A Process for Directly Obtaining the Caustic Lyes and Ammonia and Earth Alkaline Hydroxides by Electrolysis.
Year: 1899

page_text: Date of Application, 19th Oct., 1899-Accepted, 19th Oct., 1900
COMPLETE SPECIFICATION.
A Process for Directly Obtaining the Caustic Lyes and Ammonia
and Earth Alkaline Hydroxides by Electrolysis.
I, CARL LUCKOw, Junior, of Palmstrasse 36, Köln, in the Empire of Germany,
Manufacturer, do hereby declare the nature of this invention and in what manner
the same is to be performed to be particularly described and ascertained in and
by the following statement :--
This invention relates to the production of
1. The lyes, i.e. the solutions of the hydroxyl (OH) compounds of the alkaline
metals, called also alkaline hydroxides, or caustic (pyrotic) alkalies, chiefly pot-
assium K-KOH-and sodium Na-NaOH.
2. Of ammonia NH, and
3. The lyes of the earthy alkaline metals, the so-called caustic (pyrotic) earthy
alkalies or alkaline earths, especially of barium Ba-Ba (OH), and of strontium
Sr-Sr (OH)2.
from the solutions of their easily soluble salts, as electrolytes.
+
At the same time, hydrogen H is gained as a bye-product of the electrolysis.
It is well known that several years ago caustic lyes of the alkaline metals were
produced by the aid of the electric current, and as a matter of fact, by the electrolysis
of aqueous solutions of the alkaline chlorides (chloric alkalies), and this process,
especially with regard to the obtention of potassic lye (potassic hydroxide) was
completely successful. In the case of solutions of the alkaline chlorides in water
H₂O, their originally normal electrical (±) molecules break up more
or less
completely into two equal dissimilar molecules (ions) charged with free electricity,
namely on the one hand, into the electronegative (-) chlorine ions (anions) and on
the other hand, into the electropositive metal ions (kathions) that is potassic chloride
KCl into
and K. and sodic chloride NaCl into and Na, and so on.
As soon
as free electricity now collects around an electrode immersed in such a salt solution
these free products of dissociation exchange places in the medium of solution as a
result of electrostatic attraction and repulsion, and hereby cause the electrolytic
current conduction. Chlorine therefore separates at the positive electrodes (the
anodes) and the alkaline metals at the negative electrodes (the kathodes) and the
latter at once actively react on the solution medium, so that not the metals but the
aqueous solutions of their hydroxides appear at the kathode zone accompanied by the
formation of hydrogen. So simple however as this process may appear, yet important
obstacles prevent its application when working on a large scale. After the laborious
surmounting of many difficulties, combined with high pecuniary expenditure, the
factories carried on on the basis of this process keep their methods as secret as
possible. As far as is known, these up till now worked exclusively KCl, as the
electrolysis of NaCl is less profitable, because K possesses a considerably higher
combining .e. atomic weight than Na, and the price of NaOH is far lower than that
of KOH.
On account however of the solubility and great facility of making compounds of

page_text: the caustic alkalies, the production of their lyes were without exception done by the
following electrolytic methods:
(a) The employment of finely porous partitions (diaphragms) possessing a high
interior resistance, between the electrodes. These diaphragms have to permit of the
passing through of the ions but have nevertheless to completely prevent permeation
and therefore a mechanical intermixing of the kathode and anode liquids and have
also to be impervious to the influence of Cl, caustic alkalies, and the employed
temperatures, and have to be of sufficient stability to avoid fracture. In practice
plates of hard porcelain matter are principally used for this purpose of at least 5 mnm.
in thickness.
() The use of aqueous solutions of only such electrolytic salts of the alkaline
metals, the anions of which (the electronegative acid groups) volatilize during the
period of the electrolysis i.e. are liberated at the insoluble or hardly soluble anodes,
and there escape in gas form. For working this on a large scale, only the pure or
sufficiently purified, refined and cheap chlorine compounds of K and Na, firstly the
more valuable KCl and secondly the cheaper NaCl (cooking salt, rock salt) could be
used as electrolyte salts.
(c) As platinum (Pt) on account of its high price, cannot be used for large
factories, only the purest, densest and therefore compressed artificial carbon can be
used as insoluble or hardly soluble material for the anodes. Although this carbon in
general has little chemical affinity for Cl, such anodes must in the end, as a result of
their porosity soon break on account of inner gas formation and undergo an early
decay because the carbon greedily absorbs and condenses great quantities of chlorine
gas as it cannot be obtained in ideal compact condition and also the oxygen
simultaneously generated at the positive pole combines with the carbon to form
carbonic oxide CO and carbonic acid gas (carbonic dioxyde) CO₂.
