Improvements in Compositions for use in Telephonic Transmitter Circuits, and in the Process employed in their Production.
Year: 1893

page_text: Date of Application, 10th Oct., 1893-Accepted, 11th Nov., 1393
COMPLETE SPECIFICATION.
Improvements in Compositions for use in Telephonic Transmitter
Circuits, and in the Process employed in their Production.
Communication from abroad by ALFRED COLLINSON COUSENS, a subject of the
Queen of Great Britain, now residing at 2, Grenville Place, Boston, in the
County of Suffolk and State of Massachusetts, one of the United States of
America, Chemist.
I ALFRED GEORGE BROOKES of 55 & 56 Chancery Lane in the County of
London Chartered Patent Agent 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 a composition of matter for use in telephonic trans-
mitter circuits in place of carbon as a tension regulator or medium of variable
resistance, the said composition being used in conjunction with the diaphragm,
tympan, electrode or other mechanical and electrical devices now commonly used
in and forming a part of telephonic instruments wherein carbon in various forms is
now commonly used.
This invention has for its object the production of a composition of matter
having a variable resistance for telephonic transmitter circuits, whereby the
loudness and distinctness of sounds reproduced by the receiving instrument is
greatly increased, and a further object of the invention is the process of producing
such variable resistance composition.
In accordance therewith the invention consists of a composition of variable
resistance for telephonic transmitter circuits, containing titanium as the essential
element, substantially as will be described.
Other features of my invention will be hereinafter described and particularly
pointed out in the claim.
As is well known, carbon in various forms is now used as a tension regulator or
medium of variable resistance in telephonic transmitter circuits, either in the form
of a button which is acted upon by a membrane or diaphragm vibrated by the
sound waves formed in speaking, or the carbon is enclosed in a box-like structure
and the vibrations of the membrane are transmitted to the carbon so that an
electric current sent through the carbon will be converted into an undulatory
current.
Various devices have been used to increase the loudness and distinctness of the
sounds reproduced by the receiving instrument, and in the course of my experi-
ments I have discovered that titanium in chemical combination with other elements,
as hereinafter set forth may be used in the place of carbon as a tension regulator
or medium of variable resistance, the loudness and distinctness of the sounds being
greatly increasd.
I have discovered that titanium in chemical combination with other elements,
preferably as an alloy, or with nitrogen, forming nitrides of titanium, or combined
with oxygen to form the sesqui-oxide, Ti,O,, or in combination with nitrogen and
cyanogen, or mixtures of said chemical compounds, may be used to vary the
strength of an electric current in the same way and under the same conditions as
carbon is known to do, and the valve of such compounds for the purpose depends
largely upon the mechanical state in which they are produced and used, the best
results being obtained by me with an alloy of titanium and aluminum approxi-
mating the formula TiAl, or Ti,Al,; and when the compounds formed with
nitrogen, oxygen, or cyanogen are in an amorpheous condition, or in the form of
minute (microscopical) plates or crystals, the latter compounds in either condition

page_text: leing preferably formed upon the surface of some substance such as platinum,
carbon, iron or siliceous material, or a substance which does not melt at the
temperature at which said compounds are formed, and so too, the alloy can be
deposited upon granules of refractory material.
The platinum, carbon or other material does not act as a variable resistance
medium, nor need it be necessarily a conductor of electricity, it serving the purpose
of a mere support or nucleus for the particles of the titanium compounds, mentioned,
causing a large number of them to act collectively, it appearing that the loudness
of the sound produced by the collective action of the particles is due to weight,
the distinctness resulting from a fine state of division, that is, numerous points of
contact.
The nucleus or supporting substance when used, may be in any mechanical form
or condition such as plates or blocks, but I prefer to use small grains or granules
of the substance, which, after they have been coated with a titanium compound, as
hereinafter described, will be used in bulk.
The titanium compounds mentioned may be used alone, and when obtained in the
form of a fine powder, may be compressed or moulded into the desired form, such
as plates or buttons.
