Scientific American Supplement, No. 401, September 8, 1883

V >> Various >> Scientific American Supplement, No. 401, September 8, 1883

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For the manufacture of my sensitized film paper:

First. A gelatinized sheet of paper is properly damped with cold water,
and when evenly saturated it is placed on a glass, to which it is
attached by means of bands of paper pasted partially on the glass, and
partially on the edges of the said sheet; in this state it is allowed to
dry, whereby it is stretched quite flat.

Secondly. I coat the dry sheet with a solution of ordinary collodion,
containing from one to two per cent. cubic measure of azotic cotton (11/2
per cent. gives very good results) and from 11/2 to 21/2 per cent. of castor
oil (2 per cent. gives very good results); this coating is allowed to
dry; and,

Thirdly. The glass, with the prepared paper upward, is leveled, and then
it is coated, in a room from which all rays but red rays of light are
excluded, with a tepid emulsion of bromide of silver to the extent of
about one millimeter thick, and after leaving it in this position until
the gelatine has set (say) about five minutes, with the film paper still
attached, it is placed upright in a drying-room, where it should remain
about twelve hours exposed to a temperature of from 62 to 66 degrees
Fahrenheit; and,

Fourthly. The film paper is detached from the glass ready for exposure,
development, and fixing in the usual manner. For the purpose of
developing, oxalate of iron or pyrogallic acid answers equally well; for
the purpose of fixing, I have found that a mixture by weight, water,
1,000, hyposulphite of soda 150, and powdered alum 60, produces
excellent results, after being allowed to dry.

Fifthly. The film is peeled off the paper by hand, and can be
immediately used for producing negatives _recto_ or _verso_ as above
mentioned.

I claim as my invention:

First. The preparation or formation of gelatino-bromide film paper
for photographic negatives, in the manner and for the purposes above
described; and,

Secondly. The use for this purpose of castor oil, or any other analogous
oil, more especially with the view of peeling off the film from the
paper backing as above described.

* * * * *

SOME OF THE USES OF COMMON ALUM.

A substance very much used by photographers of late years--in fact, so
much used that no well-appointed laboratory could be considered complete
without it--is the substance known is common alum, or potash alum, being
a double sulphate of alumina and potash; but it is interesting to note
that much of the commercial alum met with at the present time is ammonia
alum, or the double sulphate of alum and ammonia. It is quite a matter
of indifference to the photographer whether he uses potash alum or
ammonia alum.

Besides its great value to the autotype, Woodburytype, and mechanical
printers as an agent for hardening the gelatine films, it has been
recommended for all sorts of ailments photographic. The silver printer
adds a small portion to his sensitizing bath to keep it in working
order, and to prevent blistering of the albumen; then, again, silver
prints are soaked in a dilute solution of alum, having for its object
the thorough elimination of the last traces of the fixing salt. A very
good proportion to use for this latter purpose is four fluid ounces of a
saturated solution, diluted with one gallon of water, the prints being
well agitated during an immersion of ten minutes.

Of all the uses to which alum is put, perhaps not in any single instance
can so much satisfaction be derived as when it is used to
arrest frilling of gelatine plates. This it has the power to do
instantaneously, and many of the most careful workers, both amateur and
professional, or at least those who do net care to run any unnecessary
risks with negatives which have cost them a good deal of anxiety and
trouble to secure, but prefer to make assurance doubly sure--such
individuals may be numbered by the hundred--make it a point in every-day
practice to immerse all their plates in a solution of alum, either
before fixing, or immediately afterward. In fact, some operators have
two alum baths in use, one a normal bath, as above mentioned, for
immersing the plates in when of the ordinary printing intensity; and the
other a saturated solution strongly acidified by means of a vegetable
acid (such as citric) or a mineral acid (such as sulphuric), for use
when there is too much printing density, since it has been found
in practice that an acid solution of alum in contact with sodium
thio-sulphate on the gelatine image (after fixing, but before washing)
not only removes the color or stain caused by the alkaline or
pyrogallol, but perceptibly reduces the strength of the image. Moreover,
the color does not again reappear after washing, as it does sometimes
when the fixing salt has been partially washed away. In cases where
there is great tendency to frill--such, for instance, as when a soft
sample of gelatine has been employed, or old decomposed emulsion worked
in with the fresh emulsion--it will in such cases be safer to put the
plates in the normal-bath for a few minutes previous to immersing them
in the acid bath.

