Other names have been in use among the earlier chemists for this same liquid.
It is not to be supposed that there are any actual bonds of union between the atoms; graphic formulae such as these merely express the hypothesis that certain of the atoms in a compound come directly within the sphere of attraction of certain other atoms, and only indirectly within the sphere of attraction of others, - an hypothesis to which chemists are led by observing that it is often possible to separate a group of elements from a compound, and to displace it by other elements or groups of elements.
The discovery of phosphorus by Brand, a Hamburg alchemist, in 1669 excited chemists to an unwonted degree; it was also independently prepared by Robert Boyle and J.
Foerster and by Pullinger; the phosphoplatinic compounds formed primarily from platinum and phosphorus pentachloride; and also the " ammino " compounds, formed by the union of ammonia with the chloride, &c., of these metals, which have been studied by many chemists, especially S.
Klaproth, and especially by Berzelius; these chemists are to be regarded as the pioneers in this branch of descriptive chemistry.
Since their day many chemists have entered the lists, new and powerful methods of research have been devised, and several new elements definitely characterized.
In the separation of the constituents of the complex mixture of oxides obtained from the " rare earth " minerals, the methods generally forced upon chemists are those of fractional precipitation or crystallization; the striking resemblances of the compounds of these elements rarely admitting of a complete separation by simple precipitation and filtration.
Unwilling to discard the strictly unitary views of these chemists, or to adopt the copulae theory of Berzelius, he revived the notion of radicals in a new form.
The germs of analytical chemistry are to be found in the writings of the pharmacists and chemists of the iatrochemical period.
To explain this result, chemists suppose that both changes can occur simultaneously, and that equilibrium results when the rate at which AB and CD are transformed into AD and CB is the same as the rate at which the reverse change goes on.
The chemical composition and constitution of guncotton has been studied by a considerable number of chemists and many divergent views have been put forward on the subject.
Soc., 1901, 23, p. 527), who, assuming the formula C24H4 6 O 20 for cellulose, showed how the nitrocelluloses described by different chemists may be expressed by the formula C24H4,..-z020(N02)s, where x has the values 4, 5, 6, ...
We thus see that, while the great anatomists, physicists and chemists - men of the type of Willis, Borelli and Boyle - were laying foundations which were later on built up into the fabric of scientific medicine, little good was done by the premature application of their half-understood principles to practice.
Gas must be supplied at 16-candle illuminating power, and is officially tested by the chemists' department of the London County Council.
From 1870 he was editor of the Journal fiir praktische Chemie, in which many trenchant criticisms of contemporary chemists and their doctrines appeared from his pen.
OFFICINAL, a term applied in medicine to drugs, plants and herbs, which are sold in chemists' and druggists' shops, and to medical preparations of such drugs, &c., as are made in accordance with the prescriptions authorized by the pharmacopoeia.
" Benzene " is the term used by English chemists, " benzol " is used in Germany, and " benzole " in France.
The term clay is often used by chemists to denote hydrated silicate of alumina (Al 2 O 3 2SiO 2.2H 2 O), of which kaolin or china clay is a fairly pure form.
The material which chemists call calcium carbonate is met with in a comparatively pure state in chalk.
This laboratory, unique of its kind at the time, in conjunction with Liebig's unrivalled gifts as a teacher, soon rendered Giessen the most famous chemical school in the world; men flocked from every country to enjoy its advantages, and many of the most accomplished chemists of the 19th century had to thank it for their early training.
The formulae of the group of substances last mentioned are in harmony with the ordinary views of chemists as to valency, but the formulae NaHg 2, NaCd 2, NaT1 2, AuAl 2 are more surprising.
Its elementary nature was imperfectly understood; and the impure specimens obtained by the early chemists explain, in some measure, its confusion with tin, lead, antimony, zinc and other metals; in 1595 Andreas Libavius confused it with antimony, and in 1675 Nicolas Lemery with zinc. These obscurities began to be finally cleared up with the researches of Johann Heinrich Pott (1692-1777), a pupil of Stahl, published in his Exercitationes chemicae de Wismutho (1769), and of N.
