A manual of chemistry : theoretical and practical : based on Watts' edition of Fownes' Manual / by William A. Tilden.

  • Tilden, William A. (William Augustus), Sir, 1842-1926.
Date:
1897
Catalogue details

Licence: Public Domain Mark

Credit: A manual of chemistry : theoretical and practical : based on Watts' edition of Fownes' Manual / by William A. Tilden. Source: Wellcome Collection.

Provider: This material has been provided by University of Bristol Library. The original may be consulted at University of Bristol Library.

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    taste, soluble in water, and redden infusion of blue cabbage or litmus. Alkalis are more or less soluble in water. The solutions taste soapy, and they turn infusion of red cabbage or of violets green and litmus blue. Lavoisier showed that both these classes of com- pounds consist usually of oxides, and since it is commonly the property of alkalis to neutralise acids when mixed with them, the salts which result must also usually contain oxygen. Muriatic acid, however, forms an important exception to Lavoisier's rule as to the composition of acids, for it contains no oxygen. The yellow gas obtained, as already stated, by Scheele was called by him dephlogisticated mnriatic acid, a name which expressed the fact that it was mnriatic acid deprived of its inflammable principle. Lavoisier regarded it as a componnd of muriatic acid and oxygen, and it was not till 1810 that chlorine, as it was then called by Davy, was com- pletely established among the elements. Davy mixed the dry gas with hydrogen, and showed that the two unite witliout contracting and without formation of water. Charcoal intensely ignited in the gas produced no oxide of carbon, and similarly potassium, sodium, tin, copper, phosphorus, and sulphur, when ignited in chlorine, pro- duce compounds wliich have none of the properties of oxides. Other elements of similar characters have since been isolated,—iodine, by Courtois, in 1811 ; bromine, by Balard, in 1826 ; and fluorine, by Moissan, in 1886 ; and these are now recognised as forming, with chlorine, a natural group or family of elements possessing many chemical characters in common. The composition of a compound may be expressed in reference solely to the elements of which it is composed, or the proportion of those elements may be stated. During the latter half of the eighteenth century attention had been given to experiments relating to the quantity of materials to be nsed or of products obtained in chemical processes, but it was not till after Lavoisier's time that the balance was commonly used in chemical investigations. Two German chemists, Wenzel and, later, Richter, had made a great many Wenzki. analyses of salts, and had made determinations of the amount of metallic oxide required to saturate several acids, but though they did in effect establish the important principle that in chemical changes definite weights of matter are concerned, it was not till the early years of the present century that the Law of Definite Proportions was so firmly established as to be generally recognised. Proust, a Proust. French chemist, proved that native carbonate of ciq^per has the same composition as the carbonate prepared artificially by precipitation and extending similar analytical inquiries to many oxides and sulphides, he provided a secure foundation for the doctrine that every chemical compound is definite in its nature, the ratio of the elements entering into its composition being fi.xed and invari- able. From the days of Newton various attempts had been made to apply the doctrine of atoms to the explanation of the properties of matter, but owing to a lack of exact knowledge of the composition of