IMPROVEMENTS IN THE ESTIMATION OF METALS
Year: 1872

page_text: LETTERS PATENT to Joseph Norman Lockyer, of Finchley Road,
in the County of Middlesex, Esquire, a Fellow of the Royal Society,
for the Invention of "IMPROVEMENTS IN THE ESTIMATION OF METALS.”
23
Sealed the 27th May 1873, and dated the 18th December 1872.

page_text: 2. I then prepare a number of standard alloys containing the metals,
the quantities of which in an unknown mixture have to be determined.
3. I mount these standards in a special circular arrangement, by
means of which each standard can readily be brought into the required
position.
4. I then employ the standards in turn and the unknown mixture as
the electrodes between which the spark passes.
5. I then observe the spectrum of the spark passing between these
electrodes; I determine by means of the spectral lines which standard
corresponds in spectrum and therefore in composition with the unknown
mixture.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Joseph Norman Lockyer in the Great. Seal Patent
Office on the 18th June 1873.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOSEPH
NORMAN LOCKYER, of Finchley Road, in the County' of Middlesex,
Esquire, a Fellow of the Royal Society, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the, Eighteenth day of December, in the
year of our Lord One thousand eight hundred and seventy-two, in
the 36th year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto me, the said Joseph Norman Lockyer,
Her special license that I, the said Joseph Norman Lockyer, my
executors, administrators, and assigns, or such others as I, the said
Joseph Norman Lockyer, my executors, administrators, or assigns,
should at any time agree with, and no others, from time to time and
at all times thereafter during the term therein expressed, should and
lawfully might make, use, exercise, and vend, within the United
Kingdom of Great Britain and Ireland, the Channel Islands, and Islo
of Man, an Invention for "IMPROVEMENTS IN THE ESTIMATION OF METALS,"
upon the condition (amongst others) that I, the said Joseph Norman
Lockyer, my executors or administrators, by an instrument in writing
under my hand and seal, should particularly describe and ascertain the
nature of the said Invention, and in what manner the same was to be
performed, and cause the same to be filed in the Great Seal Patent Office

page_text: WE SIA CONena monens next and immediately after the date of the
said Letters Patent.
NOW KNOW YE, that I, the said Joseph Norman Lockyer, do hereby
declare the nature of my said Invention, and in what manner the
same is to be performed, to be particularly described and ascertained in
and by the following statement, reference being had to the accompanying
Drawings and to the letters and figures marked thereon, that is to
say:―
My said Invention relates to a new process of estimating metals by
employing apparatus such as is herein-after described so as to enable the
per-centage of constituents of a metallic alloy or mixture to be practically
ascertained by means of spectrum analysis applied as herein-after
mentioned.
My process is based upon the principle that a change in the per-
centage of any constituent of such metallic alloy or mixture ordinarily
causes a change in the character of lines exhibited in the resulting
spectrum in length, brightness, and thickness, or in some of these
particulars, and tho per-centages may be determined by comparison
with the spectra of known standards.
In the practical application of my improved process of estimating
metals I employ apparatus which I will proceed to describe, or equivalent
arrangements of apparatus which will enable me to observe and compare
with the spectra of standards the spectrum lines which occur in the
particular cases under examination. In some instances it is most con-
venient to compare brightness, in others thickness, in others length, in
others combinations of these several variations. When .changes in the
spectrum lines take place, consequent upon a change in the constitution
of the alloy or mixture, the proportions of constituents of the alloy or
mixture will be capable of being determined with more or less nicety by
the process aforesaid, the degree of closeness to be obtained depending
upon the amount of change in the lines brought about by a change in
the proportions of the constituents, and upon the homogeneity of the
compounds.
1. I use an electric spark to volatilize the alloy or mixture under
examination, and by means of a lens throw the image of the spark on

page_text: the slit of a spectroscope of sufficient dispersive power. This may be
any form of instrument by which a spectrum can be suitably produced
whether by refraction or diffraction.
2. I then prepare a number of standard alloys or mixturs containing
known constituents corresponding to those the proportions of which
have to be determined in an unknown alloy or mixture.