The present invention differs fundamentally from all such electrolytic processes
which are in principle founded on these conditions and were only practically capable
of being carried out with success that:
(a) Diaphragms with high internal resistance are avoided so that by using the
same electrolyte i.e. KCl or NaCl in concentrated aqueous solutions, the resistances
in the bath in this case are only very slight.
(b) Soluble anodes are used, the substance of which (metals) on account of their
electrolytic dissolution (ionising) combine with the anions to form such salts as are in
the electrolyte insoluble or hardly soluble. The current therefore does not set the
anions free at the positive pole, even though they may of their own account volatilise,
but rather binds them more and more on to anode metals, which are of course in a
condition of continued ionizing, to form with them such salts, which by reason of
their nature (insolubility, or difficult solubility, high specific gravity) separate from
the electrolyte as more or less finely divided precipitates.
(c) In the nearly unlimited employment as electrolytic salts of all easily soluble
compounds of the alkalies, including ammonium and the alkaline earths whether
they be purified (refined) or crude salts or more or less strongly alloyed (impure) bye
or waste products of the industries and so on. There is only a limit in the case of
the corresponding calcium Ca salts in aqueous solution on account of the difficult
solubility of calcium hydroxide CaOH, in H₂O.
The most important and characteristic features of the present invention are found
in the electrodes and the collective adjustment of the apparatus, the electrolyte the
current, and the method of working, as follows :
THE ELECTRODES.
The electrodes throughout consist of metals and are preferably arranged not as
hitherto beside each other, but rather over each other at distances of from 15 to
20 mm. Each place of decomposition however receives only one pair of electrodes in
a vertical direction as the anode has to lie below, and the kathode above. On account

page_text: possible surface to the current, to which end, the electrodes, suitably shaped, are
more or less extended in height.
As anodes all metals which are able, after dissolution by the current, to form with
the anions such salts which are insoluble or hardly soluble in the electrolyte are in
general employed. With the exception of the alkaline metals, which as is well
known, are characterized by the small number of their hardly soluble compounds, all
other metals for more or less numerously such salts, and especially the majority of
the basic salts possess these properties. On account of their easy solubility, one
naturally finds the salts of all acids profusely represented under the widely spread
compounds of alkaline metals which represent the inexhaustable and most multifarious
sources for electrolytes. The weaker acids, i.e. those which have a lower degree of
electric dissociation and which therefore also provide a smaller number of free (+)
charged hydrogen ions, e.g. aqueous carbonic acid (hydric carbonate) carbonic hydrate
(H,CO) boracic (boric) acid HBO,, hydric cyanide (prussic acid) HCN (HCy) and so
on, together with the remainder of the metals as a rule form the hardly soluble salts;
whilst the stronger acids i.e. those which possess a higher degree of electric dissociation
and therefore provide a greater number of hydrogen ions e.g. hydro-chloric acid,
(hydric chloride, muriatic acid) HCl, chloric acid (hydric chlorate) HCIO3, sulphuric
acid H₂SO, nitric acid (azotic acid) HNO, and so on, together with the same form
easily soluble neutral and acid salts wherein however the exceptions are numerous,
but on the other hand hardly soluble subsalts. As, added to this, in this invention
the greatest inducement to the generation of negatively charged monad hydroxyl
OH ions is offered by the electrolytic dissociation of free bases; basic salts fall off
readily and frequently from this process at the positive pole. The greatest possible
chances for the formation of insoluble or hardly soluble salts therefore exist in this
invention. The invention therefore permits all the metals and especially the techni-
cally important ones, the most of the so-called heavy metals, i.e. those the specific
gravity of which is over 5 such as lead, copper, silver, zinc, iron, and so on, and their
alloys to be employed as material for the anodes with the exception of alkaline and
earthy alkaline metals, which decompose H₂O even at low temperatures under the
formation of caustic lyes.
In order that, after their generation, the insoluble or hardly soluble salts may be
precipitated out of the electrolyte as sediment as soon as possible, their liberation
from the surfaces of the anodes on which, or in the more or less direct neighbour-
hood of which they originate must be facilitated as much as possible by the con-
struction of the anode bodies and the nature of their surfaces. For the anode bodies
it is best to combine large, smooth, and more or less vertical surfaces, the anodes
having considerable width with sufficiently open interstices (gaps) running through
them, especially in a vertical direction. According to the shape of the tank for
electrolysis, so the suitable forms of the anode bodies can be diversified, for
instance,
Grates with vertical bars,
Systems of metal plates, which latter according to their height, stand vertically
to each other side by side with intervening spaces varying from about 10 to
20 mm.
