By L.F. NILSON.
The density of thorium as obtained by reducing the anhydrous chloride by
means of sodium was found by Chydenius, 7.657 to 7.795. The author has
obtained metallic thorium by heating sodium with the double anhydrous
thorium potassium chloride, in presence of sodium chloride in an iron
crucible. After treating the residue with water there remains a grayish,
heavy, sparkling powder, which under the microscope appears to consist
of very small crystals. Metallic thorium is brittle and almost
infusible; the powder takes a metallic luster under pressure, is
permanent in the air at temperatures up to 120 deg., takes fire below a red
heat either in air or oxygen, and burns with a dazzling luster, leaving
a residue of perfectly white thoria. If heated with chlorine, bromine,
iodine, and sulphur, it combines with them with ignition. It is not
attacked by water, cold or hot. Dilute sulphuric acid occasions the
disengagement of hydrogen, especially if heated, but the metal is acted
on very slowly. Concentrated sulphuric acid with the aid of heat attacks
the metal very slightly, evolving sulphurous anhydride. Nitric acid,
strong or weak, has no sensible action. Fuming hydrochloric acid and
_aqua regia_ attack thorium readily, but the alkalies are without
action. The metal examined by the author behaves with the reagents in
question the same as did the specimens obtained by Berzelius. The mean
specific gravity of pure thorium is about 11. Hence it would seem that
the metal obtained by Chydenius must have contained much foreign matter.
The specific gravity of pure thoria is 10.2207 to 10.2198. The
equivalent and the density being known, we may calculate the atomic
volume. If we admit that the metal is equivalent to 4 atoms of hydrogen,
we obtain the value 21.1. This number coincides with the atomic volumes
of zirconium (21.7), cerium (21.1), lanthanum (22.6), and didymium
(21.5). This analogy is certainly not due to chance; it rather confirms
the opinion which I have put forward in connection with my researches on
the selenites, on certain chloro-platinates and chloro-platinites, etc.,
that the elements of the rare earths form a series of quadrivalent
metals.
* * * * *
[AMERICAN CHEMICAL JOURNAL.]
FRIEDRICH WOeHLER.
No one but a chemist can appreciate the full significance of the brief
message which came to us a month ago without warning--"Woehler is dead!"
What need be added to it? No chemist was better known or more honored
than Woehler, and none ever deserved distinction and honor more than he.
His life was made up of a series of brilliant successes, which not only
compelled the admiration of the world at large, but directed the
thoughts of his fellow workers, and led to results of the highest
importance to science.
It is impossible in a few words to give a correct account of the work of
Woehler, and to show in what way his life and work have been of such
great value to chemistry. Could he himself direct the preparation of
this notice, the writer knows that his advice would be, "Keep to the
facts." So far as any one phrase can characterize the teachings of
Woehler, that one does it; and though enthusiasm prompts to eulogy, let
us rather recall the plain facts of his life, and let them, in the main,
speak for themselves.[1]
[Footnote 1: See Kopp's "Geschichte der Chemie," iv., 440.]
He was born in the year 1800 at Eschersheim, a village near
Frankfort-on-the-Main. From his earliest years the study of nature
appears to have been attractive to him. He took great delight in
collecting minerals and in performing chemical and physical experiments.
While still a boy, he associated with a Dr. Buch, of Frankfort, and was
aided by this gentleman, who did what he could to encourage in the young
student his inclination toward the natural sciences. The first paper
which bears the name of Woehler dates from this period, and is upon the
presence of selenium in the iron pyrites from Kraslitz. In 1820 he went
to the University of Marburg to study medicine. While there he did not,
however, neglect the study of chemistry. He was at that time
particularly interested in an investigation on certain cyanogen
compounds. In 1821 he went to Heidelberg, and in 1823 he received the
degree of Doctor of Medicine. L. Gmelin became interested in him, and it
was largely due to Gmelin's influence that Woehler gave up his intention
of practicing medicine, and concluded to devote himself entirely to
chemistry. For further instruction in his chosen science, Woehler went to
Stockholm to receive instruction from Berzelius, in whose laboratory he
continued to work from the fall of 1823 until the middle of the
following year. Only a few years since, in a communication entitled
"Jugenderinnerungen eines Chemikers," he gave a fascinating account of
his journey to Stockholm and his experiences while working with
Berzelius. On his return to Germany, he was called to teach chemistry in
the recently founded municipal trade school (Gewerbschule) at Berlin. He
accepted the call, and remained in Berlin until 1832, when he went to
Cassel to live. In a short time he was called upon to take part in the
direction of the higher trade school at Cassel. He continued to teach
and work in Cassel until 1836, when he was appointed Professor of
Chemistry in Goettingen. This office he held at the time of his death,
September 23, 1882.
In 1825 Woehler became acquainted with Liebig, and an intimate friendship
resulted, which continued until the death of Liebig, a few years ago.