page_text: In using this apparatus I proceed as follows:-
1. I throw an image of the spark on the slit c of the spectroscope
(see Figure 1 of my Drawings), because by this means the varying
changes in the spectra, in cases in which they occur, may be best
determined by means of the varying lengths, thicknesses, and brightnesses,
or any of these characteristics of the different lines observed.
2. In the preparation of the standard alloys or mixtures referred to
care must be taken that they are well mixed; this can be approximately
determined by an examination of their spectra, the same lines getting
longer or shorter, thicker or thinner, brighter or less bright in regular
order with the continual increase or decrease of the same constituent
in cases where a difference of spectrum depending upon difference of
composition exists.
3. The special circular arrangement herein-before referred to, and
shown at A in Figure 1, is convenient, because it readily permits of the
fulfilment of conditions necessary to ensure the successful employment
of the aforesaid process, namely, that the conditions under which the
observations are made in any one series of determinations shall be
practically identical with reference to the position and distance of the
lens B and clectrodes with regard to the spectroscope, the length and
position of the spark, and the power and direction of the current; in
fact all the conditions brought into play except the constitution of the
alloy or mixture. So long as these conditions are fulfilled any equiva-
lent arrangement of apparatus having the same object in view will scrve
the purpose.
The aforesaid circular arrangement consists of a whccl-shaped disc
of brass or other convenient metal A, furnished with an edge flanged.
vertically, as shown at e in section Figure 1. Around the periphery are
screwed a number of clips or springs f, which press against the aforesaid
flange, and serve thereby to securely hold the standards and specimens
of unknown alloys or mixtures to be observed. The form of a standard
or specimen is shewn detached in side clevation and edge view at Figure 2.
Beneath the central portion of the disc A a portion of the metal is removed,
forming a circular depression or recess, as shown by the dotted lines at h
in Figure 1. This serves to receive the upper part of a convenient
support i, upon which the disc can be rotated for the facility of bringing
cach standard and specimen y in turn under the electrodo a; so as to

page_text: The successive examination of the standards referred to will indicate
which spectrum line or lines is or are most liable to change, and
therefore most suitable to be observed at each point of per-centage
composition.
Among the ways in which the changes in the spectrum lines will
make themselves apparent are the following:-
(a). A change may be observed in the length of a line or lines
belonging to one or other of certain constituents. In the diagrams
shewn in the annexed Drawing, Figures 3, 4, 5, 6, 7, the clements
to which the several lines belong, and the wave lengths are indicated by
symbols and figures. (Figures 3 and 4 shew a change in a part of the
spectrum of the light given out by the vapour of alloys of zinc and
cadmium. Figure 5 shews a similar change in one of the lines of the.
spectrum given out by certain alloys of silver and copper.)
In Figures 3 and 4 it is the fixed wire of the micrometer, and B the
moveable wire of the same. In Figure 3 the reading is +1000 = 54
per cent. cadmium. In Figure 4 the reading is +700 = 50 per cent.
cadmium.
The positions of the moveable micrometer wire B in both these dia-
grams indicate respectively the points at which the line of cadmium
commences to thin out prior to disappearance.
In the diagram, Figure 5, 3 observations are given, the position of the
extreme tip of the line being measured.
Thus +1100908 parts silver per 10,000.
"
+750 = 920
"
"
"
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"
+550923.5
"
"
"
"
The addition of silver increases the volatility of the mixture.
(b). Changes in the positions of certain characteristics of compared
lines may be observed, for instance, a change from a lower to a higher
position, or vice versa, of the level at which two adjacent lines belonging
respectively to different constituents in a mixture of two metals are
equally bright or equally thick, or both, either nearest the base or
nearest the tip of the linc. A change of this kind is shown in the
diagram of a part of the spectrum of the light given out by the vapour
of the alloys of gold and copper (Figure 6).

