AN INSULATING COMPOUND FOR ELECTRICAL PURPOSES GENERALLY."
Year: 1884

page_text: I, HERBERT JOHN ALLISON, of the firm of Allison Brothers, of Chancery Lane,
London, in the County of Middlesex, do hereby declare the nature of my invention
for re AN INSULATING COMPOUND FOR ELECTRICAL PURPOSES GENERALLY." 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 certain improvements in the insulating material
patented to me May 29, 1883, N° 2651, and consists, in the use of oxides,
carbonates, silicates, sulphates and other insoluble salts of magnesium, strontium
and barium, in combination with melted rosin, to form an insulating substance for
application to any electrical construction.
The entire group of alkaline earths possesses qualities similar to the bydrate and
carbonate of calcium ana are therefore chemically equivalent to it. The group
referred to consists of the insoluble oxides, sulphates, carbonates, silicates and other
insoluble salts of magnesium, barium, strontium and calcium, any or all of which
may be employed as chemically equivalent to the carbonate of lime, in preparing
my composition.
The common rosin or colophony consists chiefly in sylvic, pinic and other
isomeric acids, and is thus adapted to combine chemically with the alkaline
element used. Any of the earths named may therefore be used alone or with
others of the same group to form the new composition with rosin alone.
My insulating material is prepared with any of these alkaline earths by reducing
the same to a powder and mixing it thoroughly with rosin in a melted state,
preferably from fifty to ninety per cent. of the entire mixture, by weight, being
formed of the mineral earth.
The composition varies in hardness with the amount of the earth employed and
may be rendered plastic by the admixture of three to five per cent. of any fixed
oil; and it may thus be adapted for coating wires, lining conduits or insulating
the parts of all kinds of electrical constructions.
The harder varieties of the material resemble an artificial stone, and when
prepared with silicate of magnesia, resist the action of sulphuric, hydrochloric and
other acids, and water perfectly.

page_text: In the manufacture of an insulating material with the carbonate or hydrate of
lime, as claimed in my former patent, I found that it was extremely difficult in
practice, to obtain either of the said ingredients, free from silicious and other
particles of foreign matter, and that the " ground chalk" sold in commerce, was
frequently adulterated with clay and other substances.
I found upon experiment that the entire group of natural insoluble alkaline
earths, namely, the oxides, carbonates, silicates, sulphates and other insoluble salts
of calcium, magnesium, strontium, and barium, were equally well adapted for use
with the commercial rosin, in preparing my improved insulating material.
The oxide of calcium with water, produces the hydrate of lime, and with
carbonic acid, the carbonate of lime, in the form of spar, chalk, marble, etc., while
the other substances most available in practice, are the silicates of magnesium in
the form of talc, asbestos, soapstone, and white and green serpentine.
The tale, asbestos and soapstone, are already largely used in manufactures, and
the waste material of these substances, can be readily obtained, as well as the
crude article, quite free from adulterations and foreign matter, and they are also
very readily and perfectly pulverized through their freedom from gritty particles.
The composition made with these latter materials, also endures the action of the
acids, much better than the insulating material made with lime, and is therefore
better adapted for use in lining primary and secondary batteries, and in other
cases where it is exposed to an acid agent.
I am aware that both rosin and lime have been combined with other ingredients
in various mixtures for insulating electrical conductors, and I do not, therefore,
claim that either of these ingredients is new in a composition for said purpose
when mixed with other ingredients, but such elements produce very different
effects when other ingredients are present in the combination; the acid and
alkaline elements, when mingled alone, producing a chemical compound distinctly
different in its character and properties from either of the separate ingredients.
As I have already claimed a similar compound of the hydrate and carbonate of
lime with rosin, in my former patent N° 2651 of 1883, I do not claim the same
herein, but excepting such special ingredients, I claim berein the entire group of
natural alkaline earths when combined with rosin in the manner herein specified.
As stated above I have found that it was very difficult to obtain pure chalk free
from silicious particles so that it could be pulverized by the use of a grinding mill,
but I find that other forms of carbonate of lime, as marble, spar, etc., are easily
ground and are easily obtained pure and I therefore claim them among the
carbonates of the alkaline earths enumerated above.
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed, I declare that what
I claim is:
1. The insulating material herein described, consisting in the carbonates, oxides
sulphates, silicates and other insoluble salts of the alkaline earths, mixed with
fused rosin in the manner and proportions substantially as set forth.
Dated the 9th day of January 1884.
HERBERT. J. ALLISON.