Or spirally formed, or rolled strips or bands of suitable width of strong and
massive sheet metal with intermediate gaps running through between the metal
sheets, measuring from about 10 to 20 mm. according to the breadth of the strips
and the height of the anodes.
Or cylindrical bodies formed out of sheet metal, arranged in coil form with the
same spaces between, or spirals of thick metal wire or round metal rods (screw or
spiral springs, especially wire springs) and so on supply suitable forms for the
anodes.
As kathodes, those metals and metal alloys in general are usable which offer
resistance against the strong alkaline or ammonical lyes, as in the first case, Fe,
nickel Ni, Cu, Ag, and in the latter Fe, Pb. The chief requisite however, for the
kathodes is that they have the greatest possible surface, which in general is achieved

page_text: by carrying open and continuous channels and gaps of small diameter in great
number from all sides through the kathode body, so that the same receives a
comparatively large extension in height. For this kathode body therefore, thin, and
finely perforated metal sheetings, and nets, plaits, tissues, and weavings of fine
metal wire with narrow meshes are suitably employed for instance:
Spirally shaped broad strips of the above mentioned sheeting with at the most
about 5 mm. free interstices, or better still spirally shaped, very broad strips of the
mentioned wire nets, loosely rolled together can be used or high cylinders of these
sheets or nets surrounding each other with at the most about 5 mm. intermediate
spacings, or
Systems of plate shaped sheeting of the above described kinds perpendicularly,
such plates standing side by side with the same intervals, and so on, would be
suitable.
The raw salts, produced by the mines, are however often compounds (double salts)
of K and (Na) salts with the easily soluble salts of other metals, which compounds
are by the current segregated at the kathode as insoluble or hardly soluble
hydroxides. As a rule, the potassic salts especially are poluted in more or less
degree with magnesium (Mg) salts. In order therefore that by the electrolysis of such
potassic salt solutions the magnesium hydroxide Mg (OH) produced on the kathode
may easily be again removed from the kathode surface with the aid of the hydrogen
generating there, and that it may not choke up the kathode body, the previously
described conditions of construction for the anode are in this case reasonably
applicable to the kathode; that is to say, a relatively greater extension of the
kathode in height, and generally thin cross-sections of the metal body, but having
the smoothest possible surface and spaces of at least about 10 mm. passing right
through it in a vertical direction.
ARRANGEMENT OF THE APPARATUS.
A fit arrangement of the vessels and utensils, particularly adapted to smaller
works, in which the temperature of the electrolyte does not need to rise much above
50° C., and where-in electrolytic salts are worked which do not possess too many
impurities, is described as follows, reference being had to Fig. 1 of the accompanying
drawing which is a vertical section through the middle of the apparatus.
The most important vessel, the actual electrolyte receiver, .e. in which the process
of electrolysis takes place, has the shape of a large bottomless bottle tilted on its
head and having a thickset wide neck. The bottle is in two parts. The lower part
a which includes the neck, and the thereon adjoining shorter cylindrical portion of
the bottle, is made of common stone ware; serves in the main to receive the anode
and is therefore termed the anode chamber or receiver. The upper part 6 includes
the main body of the bottle cylinder, and is a cylinder of iron; and as it receives the
kathode it is called the kathode chamber or container and therefore serves for the
preparation of the caustic lyes and ammonia.
There is in a, close above the neck of the bottle, a round aperture for the up-
wardly bent pipe c which is funnel shaped at the top; it is made of the same sub-
stance as a in which it is firmly packed by means of an indiarubber tightening ring
or packing washer c¹; the indiarubber used at this, as well as at all other places is
first of all vulcanized, then desulphurated and lastly treated with paraffin. The
electrolyte receiver containing the salt solutions serving as electrolytes is fed through
c and through this also are run the middle strips, bands, wires, rods, and so on, which
are to conduct the positive current to the anodes.
The bottle, together with its mouthpiece, is on supports; and through the medium
of the indiarubber tightening ring or packing washer d, b rests on a. The ring in
which a ends at the top together with the iron hoop d¹ running outside, close over
the lower edge of b which also rests firmly on d as also the paraffined packings also
serve to complete the close fitting between a and b. The packing between a and b
is shown in large scale in Fig. 2.