Potash alum is obtained tolerably pure in commerce in colorless
transparent crystalline masses, having an acid, sweetish, astringent
taste. It is soluble in 18 parts of water at 60 deg. F., and in its own
weight of water at 212 deg. F.; but the excess crystallizes out upon
cooling. The solution reddens litmus paper, and, when impure, usually
contains traces of oxide of iron. Upon the addition of either caustic
soda or potash, a white gelatinous precipitate is formed (hydrate of
alumina), which is soluble in excess of the reagent employed. The
precipitate thus obtained has much of the character of the opalescent
film sometimes observed on gelatine plates, when dry, which have been
soaked in alum, and not well washed afterward.

Alkaline carbonates--such as washing soda, for instance--precipitate
hydrate of alumina, which does not dissolve in an excess of the
reagents, and carbon dioxide is evolved.

Ammonia hydrate produces a precipitate in a much finer state of divison,
which does not dissolve in excess when examined in a test-tube, it
somewhat resembles thin starch paste.

The presence of traces of iron may be known by adding a few drops of
hydrochloric acid to a small quantity of a saturated solution of alum
in a test-tube, to which add strong liquid ammonia; should any iron be
present, the mixture will have a reddish-brown tinge when examined over
a sheet of white paper. Other alums exist, such as the double sulphate
of alumina and sodium, and sodium or aluminum and ammonium; but hitherto
their uses have been confined to the experimental portion of the
community rather than the practical.--_Photo. News_.

* * * * *

CLOTH STRETCHING MACHINE.

As is well known, in the process of bleaching and dyeing, cotton cloths
become considerably contracted in the width, in consequence of carrying
on the operations when the cloth is in the form of a rope. The effect is
that, together with the tension, although slight, and the drying, the
weft partly shrinks and partly curls up, the latter, however, being
scarcely observable to the naked eye. It may almost be said that as
regards the width the shrinkage is due to a number of minute crumples
because the cloth is easily streatched again by the fingers almost to
its gray width. The main use of a stretching machine, therefore, is not
so much to make the cloth more than it is as to bring it again to its
normal or woven width after operations that tend to shrinkage have been
performed upon it. The stretching operation, therefore, is especially
useful to calico printers, as it enables them to obtain when desired a
white margin of even width, the irregularities due to bleaching being
corrected before printing.

[Illustration: IMPROVED CLOTH STRETCHING MACHINE.]

The machine now illustrated is one we have recently seen in operation in
a Salford finishing works. It is an improved form of another stretching
machine which had been turned out in considerable numbers by Mr.
Archibald Edmeston, engineer, of Salford, who makes a specialty of
calico printers' and finishers' machinery. The improvements consist
mainly of a simplification of the working parts and thoroughly
substantial construction of the machine. The principle adopted is a
well-known one. The selvages of the cloth, or more strictly the two
edges of the cloth, of a width of about two inches, are caused to pass
over and at the same time are held by the rims of two diverging pulleys.
The rims are further apart where the cloth leaves them than where they
seize it, hence the stretching is gradually, certainly, and uniformly
performed. The cloth is gripped by the pressure of an endless belt
acting against the lower half of each pulley, the edges being held
between them. In the engraving these stretching pulleys are indicated by
the letters AA; the endless leather band passes over the pulleys, CC, of
which there are a set of four provided for each stretching pulley. The
lower pair of pulleys in each case may be tightened up by a screw
for the purpose of imparting the requisite tension to the bands. The
stretching pulleys are mounted upon and driven by the same shaft, an
ingenious but simple swiveling joint in their bosses enabling them to
be set at any angle to the shaft and yet to revolve and be driven by it
without throwing any undue strain upon the working parts. The piece,
wound upon the ordinary batch shell, is placed upon the running-off
center, D; it is led off over the rails, EE, and then downward to the
nip of the bands and pulleys, AA. As explained, the selvages are here
gripped between the bands and stretching pulleys, the rims of which are
wider apart at the back than the front, and thus, in being conveyed
underneath, the piece is suitably stretched. Leaving the grip at the
back it passes over leading-off rollers, FF, and the scrimp or opening
rail, G, and thence downward to the winding-on center, which cannot be
seen. The winding-on center is driven by friction. As the batch fills
it and tends to wind faster than the machine delivers the cloth, the
driving slips. In addition to a capability of being set at an angle to
the shaft, the stretching pulleys, AA, may be slided upon, so as to
separate or bring them closer together, to allow for the treatment of
different widths of cloths. This adjustment is provided for by mounting
the stretching pulleys, AA, and the band pulleys, CC, etc., on frames,
BB, the ends of which rest, as shown, upon rails, at the back and front
of the machine. The adjustment either for width of piece or for the
angularity (extent of stretching) is easily made by the hand-wheel, L.
By the bevel wheels shown, two cross screws having nuts connected to the
ends of frames, BB, are actuated in such a way that as desired the space
between the back and front of the pulleys may be closed in or opened
out, or the two wheels, maintaining the same angularity, may be
separated or closed in, either adjustment being expeditiously made. The
wheels, HHH, are called center stretching wheels, the use of which is
sometimes advantageous. They act in conjunction with a set of stretching
pulleys, of which one, K, may be seen in illustration. By a proper
adjustment at the latter the piece is bent into a wavy form, where it
passes between the whole of them, the effect of the corrugation being
to loosen the center threads and to allow the piece to be more equally
stretched with those near the selvages and more easily. This part of the
machine may be used or not as required. The production, we observe, was
about 120 yards per minute. The machine is solidly built and well fitted
together, as was obvious to us from an inspection of some in course
of construction at the maker's works. It is also claimed to be of
considerable advantage to bleachers and finishers of white goods,
on account of the uniformity of the stretching causing but small
disturbance to the stiffening.--_Textile Manufacturer_.

