Qualitative Chemical Analysis From the Standpoint of Solubilities, Ionization and Mass Action

General Books publication date: 2009 Original publication date: 1913 Original Publisher: The Chemical Publishing Co. Subjects: Chemistry, Analytic Science / Chemistry / General Science / Chemistry / Analytic Notes: This is a black and white OCR reprint of the original. It has no illustrations and there may be typos or missing text. When you buy the General Books edition of this book you get free trial access to Million-Books.com where you can select from more than a million books for free. Excerpt: Chapter III SEPARATIONS When mixtures are under examination, whether it be the original substance or mixtures obtained by chemical action, it will generally be necessary to separate the constituents before they can be identified. The separation may be purely mechanical, or it may be associated with physical or chemical action. The mechanical and physical operations are here described, while those that involve chemical change are discussed under the head of reactions. Decantation. -- When a liquid containing a solid in suspension, together with substances in solution, is allowed to stand, the solid settles to the bottom of the vessel and the clear liquid may be poured away. The solid is washed by adding water, or the solvent whatever it may be, and repeating the settling and de- cantation as often as may be necessary. Filtration. -- The more common method of separating a suspended solid from a liquid is by filtration. A specially prepared filter paper is placed in a funnel and the mixture is transferred to it. The liquid runs through while the solid remains on the paper. Filtration is made more rapid by the use of the filter pump. A perforated platinum cone, or a cone of hardened paper, is placed in the funnel, the filter is neatly folded, moistened and pressed closely against the glass, and the funnel is inserted in the flask attached to the filter pump. The suction draws the liquid through rapidly and the cone prevents the breaking of the filter under the pr...