_Introduction._
As we look back to the time of the founding of the Journal in 1818, we
see that the science of chemistry had recently made and was then making
great advances. That the scientific men of those days were much
impressed with what was being accomplished is well shown by the
following statement made in an early number of the Journal (=3=, 330,
1821) by its founder in reviewing Gorham’s Elements of Chemical Science.
He says: “The present period is distinguished by wonderful mental
activity; it might indeed be denominated as the intellectual age of the
world. At no former period has the mind of man been directed at one time
to so many and so useful researches.”
A very remarkable revolution in chemical ideas had recently taken place.
Soon after the discovery of oxygen by Priestley in 1774, and the
subsequent discovery by Cavendish that water was formed by the
combustion of hydrogen and oxygen, Lavoisier had explained combustion in
general as oxidation, thus overthrowing the curious old phlogiston
theory which had prevailed as the basis of chemical philosophy for
nearly a century.
The era of modern chemistry had thus begun, and the additional views
that matter was indestructible and that chemical compounds were of
constant composition had been generally accepted at the beginning of the
nineteenth century.
Dalton had announced his atomic theory in 1802, having based it largely
upon the law of multiple proportions which he had previously discovered,
and he had begun to express the formulas for compounds in terms of
atomic symbols.
In 1808 Gay-Lussac had discovered his law of gas combination in simple
proportions,[153] a law of supreme importance in connection with the
atomic theory, but neither he nor Dalton had seen this theoretical
connection. Avogadro had understood it, however, and in 1811 had reached
the momentous conclusion that all gases and vapors have equal numbers of
molecules in equal volumes at the same temperature and pressure.
Davy in 1807 had isolated the alkali-metals, sodium and potassium, by
means of electrolysis, thus practically dispelling the view that certain
earthy substances might be elementary; and about four years later he had
demonstrated that chlorine was an element, not an oxide as had been
supposed previously, thus overthrowing Lavoisier’s view that oxygen was
the characteristic constituent of all acids.
At the time that our period of history begins, the atomic theory had
been accepted generally, but in a somewhat indefinite form, since little
attention had been paid to Avogadro’s principle, and since Dalton had
used only the principle of greatest simplicity in writing the formulas
of compounds, considering water as HO and ammonia NH, for example. At
this time, however, Berzelius for ten or fifteen years had been devoting
tremendous energy to the task of determining the atomic weights of
nearly all of the elements then known by analyzing their compounds. He
had confirmed the law of multiple proportions, accepted the atomic
theory, and utilized Avogadro’s principle, and it is an interesting
coincidence that his first table of atomic weights was published in the
year 1818.
An interesting account of the views on chemistry held at about that time
was published in the Journal by Denison Olmsted (=11=, 349, 1826; =12=,
1, 1827), who had recently become professor of natural philosophy in
Yale College.
The most illustrious European chemists of that time were Berzelius of
Sweden, Davy of England, and Gay-Lussac of France, and the curious
circumstance may be mentioned that all three of them and also Benjamin
Silliman, the founder of the Journal, were born within a period of eight
months in 1778–1779.
In this country Robert Hare of Philadelphia and Benjamin Silliman were
undoubtedly the most prominent chemists of those days. Hare is best
known for his invention of the compound blowpipe, but his contributions
to the Journal were very numerous, beginning almost with the first
volume and continuing for over thirty years. Among the first of these
contributions was a most vigorous but well-merited attack upon a Doctor
Clark of Cambridge, England, who had copied his invention without giving
him proper credit. He begins (=2=, 281, 1820) by saying: “Dr. Clark has
published a book on the gas blowpipe in which he professes a sincere
desire to render everyone his due. That it would be difficult for the
conduct of any author to be more discordant with these professions, I
pledge myself to prove in the following pages.”
Hare also invented a galvanic battery which he called a “deflagrator,”
consisting of a large number of single cells in series. With this, using
carbon electrodes, he was able to obtain a higher temperature than with
his oxy-hydrogen blowpipe. He was the first to apply galvanic ignition
to blasting (=21=, 139, 1832), and he first carried out electrolyses
with the use of mercury as the cathode (=37=, 267, 1839). In this way he
prepared metallic calcium and other metals from solutions of their
chlorides, while the principle employed by him has in recent times been
used as the basis of a very important process for manufacturing caustic
potash and soda.
Silliman, who had become an intimate friend of Hare during two periods
of chemical study under Woodhouse in Philadelphia in 1802–1804, and who
soon afterwards spent fourteen months as a student abroad, chiefly in
England and Scotland, took a broad interest in science and gave much
attention to geology as well as to chemistry. In spite of this divided
interest and his work as a teacher, popular scientific lecturer, and
editor, he found time for a surprising amount of original chemical work.