* * * * *

WOOLEN FABRICS PURIFIED BY HYDROCHLORIC ACID GAS.

All known methods for chemically purifying woolen stuffs from vegetable
fibers depend on the action of acids or substances of acid reaction.
The excessive temperature, hitherto unavoidable in the operation, acts
injuriously on the woolen fibers, especially during the formation of
hydrochloric acid, with which process especially the development of an
injuriously high temperature has been hitherto unavoidable. The best
method of absorbing the heat developed is in the evaporation of the
moisture naturally present in the wool. The patentees find agitation of
the fabric and the use of an exhauster during the process of material
assistance. The operation maybe successfully performed in two
ways--either by acting on the fabric at the ordinary pressure with
constant agitation, or by saturation without agitation in a vacuum. For
the first method the patentees employ a wooden cylinder with an aperture
at one end for inserting and removing the cloth, and having apertures
all round to allow free access of air. This cylinder rests on a hollow
axle, closed at one end and perforated with holes, through which the
acid gas is passed. By the rotation of the cylinder the gas is drawn
through the material and the latter exposed to the atmosphere, whereby
it gives up a quantity of aqueous vapor. An average temperature of 30 deg.
Cent. is best suited to the operation, and it can be regulated according
to the supply of gas by opening or shutting a three-way cock between the
gas generator and the revolving cylinder. This process is assisted by
the use of an exhauster of the usual construction. When fully saturated,
the fabric is allowed to remain until the vegetable fibers are
sufficiently friable. The treatment _in vacuo_ is as follows:

The hydrochloric acid gas passes into a vessel of suitable material
provided with a perforated false bottom. From under this false bottom
a pipe connects with a second similar vessel connected itself with a
vacuum pump having a let-off pipe. As soon as the maximum vacuum is
attained, the gas is turned on through a three-way cock at a pressure of
40 mm. mercury. The gas fills the first vessel and saturates the cloth.
The warmth set free (about 500 calories per kilo, gas) is taken up
by the combined water in the wool, as, owing to the low pressure, a
quantity of vapor is formed sufficient to take up the heat. This vapor
streams through the second vessel at a temperature of 35 deg. Cent.,
penetrates the material, and passes out through the pump. After
saturating the contents of the first vessel the gas passes into the
second. AS soon as this is one-quarter or one-third saturated the first
vessel is taken out and replaced by a third, which receives the overplus
from No. 2 in like manner, and so on. This plan of working prevents gas
passing through and damaging the pump. Instead of working under reduced
pressure, the desired low temperature can be maintained by passing
alternately with the gas currents of air which absorb heat in
evaporating the moisture of the material. The cloth, after saturation by
these processes, is left from six to twelve hours in the vessels, after
which it is freely exposed to the air until the vegetable particles
are friable. As soon as this occurs, the fabrics are washed. It is
advantageous to add to the wash water powdered carbonate of baryta,
strontia, magnesia, or preferably lime, and subsequently to rinse in
pure water. Phosphate of lime containing carbonate may also be employed
for neutralizing the acid, and the residue recovered and separated from
the organic residues mixed with it.--"_H. J.," Journal of the Society of
Chemical Industry._

