture consisting of 19 parts of sulphur and
42 of powdered glass or earthenware; this mixture having been heated to the



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PASTS. 493

melting-pomt of sulphtur, maybe used, instead of hydraulic cement, for uniting stones
and bricks. R. Bottger prepares this cement by mixing with molten sulphur an
equal weight of infusoria earth to which some graphite is added. Under the name
of diatite Merrick prepares a mixture of shellac and finely divided silica.

izoaOMMiit. Among the very many recipes given for the preparation of this cement,
used for luting the sockets and spigots or flanges of cast-iron pipes, and for caulking
the seams of the plates of steam-boilers, we quote the following as one of the best : —
A mixture of 2 parts of sal-ammoniac, i of sulphur, and 60 of finely-pulverised cast-
iron borings or filings. When required for use, this mixture is made into a paste
with water, to which some vinegar or dilute sulphuric acid is added. The parts to
be joined by this cement should be free from &t, oil, or rust. The cement is forced
in with the caulking-chisel and soon becomes very hard. A lute for small leaks in
iron and fire-clay gas-retorts can be made with 4 parts of iron-filings, 2 of clay, and
I of pulveiised porcelain saggers. This mixture is made into a paste with a solution
of common salt.

PMto. The material used by bookbinders, and, in fad, wherever »paper is to be
glued to paper, is obtained by boiling flour with water or by treating starch with hot
water.

Starch paste is best made by rubbing the dry starch up with cold water, so as to
form a uniform magma, to which, while being constantly stirred, boiling water is
veiy rapidly added; this paste should not be boiled if required for cementing paper
ti^ether. Rye-meal boiled with water yields an excellent paste, which may be
improved by the addition of some glue solution and preserved by alum. Partiy



Online LibraryJohannes Rudolf WagnerA handbook of chemical technology → online text (page 71 of 109)