For instance, using Hare’s deflagrator, he showed that carbon was
volatilized in the electric arc (=5=, 108, 1822); he was the first in
this country to prepare hydrofluoric acid (=6=, 354, 1823), and he first
detected bromine in one of our natural brines (=18=, 142, 1830).
_Atomic Weights._
As soon as the atomic theory was accepted, the relative weights of the
atoms became a matter of vital importance in connection with formulas
and chemical calculations. In advancing his theory, Dalton had made some
very rough atomic weight determinations, and it has been mentioned
already that Berzelius, at the time that our historical period begins,
was engaged in the prodigious task of accurately determining these
constants for nearly all the known elements. It is recorded that he
analyzed quantitatively no less than two thousand compounds in
connection with this work during his career. His table of 1818 has
proved to be remarkably accurate for that pioneer period, and it
indicates his remarkable skill as an analyst.
It is to be observed that Berzelius in this early table made use of
Avogadro’s principle in connection with elements forming gaseous
compounds, and thus obtained correct formulas and atomic weights in such
cases, but that in many instances his atomic weights and those now
accepted bear the relation of simple multiples to one another, because
he had then no means of deciding upon the formulas of many compounds
except the rule of assumed simplicity. For example, the two oxides of
iron now considered to be FeO and Fe_{2}O_{3} he regarded as FeO_{2} and
FeO_{3}, knowing as he did that the ratio of oxygen in them was 2 to 3,
and believing that a single atom of iron in each was the simplest view
of the case, so that as the consequence of these formulas the atomic
weight of iron was then considered to be practically twice as great in
its relation to oxygen as at present.
These old atomic weights of Berzelius, used with the corresponding
formulas, were just as serviceable for calculating compositions and
analytical factors as though the correct multiples had been selected. As
time went on, the true multiples were gradually found from
considerations of atomic heats, isomorphism, vapor densities, the
periodic law, and so on, and suitable changes were made in the chemical
formulas.
Berzelius used 100 parts of oxygen as the basis of his atomic weights, a
practice which was generally followed for several decades. Dalton,
however, had originally used hydrogen as unity as the basis, and this
plan finally came into use everywhere, as it seemed to be more logical
and convenient, because hydrogen has the smallest atomic weight, and
also because the atomic weights of a number of common elements appeared
to be exact multiples of that of hydrogen, thus giving simpler numbers
for use in calculations.
Within a few years a slight change has been made by the adoption of
oxygen as exactly 16 as the basis, which gives hydrogen the value of
1·008.
As early as 1815, Prout, an English physician, had advanced the view
that hydrogen is the primordial substance of all the elements, and
consequently that the atomic weights are all exact multiples of that of
hydrogen. This hypothesis has been one of the incentives to
investigations upon atomic weights, for it has been found that these
constants in the cases of a considerable number of the elements are very
close to whole numbers when based upon hydrogen as unity, or even still
closer when based upon oxygen as 16.
With our present knowledge Prout’s hypothesis may be regarded as
disproved for nearly all the elements whose atomic weights have been
accurately determined, but the close or even exact agreement with it in
a few cases is still worthy of consideration. There is an interesting
letter from Berzelius to B. Silliman, Jr., in the Journal (=48=, 369,
1845) in which Berzelius considers the theory entirely disproved.
For a long time entire reliance was placed upon the atomic weights
obtained by Berzelius, but it came to be observed that the calculation
of carbon from carbon dioxide appeared to give high results in certain
cases, so that doubt arose as to the accuracy of Berzelius’s work.
Consequently in 1840 Dumas, assisted by his pupil Stas, made a new
determination of the atomic weight of carbon, and found that the number
obtained by Berzelius, 12·12, was slightly too large. Subsequently Dumas
determined more than twenty other atomic weights, but this great amount
of work did not bring about any considerable improvement, for it appears
that Dumas did not greatly excel Berzelius in accuracy, and that the
latter had made one of his most noticeable errors in connection with
carbon.
Soon after assisting Dumas in the work upon carbon, Stas began his very
extensive and accurate, independent determinations, leading to the
publication of a book in 1867 describing his work. Stas made many
improvements in methods by the use of great care in purifying the
substances employed, and especially by using large quantities of
material in his determinations, thus diminishing the proportional errors
in weighing. His results, which dealt with most of the common elements,
were accepted with much confidence by chemists everywhere.
Stas reached the conclusion that there could be no real foundation for
Prout’s hypothesis, since so many of his atomic weights varied from
whole numbers, and this opinion has been generally accepted.
The first accurate atomic weight determination published in the Journal
was that by Mallett on lithium (=22=, 349, 1856; =28=, 349, 1859),
showing a result almost identical with that accepted at the present
time. Johnson and Allen’s determination (=35=, 94, 1863) on the rare
element cæsium was carried out with extraordinary accuracy. Lee, working
with Wolcott Gibbs, made good determinations on nickel and cobalt (=2=,
44, 1871). The work of Cooke on antimony (=15=, 41, 107, 1878) was
excellent.