* * * * *

APPLICATION OF ELECTRICITY TO THE BLEACHING OF VEGETABLE TEXTILE
MATERIALS.

It is a recognized fact that chemical bodies in a nascent state are
characterized by peculiarly energetic affinities, and the results of
numerous experiments permit us to affirm that animal and vegetable
fibers are rapidly bleached when they are placed in contact with oxides
and chlorides which, when submitted to electrolysis, permit oxygen and
chlorine to disengage themselves in the nascent state.

The coloring matter that impregnates the majority of vegetable textile
substances, such as cotton, flax, and hemp, to cite only those most
generally known, is in fact completely destroyed only by the combined
action of oxygen and chlorine, which always act in the same manner,
whether the fibers be in a raw or woven state.

In the application of electrolysis to the bleaching of textile
materials, it is only necessary to have the electrodes of any
sufficiently powerful generator of electricity end in a vessel
containing in aqueous solution such decolorizing agents as the
hypochlorites in general, and chlorides, bromides, and iodides that are
capable of disengaging chlorine, and iodine or an iodide in a nascent
state. These gases perform the role of oxidizing or decolorizing agents.

The fibers that are immersed in the solution during the passage of the
electric current must necessarily remain therein for a greater or less
length of time, according to the nature of the material to be bleached,
and must, after this first operation, be washed, rinsed, and dried.

The use of an electric current for decomposing the metallic chlorides
and disengaging their elements is not new, and there have been specially
utilized for this purpose, up to the present time, the alkaline
hypochlorites that are obtained by well known processes.

In the latter case the metal is brought to the state of oxide in
presence of the water that is necessary for the reaction. But the
results obtained in practicing this method are deceiving, as far as
bleaching is concerned, and it is evidently more rational and economical
to endeavor to compound the hypochlorite directly by borrowing all its
elements from the metallic chloride itself, and from the water by means
of which such transformation is to be effected. This is a reversal of
the problem, and, _a propos_ thereof, we would call the attention of
the reader to an apparatus invented by Messrs. Naudin & Schneider for
effecting such synthesis in a simple and practical manner.

If a solution of chloride of sodium or kitchen salt, NaCl, be submitted
to electrolysis in a hermetically closed vessel containing the material
to be bleached, a formation of hypochlorite of soda is produced in the
following way:

2NaCl + 2 H_{2}O = NaCl + NaO, ClO + 4H.

In operating in this manner we shall have the advantage that results
from the nascent body through the electrical double decomposition of the
chloride of sodium and water, which puts the chlorine, the metal, the
hydrogen, and the oxygen simultaneously in presence. The chlorine and
oxygen will combine their action to decolorize the textile material.

While starting from this idea, it will nevertheless be preferable to
adopt Naudin & Schneider's arrangement.

The apparatus consists of a hermetically closed electrolyzer, A,
into the lower part of which enters the electrodes, E and F, of any
electrical machine whatever. The receptacle, A, is provided with a
safety-tube, T, that issues from its upper part and communicates with
a reservoir, B. A second tube, D, forms a communication between the
electrolyzer and the vessel, C. The liquid contained in this latter is
sucked up by a pump, P, and forced to the lower part of the vessel, A,
by means of the tubes, G and H.

The apparatus operates as follows:

The closed vessel, C, in which the material to be bleached is put, is
filled, as is also the electrolyzer, with a solution of chloride of
sodium. This solution is then submitted to the action of an electric
current, when, as a consequence of the chemical decomposition of
the chloride and the water, the elements in a nascent state form
hypochlorite of soda. When the partial or total conversion of the liquid
has been effected (this being ascertained by chlorometric tests), the
pump, P, is set rapidly in operation, and, as a consequence, draws up
the chloride of sodium from the bottom of the vessel, C, to the lower
part of the electrolyzer, A. The hypochlorite that has formed passes
through the tube, D (as a natural consequence of the elevation of the
level of the liquid in A brought about by the entrance of a new supply
of chloride), and distributes itself throughout the vessel, C, where it
acts upon the textile material.