The analyses of modern chemists have now revealed the existence of 32 out of the 80 known elements as existing dissolved in sea-water, and it is scarcely too much to say that the remaining elements also exist in minute traces which the available methods of analysis as yet fail to disclose.
The nature of the gases evolved by coal when freshly exposed to the atmosphere has been investigated by several chemists, more particularly by Lyon Playfair and Ernst von Composi- Meyer.
Coins of foreign mints are generally submitted to examination by a committee of eminent chemists and metallurgists whose report is published in the official journals.
The college to which Hofmann devoted nearly twenty of the best years of his life was starved; the coaltar industry, which was really brought into existence by his work and that of his pupils under his direction at that college, and which with a little intelligent forethought might have been retained in England, was allowed to slip into the hands of Germany, where it is now worth millions of pounds annually; and Hofmann himself was compelled to return to his native land to find due appreciation as one of the foremost chemists of his time.
These chemists electrolyse either pure calcium chloride, or a mixture of this salt with fluorspar, in a graphite vessel which servos as the anode.
By the addition of sodium amalgam to a concentrated solution of ammonium chloride, the so-called ammonium amalgam is obtained as a spongy mass which floats on the surface of the liquid; it decomposes readily at ordinary temperatures into ammonia and hydrogen; it does not reduce silver and gold salts, a behaviour which distinguishes it from the amalgams of the alkali metals, and for this reason it is regarded by some chemists as being merely mercury inflated by gaseous ammonia and hydrogen.
Fortunately, the compounds at first examined by the chemists engaged in verifying these laws were comparatively simple, so that the whole numbers referred to above were small.
The atomic theory has been of priceless value to chemists, but it has more than once happened in the history of science that a hypothesis, after having been useful in the discovery Present and the co-ordination of knowledge, has been aban- position doned and replaced by one more in harmony with later of the discoveries.
Some distinguished chemists have thought atomic that this fate may be awaiting the atomic theory, and that in future chemists may be able to obtain all the guidance they need from the science of the transformations of energy.
It is remarkable that this theory should have gained the esteem of the notable chemists who flourished in the 18th century.
Chemists have turned phlogiston into a vague principle, ...
Chemists gradually tired of the notion of atomic weights on account of the uncertainty which surrounded them; and the suggestion made by W.
Many chemists contributed to the establishment of such a periodicity, the greatest advances being made by John Newlands in England, Lothar Meyer in Germany, and D.
The necessity for experimental demonstration and practical instruction, in addition to academic lectures, appears to have been urged by the French chemists L.
This knowledge, joined to what he had gathered by historical reading of equally unusual extent, he carefully digested and gave to the world in his Biographisch-literarisches Handworterbuch zur Geschichte der exacten Wissenschaften, containing notices of the lives and labours of mathematicians, astronomers, physicists, and chemists, of all peoples and all ages.
Although our information respecting the chemical composition of petroleum has been almost entirely gained since the middle of the 18th century, a considerable amount of empirical knowledge of the substance was possessed by chemists at an earlier date, and there was much speculation as to its origin.
Even prior to the discovery of petroleum in commercial quantities, a number of chemists had made determinations of the chemical composition of several different varieties, and these investigations, supplemented by those of a later date, show that petroleum consists of about 84% by weight of carbon with 12% of hydrogen, and varying proportions of sulphur, nitrogen and oxygen.
Other theories of a like nature were brought forward by various chemists, Mendeleeff, for example, ascribing the formation of petroleum to the action of water at high temperatures on iron carbide in the interior of the earth.
Thus at one step Pasteur gained a place of honour among the chemists of the day, and was immediately appointed professor of chemistry at the Faculte of Science at Strasburg, where he soon afterwards married Mlle Laurent, who proved herself to be a true and noble helpmeet.
His lectures, which were supplemented with practical laboratory teaching, were attended by many chemists who subsequently attained distinction.