Any of the foregoing compounds of titanium may be employed or two or more of
said compounds may be combined in various proportions, but I have obtained the
most satisfactory results with the alloy of titanium and aluminum, and also with
the copper coloured nitride Ti,N, which may be formed by various well known
chemical reactions.
Titanium and aluminum combine in different proportions to form alloys, but I
have found that the desired results are best obtained by an alloy approximating the
formula TiAl, or Ti,Al,, which may be prepared by heating three parts, by weight,
of K,TiF, and one part of aluminum foil or filings, in a carbon crucible, enclosed
in a considerably larger one of earthen ware, with a cover well luted on, the space
between the crucibles being filled with charcoal powder.
This is heated for about three hours, at about the melting point of cast iron, the
resulting alloy being found as a porous, somewhat coherent, gray or slate coloured
mass, and if the operation has been properly conducted the mass will be free or
nearly free from uncombined aluminum, potassium fluoride, or other compound.
The hardness, specific gravity and electrical conductivity of the alloy may be
varied for special purposes by the addition of various other metals, such as iron,
platinum, etc. which is preferably first combined with the aluminum by heating
them together, adding the titanium salt afterwards.
As stated particles of carbon, corundum, or other refractory material may be
coated with the alloy by mixing them with the titanium salt and aluminum, and
heating as described.
To form the titanium compound upon granules, I proceed as follows:-
Take hard non-coking nitrogenous coal, powder, sift, wash and dry the same,
and mix with about five per cent., by weight, of titanic acid or an equivalent portion
of TiO, and twenty per cent. of K,CO₂, or Na,CO, place in a closed crucible and
heat to about 2700° Fahr., which is little less than the melting point of cast iron,
for about one hour.
In the reaction which ensues the potassium or sodium carbonate melts at a low
temperature and dissolves the titanic acid, which at a high temperature decomposes,
and the titanium combines with the nitrogen of the coal, the oxygen with hydrogen
and carbon to form water and carbon monoxide or dioxide; two or more nitrides
of titanium and more or less of the sesqui-oxide being formed simultaneously.
The percentage of nitrogen in the coal modifies the result, as do other substances
other than nitrogen and carbon which may be present in the coal.
When the crucible is cool the contents are washed in water and treated with hot
hydrofluoric acid to dissolve out any substances which might interfere with proper
telephonic results, and then the substances are washed in hot water and dried.
An examination under the microscope shows carbon granules coated with an

page_text: indigo-coloured substance having a copper red lustre, needle like crystals projecting
in various directions from the substance.
If the platinum is to be treated instead of carbon, I use powdered coal with
titanic acid or TiO, and potassium or sodium carbonate as in the foregoing process.
in about the same proportions, placing the mixture in a crucible in the presence of
the platinum in the form desired, and raise the temperature considerably above the
melting point of iron, and when cooled and examined the platinum is found to be
covered with copper-coloured sesqui-oxide and Ti.N.
The platinum is made crystalline and exceedingly brittle by the reaction, and if
it is present in the form of fine wire or thin foil it may be finely powdered and used
as the variable resistance composition.
I may form the composition by another process as follows:-
Take dry potassium titanium fluoride (K,TiF) or sodium titanium fluoride
(Na,TiF) (formed by dissolving titanic acid or TiO, in HF and neutralizing the
syrupy liquid with soda or potash) and add an equal weight of powdered nitro-
genous coal, and place the mixture in the bottom of an earthen crucible and place
in the top of the crucible granules of coal, platinum or iron, according to the
substance which is to be used as the nucleus or support for the titanium coating.
The granules of the nucleus substance may be about twenty times the weight of
the titanium salt in the crucible, more or less, and the crucible is luted and heated
for about one hour to substantially near the melting point of iron, or higher if
platinum be the nucleus substance.
In the reaction, the titanium salt appears to be decomposed into gaseous TiF.
(tetra fluoride of titanium) which rises to the upper part of the crucible and is
decomposed.
The titanium has a greater affinity for nitrogen at high temperatures than it has
for fluorine, and combines therewith to form Ti, N., while the fluorine combines with
the hydrogen of the coal to form hydro fluoric acid which escapes or enters the
material of the crucible.
