A handbook of chemical analysis : (adapted to the unitary notation) / based on the fourth edition of H. Will's Anleitung zur chemischen Analyse by F.T. Conington.

  • Heinrich Will
Date:
1858
Catalogue details

Licence: Public Domain Mark

Credit: A handbook of chemical analysis : (adapted to the unitary notation) / based on the fourth edition of H. Will's Anleitung zur chemischen Analyse by F.T. Conington. Source: Wellcome Collection.

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    PxVRT I. REACTIONS OF THE NON-METALLIC ELEMENTS AND THEIR MOST IMPORTANT COMPOUNDS. Tins class of bodies comprises by far tlie greater number of those substances whicli possess an acid reaction*, and which are therefore designated by the generic name of Acids. In this part, therefore, will be found the reactions by which the great majority of acids are distinguished. But, as there are some compounds of the non-metallic elements which are not acids, so there are some acids which contain metallic elements. Since, however, the characteristic reactions of these metallic acids depend upon the presence of the metallic element, they will naturally be treated of in Part II., which is devoted to metals and their compounds.] * The general reagent by which the presence of any acid is detected, is infu- sion of litmus, the blue colour of which is instantaneously changed to red on contact with an acid. It is this property of reddening litmus which is signified when a substance is said to have an acid reaction. Conversely, a body which possesses the property of restoring the blue colour of reddened litmus, is said to have an alkaline reaction. Another general test for such acids as are soluble in water, is tlieir behaviour with carbonates, with which they cause effervescence, owing to the formation and decomposition of carbonic acid. t As the sense in which we employ tlie term acid is somewhat different from that which is prevalent in most works on chemistry, it may be well to dwell briefly on the signification that wc attach to it. Wc adopt the definition given by Gerhardt (Introduction ä I'Etude de la Chimie, p. 103) : an acid is a salt whose base consists entirehj of hydrogen. Thus, nitric acid, NO^II, is nitrate of hydrogen, just as NO^Ag is nitrate of silver. In our view, therefore, the pre- sence of basic hydrogen — i. e. of hydrogen which can be replaced by any otiier metal — is essential to the idea of an acid. Hence we hold that these bodies, whicli arc commonly called anhj/drous acids, are not acids at all; and, in fact they do not exhibit acid reactions. We propose to designate these bodies by the name anhydrides (e.g. sulphuric anhydride, SO'; carbonic onhvdride, CO-, &c). The number of atoms of basic hydrogen varies in different acids, and on this
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