page_text: under the surface of the liquid, and for the glass pipes n² and nt and so on, which
admit the non-absorbed gases to escape. In order to bring the ammonia into the
greatest possible intimacy with the greedily absorbing liquids, and to prevent a
splashing over of the latter through the arising of large and over active hydrogen
bubbles, bags o¹ 02, and so on, of a fine or close texture of thin glass threads are
arranged over the lower ends of n¹ n³, etc.
The electrolyte receiver, through the medium of the short iron tube p and both
the rubber tightening rings q and q¹ rests on the wooden filtration barrel s; and for
the further support of the electrolyte receiver, a suitable wooden frame is provided
which carries the ring cushion. The pipe p which connects a with 8, is at its
centre provided with an iron cock p¹.
The barrel has above its floor a second perforated wooden flooring (a filter
flooring) s¹ over the entire upper surface of which the filtering fabric 82 is spread
which similarly to d¹ serves for retaining all the solid insoluble substances contained
in the electrolyte; especially of course the insoluble and hardly soluble salts,
indicated by dots on the drawing which, whilst the process is proceeding come in a
more or less finely divided condition from the anode, and collect as sediment &³ over
the filtration floor. The short pipet which can be turned off by the iron tap t¹ is by
means of the rubber ring u introduced into the bung hole between the two floors to
let off the clear salt solutions.
The iron pipes e², 3, and so on, connected by the iron screw collars vv, serve as
extension of e, and under seclusion from the air, lead the caustic lyes, which can at
the most have but a medium density (concentration) to iron vessels. In order to
give the caustic lyes a higher density, in which state they are of oily consistency or
to entirely withdraw the ammonia from lyes containing ammonia, they are evaporated
in the iron vessel w which is usually silvered or silver plated inside, and is heated
by a burner x. The iron cover w¹, is fastened on to the vessel by means of the
flange w², and has in the centre a round orifice provided with a female screw into
which an iron pipe y to let off the steam, is screwed. Similarly the pipe e, which
feeds w with fresh lye and which is provided with a cock e5, is screwed into the wall of
the vessel, close under the cover, as is also the short iron pipe 2 through which the
concentrated lyes can be drawn off by means of the tap 21. Besides, w, w¹³, w², y, z,21,
e and e5 are also silvered on their insides.
By such or similar arrangement of the apparatus as described the process can be
practically carried out. On account of the nature of the process, especially as regards
the electrolyte, it would take much space to enter into details of description or
special constructions for every separate case for smaller or greater works, for lower
or higher temperatures, and so on. If, for instance, the actual electrolytic salts are
impurified by easily soluble salts or metals the hydroxides of which do not form
caustic lyes, as is often the case as regards raw salts, and bye or waste products of
the industries, the respective apparatus requires to be adapted for separating also the
insoluble or hardly soluble hydroxides falling from the kathode.
THE ELECTROLYTE.
As electrolytes, solutions of the salts of the alkaline metals, including ammonium
will serve and the earthy alkaline metals (metallic alkaline earths) either if they are
simple salts, or double salts, or salt mixtures, either with each other or with salts of
other metals or compounds or mixtures with other matters such as sugar, glycerine,
and so on, as are found abundantly in nature, or as they remain as bye or waste
products, more or less alloyed, from the industries, or as they are employed in more
or less purified or pure condition in all technical branches.
For example, there are for electrolytes, inexhaustable sources, such as sea-water,
mineral and spring water, marine salines, the water from salt lakes, salt springs, and
salt rivers, and deep and widely diffused salt deposits (Stassfurt, Kalusz and so on)
As electrolytes, solutions of the salts of the alkaline metals, including ammonium
will serve and the earthy alkaline metals (metallic alkaline earths) either if they are
simple salts, or double salts, or salt mixtures, either with each other or with salts of
other metals or compounds or mixtures with other matters such as sugar, glycerine,
and so on, as are found abundantly in nature, or as they remain as bye or waste
products, more or less alloyed, from the industries, or as they are employed in more
or less purified or pure condition in all technical branches.
For example, there are for electrolytes, inexhaustable sources, such as sea-water,
mineral and spring water, marine salines, the water from salt lakes, salt springs, and
salt rivers, and deep and widely diffused salt deposits (Stassfurt, Kalusz and so on)
waste salts, volcanic and decomposition products of nitrogen-containing organic
matters (saltpetre), the sweat of sheep's wool in the animal kingdom, in the vegetable

page_text: A round orifice, provided with a female screw, is bored close under the upper edge
of b, to receive the iron pipe e provided at both its ends with screw threads which is
intended as an outlet for the caustic lyes; the outlet is regulated by the iron
cock e¹.
