Course of qualitative chemical analysis / by the late Wm. Geo. Valentin.

  • Valentin, W. G
Date:
1880
Catalogue details

Licence: Public Domain Mark

Credit: Course of qualitative chemical analysis / by the late Wm. Geo. Valentin. Source: Wellcome Collection.

    18/290 (page 4)
    or adding it to the main filtrate. These tubes are conveniently placed in a tcst- tulie stand (Pig. 4). After being well cleansed by the aid of a test-tube brush, and rinsed out with distilled water, they should be set aside to drain in a basket. Beakers are sometimes employed if an analysis involves the separation of a small quantity of one substance from a large amount of another, and when, of necessity, large quantities of the substance miist be operated upon. Poreelalii dislies are employed for the purpose of concentration, or evapora- They can be lieated either by means of a spirit lamp (Fig. 5), or by means of a Bunsen gas lamp, pro- vided with a rose top. Sometimes a sheet of iron wire gauze or a sand-bath is interposed between the porce- lain vessel and the gas flame, and is supported on a re- tort ring, or tripod stand. Illustrations of convenient tripod supports for porcelain and glass vessels, which prevent at the same time the flame from being blown ganic Chemistry.” If solid substances have to bo examined, they should always be powUcrc«l in a mortar—an agate mortar should be employed for hard substances, such as minerals—before being dissolved in water, acids, &c. Kcactions involving the use of valuable reagents—such as salts of gold, platinum, silver—should be performed on watcli-glasses, with small quantities of the substance only. For the Ignition of precipitates porcelain crucibles, or small porcelain dishes are used. A knowledge of qualitative analysis enables us— 1. To recognise with speed and certainty the presence of various elementary and compound bodies. 2. To effect their separation from each other. In order to aecomplisb this we shall study more particularly those chemical reactions—both in the dry and in the wet way which are essential; but shall endeavour, at the same time, to give as complete a view as possible of other chemical changes which serve the purposes of qualitative analysis, and which on this and other grounds possess considerable interest. It is for many reasons desirable to confine the laboratory course at first to the study of the more important elements and their coni- pounds; we shall, however, treat of the rarer elements and their compounds in an Appendix. There are certain reagents which effect the separation of a number of bodies contained in a common solution, leaving all the others in solution. Such general reagents are then called group- reagents. Dissolve in water small quantities of Argentic nitrate* Cupric nitrate. Cobaltic ,, Baric ,, Potassic „ * Solutions of salts of the different metals containing five milligrammes of the metal in a cubic centimetre are conveniently prepared and kept for use. tion and ignition.