Concerning the more recent work published elsewhere than in the Journal,
attention should be called particularly to the investigations that have
been carried on for the past twenty-five years by Richards and his
associates at Harvard University. Richards has shown masterly ability in
the selection of methods and in avoiding errors. His results have
displayed such marvelous agreements among repeated determinations by the
same and by different processes as to inspire the greatest confidence.
His work has been very extensive, and it is a great credit to our
country that this atomic weight work, so superior to all that has been
previously done, is being carried out here.
It may be mentioned that for a number of years the decision in regard to
the atomic weights to be accepted has been in the hands of an
International Committee of which our fellow countryman F. W. Clarke has
been chairman. In connection with this position and previously, Clarke
has done valuable service in re-calculating and summarizing atomic
weight determinations.
_Analytical Chemistry._
Analysis is of such fundamental importance in nearly every other branch
of chemical investigation that its development has been of the utmost
importance in connection with the advancement of the science. It
attained, therefore, a comparatively early development, and one hundred
years ago it was in a flourishing condition, particularly as far as
inorganic qualitative and gravimetric analysis were concerned. There is
no doubt that Berzelius, whose atomic weight determinations have already
been mentioned, surpassed all other analysts of that time in the amount,
variety, and accuracy of his gravimetric work. He lived through three
decades of our period, until 1848.
During the past century there has been constant progress in inorganic
analysis, due to improved methods, better apparatus and accumulated
experience. An excellent work on this subject was published by H. Rose,
a pupil of Berzelius, and the methods of the latter, with many
improvements and additions by the author and others, were thus made
accessible. Fresenius, who was born in 1818, did much service in
establishing a laboratory in which the teaching of analytical chemistry
was made a specialty, in writing text-books on the subject and in
establishing in 1862 the “Zeitschrift für analytische Chemie,” which has
continued up to the present time.
Besides Berzelius, who was the first to show that minerals were definite
chemical compounds, there have been many prominent mineral analysts in
Europe, among whom Rammelsberg and Bunsen may be mentioned, but there
came a time towards the end of the nineteenth century when the attention
of chemists, particularly in Germany, was so much absorbed by organic
chemistry that mineral analysis came near becoming a lost art there. It
was during that period that an English mineralogist, visiting New Haven
and praising the mineral analyses that were being carried out at Yale,
expressed regret that there appeared to be no one in England, or in
Germany either, who could analyze minerals.
The best analytical work done in this country in the early part of our
period was chiefly in connection with mineral analysis, and a large
share of it was published in the Journal. Henry Seybert, of
Philadelphia, in particular, showed remarkable skill in this direction,
and published numerous analyses of silicates and other minerals,
beginning in 1822. It was he who first detected boric acid in tourmaline
(=6=, 155, 1822), and beryllium in chrysoberyl (=8=, 105, 1824). His
methods for silicate analyses were very similar to those used at the
present time.
J. Lawrence Smith in 1853 described his method for determining alkalies
in minerals (=16=, 53), a method which in its final form (=1=, 269,
1871) is the best ever devised for the purpose. He also described (=15=,
94, 1853) a very useful method, still largely used in analytical work,
for destroying ammonium salts by means of aqua regia. Carey Lea (=42=,
109, 1866) described the well-known test for iodides by means of
potassium dichromate. F. W. Clarke (=49=, 48, 1870) showed that antimony
and arsenic could be quantitatively separated from tin by the
precipitation of the sulphides in the presence of oxalic acid. In 1864
Wolcott Gibbs (=37=, 346) began an important series of analytical notes
from the Lawrence Scientific School, and he worked out later many
difficult analytical problems, particularly in connection with his
extensive researches upon the complex inorganic acids.
From 1850 on, Brush and his students made many important investigations
upon minerals, and from 1877 Penfield (=13=, 425), beginning with an
analysis of a new mineral from Branchville, Connecticut, described by
Brush and E. S. Dana, displayed remarkable skill and industry in this
kind of work. Both of the writers of this article were fortunate in
being associated with Penfield in some of his researches upon minerals
and one of us began as he did with the Branchville work. It is probably
fair to say that Penfield did the most accurate work in mineral analysis
that has ever been accomplished, and that he was similarly successful in
crystallography and other physical branches of mineralogy.
The American analytical investigations that have been mentioned were all
published in the Journal, with the exception of a part of Gibbs’s work.
Many other American workers at mineral analysis might be alluded to
here, but only the excellent work of a number of chemists in the United
States Geological Survey will be mentioned. Among these Hillebrand
deserves particular praise for the extent of his investigations and for
his careful researches in improving the methods of rock analysis.