Where the bottle cylinder ends into the neck, is a paraffined wooden cross piece f
of triangular cross section which carries the anode g and its current conducting
band h. The anode is fitted up as shown in the accompanying drawings Figs. 3, 4
and 5 in the following manner: a sufficiently long strip g' of rolled sheet lead, on
one end of which a band ' of sheet lead is soldered, is rolled together to a cylindrical
spiral with a uniform clear space between the spiral walls, whilst the band is bent
over so that it can be led as nearly through the middle of e as possible; g³ and h²
show the anode with its conducting band in plan, g³ and h³ show the anode and the
connecting band in lateral elevation as seen somewhat from below. g, therefore has
a suitable height and diameter corresponding to the breadth and length of the strip.
The kathode i is constructed in a similar manner to g and consists of a loose web
of iron or steel wire, as is shown in large scale in Figs. 6 and 7; this metal web is
produced by letting each pair of neighbouring wires of the chain from left to
right alternately lie over each other and securing the woof wires at the point of
crossing fixedly between them, so that the four cornered openings formed between the
crossed chain and the woof are all equally large. A sufficiently long strip of such a
wire texture is rolled up, giving a highly porous cylindrical kathode body, as is shown
in the drawing by zig-zag lines, is held together by a spiral wire running around out-
side it. The diameter of the kathode therefore corresponds to the length, and the
height of the same to the breadth of the woven strip. For the sake of clearness the
cross sections of the woven strip are only partly enlarged, and represented with clear
spaces. As suspending contrivance k for the kathode, a so called latin is employed
made by the welding or forging together of two iron bands, which equidistantly from
the point of crossing are uniformly bent loopwise and then upwards in the form of a
plate edge; whilst the projecting end of the longer iron band ¹ serves solely to
conduct the current further. This suspension contrivance is secured at as many
points of contact as possible to the kathode body by iron or steel wire stretched
tightly so that the contact between i and k is as sufficient and intimate as possible.
The kathode hangs on the indiarubber ring which is tilted up on the upper edge
of b so as to insulate the kathode from b.
The entire under surface of the rubber ring d is spanned by the filter or porous
cloth d' which only serves to hold back solid and not dissolved substances, such as
impurities and especially the produced insoluble or hardly soluble salts from the
kathode chamber. This finely porous body has therefore to permit of fluids passing
unhindered through it and must therefore not be confused with a diaphragm.
In order to keep the carbonic acid gas of the air away from the caustic lyes arising
in the kathode chamber and at the same time to take up the gases, ammonia and
hydrogen generated at the negative pole, b is covered over at the top with a hood /
which ends in the middle in a round opening, and is on its lower edge provided with
four excisions fitting exactly the four iron bands of k; it fits air tightly on k² and k,
and when necessary the fissures are filled with paraffin.
By means of the rubber packing washers m, m³, m², m³, mt, and so on, the glass
elbow pipes n, n¹, n², n³, n, and so on, connect up with the indefinitely long row of
stone-ware bottles or jugs 11, 12, etc., which are filled up to not more than the height
of the handles shewn, with distilled water and various acids in order to gradually
entirely absorb the ammonia, which besides hydrogen, escapes at the kathode, to
gain thereby aqueous ammonia (ammonia hydroxide) NH, OH, and salts of ammonia,
whilst the hydrogen is received in a gasometer. m runs out downwards into a bag o
the walls of which are copiously perforated to allow of the gases liberated at the
negative pole passing through unhindered, and which is filled up with short fine iron
or steel filings (cuttings) so as to hold back any fine drops of lye that may have been
dragged over by the hydrogen generation of the kathode. m², mt, and the like are
doubly bored plugs for the glass pipes n¹, n³ and so on, which conduct the gas to

page_text: kingdom the sap and especially the ashes of land, coast, and sea-plants, beet molasses,
and numberless other raw bye and waste products of the industries and so on.
The very best solution medium for electrolyte salts and the medium for the motions
of their free ions is naturally water on account of what one may call its dissociating
power, but the employment of other solutions, either alone or diluted with water, is
not to be excluded as far as their chemical qualities allow in the practice of a
sufficient electrolytic dissociation of the dissolved matters, together with a sufficient
electrolytic conductivity.
In general a criterion for the density of the electrolyte is given when the same has
reached a highest possible degree of electrolytic conductivity for the practice. For
the present invention therefore, that salt solution is preferable as an electrolyte,
which like NACI in aqueous solution shows simultaneously with its saturation also
the maximum of electrolytic conductivity and so, all the salts of the alkalies and of
ammonium with the mono-basic acids i.e. the most important electrolyte salts are
already in concentrated aqueous solutions relatively far advanced in the separation of
both their ions, so that salt solutions approach more or less this preferable electrolyte.
Although therefore as a rule more or less concentrated or saturated solutions are
employed as electrolytes, according to the varied solubility of the electrolyte salt in
the solution media, yet it must be noted that also more or less diluted salt baths i.e.
electrolytes of every possible density can be utilized provided of course their electro-
lytic conductivity is utilisable in practice.
In order in general to increase the solubility of most of the electrolytic salts in
their solution media, and especially of the hydroxides of the earthly alkaline metals
Ba and Sr in water as much as may be, the eleelytes are according to the greater
or lesser solubility of their salts heated to temperatures differing from about 50° to
100° C. and even higher, the always refractory Ca (OH)2 however as is well known
forming an exception being more insoluble the warmer the medium is. It is besides
a recognised fact that the electrolytic conductivity of the bath gradually increases
simultaneously with a rise of temperature as a result of the further electrolytic
decomposition (dissociation) of the dissolved salts. Warm or rather hot salt solutions
which for instance have been warmed in advance either by hot water vapour (steam) or
otherwise are allowed to pass into the electrolyte receiver and even, when necessary, heat-
ing in a suitable manner, the latter itself. The temperature of the electrolyte can be
kept within due bounds, that is to say, below 50° C., especially when the electrolitic
saits and the hydroxides to be produced are distinguished by great solubility in the
solution media adopted. In any case however, the process is not to be limited to the
employment of warm and hot electrolytes but also to the use of cold electrolytes.
The solutions of the electrolytic salts react as a rule either neutrally or more or less
strongly in an alkaline fashion accordingly as the salts are stronger or weaker acids.
In the electrolyte container according to the strength of current namely at the poles
and more especially at the kathode, the reaction alters during the longer or shorter
first or starting stage of the electrolysis which extends from the time the current is
switched on until the letting out of the caustic lyes i.e. to the refilling of fresh salt
solutions, and remains approximately in this state during the further course of the
electrolysis.
In the kathode chamber of course, the electrolyte at this stage undergoes an ever
increasing basic reaction on account of the free ions suspended in the solution
medium which reaction however is not uniform throughout but in general increases
from below upwards so that thus the pyrotic force or one might say the lye-like
character of the electrolyte also grows here, particularly in the same direction; as is
known, among metals, the alkaline and earthly alkaline metals are most prominently
electropositive, and therefore their hydroxides are the strongest bases.
As an antithesis hereto, the acid components of the electrolytically dissociated salt
molecules collect in the anode chamberas soon as the current is switched on, so that,
in a direction usually from above downwards a gradually increasing zone of breadth,
varying according to the strength of the current employed is formed directly on the
anode surfaces, which zone reacts either weak acid or more or less strong acid in direct

page_text: proportion to the acids of the electrolyte salts. Until the conclusion of the first
stage of the electrolysis however, the paramount acid character of the electrolyte in
the anode chamber is gradually blunted by the acid ions separating out of the
electrolyte as a result of their combining with the anode metals, on the point of
ionizing, to form electrically neutral insoluble or hardly soluble salts, and consequently
the specific action of the free bases makes itself ever more strongly felt in the same
ratio by the production of their electronegative dissociation products, the hydroxyl
ions.
As already mentioned no important changes in the conditions of the reaction of the
electrolyte takes place ou letting out the caustic lyes and simultaneously refilling
with fresh salt solutions.
On account of the free metal ions gathering in the kathode chamber during the
first stage of the electrolysis, the electrically neutral, that is to say, the not yet
decomposed salt molecules together with the indifferent organic matters if present
i.c. the so-called non-electrolytes, are displaced from above downwards and little by
little are moved out of the kathode chainber, so that they gradually collect for the
most part in the zone, between both the electrodes where the filter is, as well as
underneath the anode.
The current intensity is as a rule only about 10 ampères per each square meter of
kathode surface, which therefore gives somewhere about 20 to 50 ampères per square
meter of anode surface; the current intensity can be raised ad libitum to double or
more, but in general it is preferable to work with a current of only moderate
intensity.
The resistance in the baths is evidently more or less different according to the
electrolytic conductivity of the same, the metals employed for the electrodes, and the
strength of the currents and the tension undergoes small variations during the first
stage of the electrolysis, through the materials separating out of the solutions, but in
the further continuation of the electrolysis it remains constant. It is however to be
remarked that in certain cases where very impure electrolytic salts are used, especially
in the case of many bye and waste products of the industries, as for example is the
case with beet molasses, the tension of the baths greatly increases as the non-electro-
lytes consist completely or nearly completely of electrically neutral molecules.