page_text: In this diagram six different readings are given of the levels at which
the adjacent lines of gold and copper, An 5230 and Cu 5217, are
cqually bright and thick. A is the fixed wire of the micrometer, and
1, 2, 3, 4, 5, and 6, the six positions of the moveable wire :—
1 Reading -160 = 916-7 parts of gold per 1000.
2
3
4
5
6
-120=916.6 "
-65=916.5
-10= 916.4
ور
3
"
"
"
"
"
"
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"
"
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"
"
"
"
+90=916.3;
+260 916.2
"
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I may here remark that the points or ends of the adjacent gold and
copper lines observed are always seen, but in order to represent all the
readings in one diagram they have been carried right across. The
positions of the moveable micrometer wire in this diagram shew the
points nearest the tips at which the spectrum lines are equally bright and
thick; in other analogous observations they may show sometimes equal
brightness, sometimes equal thickness, and sometimes both, as the case
may be.
(c). Observations may be made of changes in the thickness or bright-
ness of a line or lines at the same point in the field of view, such change
in the thickness or brightness being determined absolutely or by com-
parison with other lines visible at the same time, such lines belonging
cither to another constituent of the alloy or mixture, or to air or any
other medium in which the observations may be made.
(d). A change may be observed in the length of a line or lines
estimated by comparison with other lines, as in (c). A change of this
kind is shewn in the diagram of a part of the spectrum of the light
given out by the vapour of the alloy of gold and silver (Figure 7). In
this diagram four observations are given, the lines 1, 2, 3, and 4 showing
the positions of the moveable wire of the micrometer reading (1) +100
showing the most gold, whilst 4, +1400, shews the least gold. The
addition of gold reduces the volatility of the mixture. The position of
the top of the silver line nearly coinciding with an air line a is estimated
and measured by the increased apparent brightness of that air line (a)
with reference to the neighbouring air line (a').
(e). A change in the lengths, brightnesses, and thicknesses, or any of
these may be observed in the case of one constituent.

page_text: A change of this kind is observed in the spectrum of the light given
out by mixtures of copper and oxygen.
•
(f). A thinning, or shortening, or lengthening of certain lines taken
in conjunction with the fading out of others may be observed. For
example: In the case of small quantities of silver in lead, varying from
five per cent., the silver line at wave-length 5208-7 and the lead line at
5201·0 fade out in conjunction with an alteration of the length of the
lead line at 5206.5 under certain conditions of the spark. In this case
it is convenient as in some others to observe the edge of the spark.
The aforesaid and other variations in the spectra, &c., may be con-
veniently observed by means of a micrometer, reticulated eye-piece, or
other arrangement of the same nature attached to the eye end of the
observing telescope of the spectroscope, or other equivalent arrange-
ments may be adopted as may be convenient, care being taken that they
provide means which will enable simultaneous and successive observa-
tions of two or more spectra to be made for the purpose of comparison.
In some cases I employ means which will enable the spectra to be
recorded by the aid of photography.
In many cases, especially where very accurate observations are needed,
as when alloys known to be near the same point of per-centage compo-
sition have to be estimated, it is convenient to construct a curve, similar
to the one given in Figure 8, from observations of the standards, the
co-ordinates of the curve being per-centage composition and micrometer
reading of characteristic observed.
The micrometer-reading of the specimen will at once shew on what
part of the curve it is to be placed, and opposite to this reading will be
sccn the composition of the specimen.
In the diagram, Figure 8, at A, B, C, are shewn the places on the
curve of micrometer readings of three supposed unknown alloys. The
line a, b, contains the micrometer scale or readings, and the line a, c, tho
parts of gold per 10,000 as indicated by assay. A reads +175, B reads
+200, and C reads +250. The corresponding compositions of these
alloys are therefore as follows :—

page_text: In order that the mode in which the diagrams, Figures 3, 4, 5, 6, and
7 were obtained, and the mode in which analagous diagrams may be
obtained as required may be understood, I may here state that the said
diagrams represent actual observations made under the following
conditions:-
:-
A small induction coil giving a four inch spark, and Leyden jar, and
5 pint Grove cells were used.
5
The spark varied in length from 6mm in the case of some alloys to
2mm in the case of others, and a lens was employed which caused the
image of the spark on the slit plate to be about twice as large as the 10
spark itself.
Four dense flint prisms were used, one of 60, the others of 45.
The power of eye-piece in the observing telescopic was about 80.
Having now described and particularly ascertained the nature of my
said Invention, and the manner in which the same is or may be used or 1
carried into effect, I would observe in conclusion, that what I claim as
the Invention secured to me by the herein-before in part recited Letters
Patent is,-
First. The novel process of estimating the per-centage of constituents
of metallic alloys or mixtures by the aid of the spectroscope, used 20
substantially in the manner and for the purpose herein-before described.
Second. The use or manufacture, for the purpose of estimating the
per-centage of constituents of metallic alloys or mixtures, of apparatus
constructed and arranged substantially as above described.
In witness whereof, I, the said Joseph Norman Lockyer, have to 25
this my Specification set my hand and seal, the Eighteenth day
of June One thousand eight hundred and seventy-three.