Though they lived far apart, they met during the vacations at their
homes, or traveled together. Many important investigations were
conceived by them as they talked over the problems of chemistry, and
many papers appeared under both their names, containing the results of
their joint work. Among such papers may be mentioned: "On Cyanic Acid"
(1830); "On Mellithic Acid" (1830); "On Sulphotartaric Acid" (1831); "On
Oil of Bitter Almonds, Benzoic Acid, and Related Compounds" (1832); "On
the Formation of Oil of Bitter Almonds from Amygdalin" (1837); and "On
Uric Acid" (1837).
Of the papers included in the above list, the two which most attract
attention are those "On the Oil of Bitter Almonds" and "On Uric Acid."
In the former it was shown for the first time that in analogous carbon
compounds there are groups which remain unchanged, though the compounds
containing them may, in other respects, undergo a variety of changes.
This is the conception of radicals or residues as we use it at the
present day. It cannot be denied that this conception has done very much
to simplify the study of organic compounds. The full value of the
discovery was recognized at once by Berzelius, who, in a letter to the
authors of the paper, proposed that they should call their radical proin
or orthrin (the dawn of day), for the reason that the assumption of its
existence might be likened to the dawn of a new day in chemistry. The
study of this paper should form a part of the work of every advanced
student of chemistry. It is a model of all that is desirable in a
scientific memoir. The paper on uric acid is remarkable for the number
of interesting transformation products described in it, and the skill
displayed in devising methods for the isolation and purification of the
new compounds. Comparatively little has been added to our knowledge of
uric acid since the appearance of the paper of Liebig and Woehler.
It would lead too far to attempt to give a complete list of the papers
which have appeared under the name of Woehler alone. In 1828 he made the
remarkable discovery that when an aqueous solution of ammonium cyanate,
CNONH_{4}, is evaporated, the salt is completely transformed into urea,
which has the same percentage composition. It would be difficult to
exaggerate the importance of this discovery. That a substance like urea,
which up to that time had only been met with as a product of processes
which take place in the animal body, should be formed in the laboratory
out of inorganic compounds, appeared to chemists then to be little less
than a miracle. To-day such facts are among the commonest of chemistry.
The many brilliant syntheses of well-known and valuable organic
compounds which have been made during the past twenty years are results
of this discovery of Woehler.
In 1823 he published a paper on secretion, in the urine, of substances
which are foreign to the animal organism, but which are brought into the
body. He discovered the transformation of neutral organic salts into
carbonates by the process of assimilation.
In 1832 he investigated the dimorphism of arsenious acid and antimony
oxide. In 1841 he made the discovery that dimorphous bodies have
different fusing points, according as they are in the crystallized or
amorphous condition.
Among the more remarkable of his investigations in inorganic chemistry
are those on methods for the preparation of potassium (1823); on
tungsten compounds (1824); the preparation of aluminum (1827); of
glucinum and yttrium (1828). In 1856, working with Ste. Claire Deville,
he discovered crystallized boron.
Analytical methods were improved in many ways, and excellent new methods
were introduced by him. Further, he did a great deal for the improvement
of the processes of applied chemistry.
With Liebig he was associated in editing the "Annalen der Chemie and
Pharmacie" and the "Handwoerterbuch der Chemie." He wrote a remarkably
useful and popular "Grundriss der Chemie." The part relating to
inorganic chemistry appeared first in 1831, and was in use until a few
years ago, when Fittig wrote his "Grundriss" on the same plan, a work
which supplanted its prototype.
The above will serve to give some idea of the great activity of Woehler's
life, and the fruitfulness of his labors. While thus contributing
largely by his own work directly to the growth of chemistry, he did
perhaps as much in the capacity of teacher. Many of the active chemists
of the present day have enjoyed the advantages of Woehler's instruction,
and many can trace their success to the impulse gathered in the
laboratory at Goettingen. The hand of the old master appears in
investigations carried on to-day by his pupils.
Woehler's was not a speculative mind. He took very little part in the
many important discussions on chemical theories which engaged the
attention of such men as Dumas, Gerhardt, Berzelius, and Liebig, during
the active period of his life. He preferred to deal with the facts as
such; and no one ever dealt with the facts of chemistry more
successfully. He had a genius for methods which has never been equaled.
The obstacles which had baffled his predecessors were surmounted by him
with ease. He was in this respect a truly great man.
Personally, Woehler was modest and retiring. His life was simple and
unostentatious. He had a kindly disposition, which endeared him to his
students, to which fact many American chemists who were students at
Goettingen during the time of Woehler's activity can cordially testify. In
short, it may be said deliberately that Woehler, as a chemist and as a
man, was a fit model for all of us and for those who will come after us.
Though he has gone, his methods live in every laboratory. His spirit
reigns in many; could it reign in all, the chemical world would be the
better for it.