In starting working, the cocks e¹ and ¹ are first of all shut, and the tap p¹opened;
then the electrolytic salt solutions are allowed to flow in through the pipe c until
the butt 8, the pipe p, and the electrolyte receiver are so far filled therewith that the
level of the liquid has risen to within 50 mm. below the upper part of b and c. The
insoluble substance in the salt solutions, if any e.g. impurities and so on, are as far
as feasible held at a distance from the kathode chamber by the filter d¹ and fall more
or less slowly according to their specific gravity and the degree of fineness to which
they are divided.
As soon as the current circuit is closed by the electrode bands and ¹ being con-
nected to a current source by metallic contact and ionising of the anode metal takes
place as a result of the electrolytic forces now acting, i.e. the anode metal charged with
free positive electricity (+F) becomes soluble in the form of positive ions which naturally
move about in the solution medium in the direction of the current i.e. towards the
kathode. Whilst however the free metal ions (kathions) of the actual electrolyte
salts e.g. K, Na, NH, Ba, Sr, and so on, which wander to the kathode chamber b
and there collect, remain free, the free ions of the anode metals on the contrary give
up their electric charge in a more or less short time after their coming into
+ +
+
+ +

page_text: existence; the latter therefore do not in their course come within reach of the
kathode, but at their release, or after a short time, that is to say on the anode surface
or more properly in more or less direct neighbourhood of the same, they combine
with the negatively charged ions (anions) of the electrolyte salts to form electrically
neutral molecules which in the electrolyte are insoluble or hardly soluble. It is
therefore clear that these compounds are not very firmly deposited on the anode, but
rather are generated at a relatively short distance from the same. The anode
metals thus enter these compounds as foundation, and these latter can naturally be
various according to the kind of the respective anode metal, the respective acid, as
well as the proportion in which they are. On account of their high specific gravity,
these insoluble or hardly soluble salts-shown on the drawing as dots-finely divided
and in the form of either powder or chiefly flakes roll down more or less rapidly from
the anode surface through the pipe p into the depths of the bath where they collect
on the straining floor s¹ and 82 of the barrel s as a continually increasing precipitate.
Whilst therefore the electrolysis is going on, the following actions take place at
the anode:
(a) firstly the ionising of the anode metal, and
(b) secondly the re-separation of the absorbed metal in the form of insoluble or
or hardly soluble salts.
The primary action takes place as follows:
The ions freely charged with -E of strong acids which would form easily soluble
neutral or acid salts with the metals which are (the acidulators SO, NO, CIO, Cl and
so on) employed as anodes combine with the free +E charged ions of the anode
metal, and hereby compensate their electricities in equivalent amounts. The so
formed neutral or acid salts, which are naturally specifically heavier than the actual
electrolytic salts, at once dissolve in the solution medium, as a result whereof they
more or less electrolytically break up again and begin to flow down onto the
anode surfaces and again depart therefrom, so that the more or less narrow zone of
this easily soluble salt is formed directly on the anode surface.
The secondary action is caused by reason of the following circumstances:
As a result of the primary action during the early electrolytic stage the free bases
gather more and more in the kathode chamber, which bases by reason of their
electrolytic dissociation supply free OH ions in ever increasing amount. These latter
combine with the free ions of the salt zone surrounding the anode to form insoluble
or hardly soluble basic salts. Besides this the electrolyte may naturally contain ions
of weak acids as for example the radicals CO, CN (Cy), and so on, as is the case
when using mixed and impure electrolytic salts; and such radicals would without
this form insoluble or hardly soluble salts with the anode metals, so that the separa-
tion of insoluble or hardly soluble salts is explained. In order however, that the
insoluble or hardly soluble salts may not be fixedly deposited on the anode surfaces
and gradually rigidly settle thereon as crusts, by which of course the entire further
action of the electrolysis would be interrupted but rather that these salts may easily
loosen themselves from the anode surfaces in a more or less short time after their
formation the actual electrolytic salts, especially in the present invention which
chiefly uses concentrated baths, must either be exclusively the salts of stronger acids
which would form easily soluble neutral or acid salts with the anode metals employed;
or on the other hand, the salts of weak acids, which would form insoluble or hardly
soluble salts with anode metals may, when mixed with the salt of the electrolyte,
only be present in more or less small quantities, as a rule up to 10 p.c. at the most of
water free salts; or lastly the solutions of the salts of weak acids must contain
sufficient amounts of such dissolved matters preferably of organic origin which are
apt to cause or to advance a dissolution of the anodes.