The deposit upon the nucleus granules is of a violet or indigo colour with a copper
or golden lustre, and is more evenly deposited and with fewer needle-like crystals
than in the first process mentioned.
If coal granules are to be coated, and five percentage of titanic acid be added
thereto, brass or gold coloured Ti,N, is formed as well as Ti,N..
When iron granules are treated, care must be taken to keep the temperature
below the melting point of iron, but with platinum or coal granules, the heat is
greater.
While it is not absolutely necessary to place the nucleus granules in the top
part of the crucible above the titanium mixture, the best results are obtained by
so doing.
The nitride of titanium is easiest formed on coal granules owing to the presence
of nitrogen in the coal, and good results are obtained by using such a composition
in the transmitter circuit.
For long circuits, however, or where the tones are to be produced as loudly
as possible by the receiver, granular platinum or an alloy of platinum having a
high melting point forms the best support or nucleus substance for the titanium
nitride.
The improved result in such case appears to be due to the high specific gravity
of the platinum or its alloy, which causes the diaphragm of the transmitter
vibrating under the action of sound waves, to strike with great force against the
particles or against the material enveloping them, and the moving particles strike
others at rest or moving in opposite directions against the contact electrodes, and a
good electrical contact is made, and thereby a greater variation in the strength or
tension of the current is obtained than could be with a nucleus substance having less
specific gravity.
In carrying out the processes described, the temperature and the time of heating

page_text: vary with the quantity of the material treated, and its mechanical condition, and
also with the thickness of the crucible used.
While I have herein pointed out various proportions or percentages of the
different ingredients used in the described processes, I do not wish to confine myself
strictly thereto, as the same may be varied within quite wide limits without materially
affecting the result.
While my correspondent has obtained the best results by using a granulated
nucleus substance coated with the titanium compound, I do not wish to be
restricted thereto, as the various compounds of titanium herein before described
may be pressed into plates, blocks or any other form desired, or plates,
blocks, etcetera. of the nucleus substance may be coated or surfaced with the
titanium compound and used in various kinds of transmitters in place of carbon.
For the purposes of my invention, I consider oxygen or cyanogen to be the
equivalent of nitrogen when used to form a chemical titanium compound other than
the alloy herein before mentioned.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is
1. A composition of variable resistance for telephonic transmitter circuits, con-
taining titanium as the essential element, substantially as described.
2. A composition of variable resistance for telephonic transmitter circuits,
containing titanium as the essential element, and a nucleus or supporting substance
for the titanium, substantially as described.
3. A composition of variable resistance for telephonic transmitter circuits,
containing titanium chemically combined with a substance having a high melting
point, substantially as described.
4. A composition of variable resistance for telephonic transmitter circuits, etcetera
consisting of a chemical combination of nitrogen or its described equivalent with
titanium, substantially as described.
5. A composition of variable resistance for telephonic transmitter circuits,
consisting of an alloy containing titanium as the essential element, substantially as
described.
6. A composition of variable resistance for telephonic transmitter circuits,
consisting of an alloy of titanium and aluminum, substantially as described.
7. The process of producing variable resistance compositions for telephonic
transmitter circuits, which consists in heating powdered coal and a titanium
compound with nitrogen in the presence of a nucleus substance, to a temperature
slightly below the melting point of said substance, substantially as described.
8. The process of producing variable resistance compositions for telephonic
transmitter circuits, which consists in heating powdered nitrogenous coal and a
titanium compound, in a closed vessel in the presence of a nucleus substance, aud
raising the temperature to substantially near but below the melting point of said
nucleus substance, substantially as described.
9. The process of producing variable resistance compositions for telephonic
transmitter circuits which consists in heating K,TiF, and a metal in a closed
vessel at a temperature of about 2700° F., to form an alloy containing titanium as
the essential element, substantially as described.
Dated the 7th day of October 1202
WM. BROOKES & SON,
55 & 56, Chancery Lane, London, Agents for the Applicant.