[Illustration: APPARATUS FOR BLEACHING TEXTILE FIBERS BY ELECTRICITY.]

The safety-tube, T, which is attached to the electrolyzer, permits
of the escape of the hydrogen which is produced during the chemical
reaction, and fixes, through an alkaline solution contained in the
reservoir, B, the chloride whose escape might discommode the operator.

As may be conceived, the slow transfer of the saline solution from
the receptacle, C, to the electrolyzer, and its rapid conversion into
decolorizing chloride, as well as its prompt application upon the
materials to be bleached, presents important advantages.

While, in the present state of the industries that make use of bleaching
chlorides, the chloride of sodium is converted into hydrochloric acid,
which, in order to disengage chlorine, must in its turn react upon
binoxide of manganese, we shall be able, with this new method, to
utilize the chloride of sodium, which is derived from ordinary salt
works, and extract from it the constituent elements of the hypochlorite
by a simple displacement of molecules produced under the influence of an
electric current.

Another and very serious advantage of electric bleaching is that of
having constantly at hand a fresh solution of hypochlorite possessing a
uniform decolorizing power, which may be regulated by the always known
intensity of the current.

We must remark that the hypochlorites require a certain length of time
to permit the chlorine to become disengaged, and that, besides, all
chlorides, bromides, and iodides that are isomorphous are capable of
undergoing an analogous chemical transformation and of being employed
for the same purpose. This is especially the case with the chlorides
of potassium or barium, the bromides of strontium or calcium, and the
iodides of aluminum or magnesium. On another hand, as sea water contains
different chlorides, it results that it might serve directly as a raw
material for bleaching textile fibers. Then, when the solution of
chloride of sodium has been deprived of its chlorine by electrolysis,
there remains a solution of caustic soda which may be utilized for
scouring fibers.--_H. Danzer, in Le Genie Civil_.

* * * * *

IMPROVED SPRING TRACTION ENGINE.

Messrs. J. & H. McLaren, of the Midland Engine Works, Hunslet, Leeds,
England, for several years past have devoted considerable attention to
the question of mounting traction engines on springs. The outcome of
this is the engine in question, the front end of which is carried by a
pair of Timmis spiral springs, resting on the center pin of the front
axle, which is on Messrs. McLaren's principle, which enables it to
accommodate itself to the inequalities of the road without throwing any
undue strain on the front carriage. The chief difficulty hitherto has
been to mount the hind end on springs without interfering with the spur
gearing, which must be kept perfectly rigid to prevent breakage of the
cogs. This is entirely provided for by the new arrangement, whereby all
the spring is allowed for in the spokes of the wheel itself, which will
be clearly seen on reference to the illustrations, in which Fig. 1 is a
perspective view of the engine, while Fig. 2 shows a detail view of the
wheel. The rim of the wheel is built up in the ordinary way of strong
T-iron rings, with steel crossplates riveted on. The nave of the wheel
has wrought-iron ribs to which the spokes are bolted. These spokes are
made of the best spring steel, specially manufactured and rolled for the
purpose, 9 inches wide and 1/2 inch thick. They are bent in a pear shape,
with the narrow ends fastened to the nave, and the crown resting upon
the rim of the wheel, where they are divided, and held in their places
by means of clip fastened with bolts. When the weight of the engine
comes on these spokes, those nearest the ground are compressed and
those, at the top are elongated a little. In order to avoid any of the
driving strain passing through the springs, a strong arm is fixed on the
differential wheel and attached to the rim as shown in Fig. 2, so that
the springs have really no work to do beyond carrying the weight of the
engine. Messrs. McLaren naturally felt a certain amount of diffidence
in placing their invention before the public until they had thoroughly
tested it in practical work. This, we are informed, they have done, with
the most satisfactory results, during the last five or six months; and
they have a set of springs which ran during that time between 2,000 and
3,000 miles, besides which there are several of these spring engines in
daily use.--_Iron_.

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