It is a fact well known by experience that in the electrolytical production of
insoluble or hardly soluble salts from solid metal anodes, without the anodes being
incrusted, the salts of weak acids in the mixture of the electrolytic salts must be
proportionately greater in quantity; the more diluted the solutions are the greater
the surplus of the media of solution (H2O) the greater the dissolving and moving

page_text: power of the latter, and the more extended the electrolytical decomposition of the
used electrolytic salts.
Of course, in the present invention, the predominating acid character of the
electrolyte in the anode chamber must not, during the action of the first electrolytical
stage, be too blunted, that is, the free OH ions must not predominate over the acid-
producers, which would inevitably take place by the forming of too great quantities
of free bases. The first stage of the electrolysis must not therefore be unnecessarily
extended, but the free bases must in proper time be let off out of the kathode
chamber in regular currents and fresh salt solutions be correspondingly led to the
anode chamber.
The evils of the aforesaid crust formations on the anodes are also much weakened
by the usual higher temperature of the electrolyte, and it can also be counteracted by
suitable aids such as a repeated brushing of the anodes.
The result therefore of the electrolysis consists therein, that the acid components
of the electrolyte salts (the anions) are little by little withdrawn from the solution,
which as a rule takes place by the anions combining with the anode metals to form
insoluble or hardly soluble salts, or they are gradually decomposed or destroyed, as
for instance the unstable acids (HNO, and the organic acids). It is well known that
nitric acid during the course of the electrolysis is first reduced to nitrous acid and
this still further to ammonia NH, and that the organic acids are ultimately
decomposed to carbonic acid gas CO,.
Naturally in just the same amount as the free acidulators disappear out of the
electrolyte, the freely charged ions of the alkaline metals (including ammonium) and
the earth alkaline metals collect in the kathode chamber. On the kathode also two
actions take place, namely:
+ +
+
++ ++
Firstly, the separation at the kathode surfaces of the kathions K, Na, NH, Ba, Sr,
and so on, and secondly the decomposition of the water by the light metals deposited
on the kathode under the formation of their easily soluble hydroxides KOH, NaOH,
NHOH, Ba (OH)2 Sr (OH), and so on, and simultaneously the generation of
thereby freed electrically neutral hydrogen in the form of little bubbles on the
surfaces of the kathode. The formation of NH4OH is questionable, at all events the
NH, ion which of itself cannot exist and is also easily variable even in its compounds
resolves itself at the negative pole partly in H and partly in NH3; H, as already
mentioned, escapes there, and NH, settles partially down there, which can easily be
recognised by the smell and a part is again absorbed in the solution medium.
In the case of the electrolysis of raw salt solutions, bye and waste products, which
are more or less strongly alloyed with the salts of foreign matters, the following are
deposited on the kathode out of the electrolyte, as follows:-
(1) In the form of insoluble or hardly soluble hydroxides:
(a) Ca, belonging to the alkaline earths, on account of the difficult solubility of Ca
(OH), in H2O especially when hot and its insolubility in the alkaline lyes.
(b) Mg, out of the remainder of the light metals, and
(c) The earths or earthy metals
(d) Some of the heavy metals, e.g. manganese Mn.
(2) As metals, chiefly in spongy condition; the heavy metals in general.
On the whole however, only traces of the heavy metals or at least only very small
quantities of them occur in the most impure electrolyte salts.
When sufficient amounts of the caustic lyes have been formed in the kathode chamber
and the upper layers especially of the same are as pure as possible, the cock e¹ is opened
more or less and the lyes are permitted to flow off in regulated current through the pipes
e, e, e³, and so on, in order to treat them outside the receiver according to the known
methods for all kinds of purposes, and if need be still further purifying them through
the extraction of other volatile, soluble, or insoluble foreign matters. One naturally
lets fresh salt solutions flow into the anode chamber simultaneously with the efflux of
the caustic lyes from the kathode chamber, whereby the first stage of the electrolysis

page_text: let out from the upper part of the kathode chamber, the anode chamber being corre-
spondingly fed with fresh salt solutions ;
(10) The metals of the anode body entering as bases into the insoluble or hardly
soluble salts are from time to time renewed.
Dated this 19th day of October 1899.
HERBERT HADDAN & Co.,
Agents to Applicant, 18, Buckingham Street, Strand, W.C.