To our own Professor Gooch especial praise must be accorded for the very
large number of analytical methods that have been devised, or critically
studied, by him and his students, and for the excellent quality of this
work. The publications in the Journal from his laboratory began in 1890
(=39=, 188), and the extraordinary extent of this work is shown by the
fact that the three hundredth paper from the Kent Laboratory appeared in
May, 1918. These very numerous and important investigations have been of
great scientific and practical value, and they have formed a striking
feature of the Journal for nearly 30 years. In 1912 Gooch published his
“Methods in Chemical Analysis,” a book of over 500 pages, in which the
work in the Kent Chemical Laboratory up to that time was concisely
presented. Among the many workers who have assisted in these
investigations, P. E. Browning, W. A. Drushel, F. S. Havens, D. A.
Kreider, C. A. Peters, I. K. Phelps and R. G. Van Name are particularly
prominent. Besides many other useful pieces of apparatus, the perforated
filtering crucible was devised by Gooch, and this has brought his name
into everyday use in all chemical laboratories.
Volumetric analysis was originated by Gay-Lussac, who described a method
for chlorimetry in 1824, for alkalimetry in 1828, and for the
determination of silver and chlorides in 1832. Margueritte devised
titrations with potassium permanganate in 1846, while Bunsen, not far
from the same time, introduced the use of iodine and sulphur dioxide
solutions for the purpose of determining many oxidations and reductions.
We owe to Mohr some improvements in apparatus and a German text-book on
the subject, while Sutton wrote an excellent English work on volumetric
analysis, of which many editions have appeared.
While volumetric analysis began to be used less than one hundred years
ago, its applications have been gradually extended to a very great
degree, and it is not only exceedingly important in investigations in
pure chemistry, but its use is especially extensive in technical
laboratories where large numbers of rapid analyses are required.
Not a few volumetric methods have been devised or improved in the United
States, but mention will be made here only of Cooke’s important method
for the determination of ferrous iron in insoluble silicates, published
in the Journal (=44=, 347, 1867); to Penfield’s method for the
determination of fluorine in 1878; and to the more recent general method
of titration with an iodate in strong hydrochloric acid solutions, due
to L. W. Andrews, a number of applications of which have been worked out
in the Sheffield Laboratory.
A considerable amount of work with gases had been done by Priestley,
Scheele, Cavendish, Lavoisier, Dalton, Gay-Lussac, and others before our
hundred-year period began. Cavendish, about 1780, had analyzed
atmospheric air with remarkable accuracy, and had even separated the
argon from it and wondered what it was, and later Gay-Lussac had shown
great skill in the study of gas reactions. During our period gas
analysis has been further developed by many chemists. Bunsen, in
particular, brought the art to a high degree of perfection in the course
of a long period beginning about 1838, the last edition of his “Methods
of Gas Analysis” having been published in 1877.
Important devices for the simplification of gas analysis in order that
it might be used more conveniently for technical purposes have been
introduced by Orsat in France and by Winkler, Hempel and Bunte in
Germany.
It appears that our countryman Morley has surpassed all others in
accurate work with gases in connection with his determinations of the
combining weights and volumes of hydrogen and oxygen about the year
1891. Some of his publications have appeared in the Journal (=30=, 140,
1885; =41=, 220, 1891; and others).
Electrolytic analysis, involving the deposition of metals, or sometimes
of oxides, usually upon a platinum electrode, was brought into use in
1865 by Wolcott Gibbs through an article published in the Journal (=39=,
58, 1865). He there described the electrolytic precipitation of copper
and of nickel by the methods still in use. The application of the
process has been extended to a number of other metals, and it has been
largely employed, particularly in technical analyses. Important
investigations and excellent books on this subject have been the
contributions of Edgar F. Smith of the University of Pennsylvania, and
the useful improvement, the rotating cathode, was devised by Gooch and
described in the Journal (=15=, 320, 1903).
_General Inorganic Chemistry._
_The Chemical Symbols._—It is to Berzelius that we owe our symbols for
the atoms, derived usually from their Latin names, such as C for carbon,
Na for sodium, Cl for chlorine, Fe for iron, Ag for silver, and Au for
gold. We owe to him also the use of small figures to show the number of
atoms in a formula, as in N_{2}O_{5}. This was a marked improvement over
the hieroglyphic symbols proposed by Dalton, which were set down as many
times as the atoms were supposed to occur in formulas, forming groups of
curious appearance, but in some respects not unlike some of our modern
developed formulas. The advantages of Berzelius’s symbols were their
simplicity, legibility, and the fact that they could be printed without
the need of special type. It is true that at a later period Berzelius
used certain symbols with horizontal lines crossing them to represent
double atoms, and that these made some difficulty in printing. It should
be mentioned also that Berzelius at one time made an effort to simplify
formulas by placing dots over other symbols to represent oxygen, and
commas to represent sulphur atoms. Examples of these are: