Publisher's Synopsis
This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1899 edition. Excerpt: ... upon evaporation, crystals of alum of the composition K2S04.A12(S04)3-24H20. Note--A solution should be prepared, concentrated, and poured into a shallow crystallizing dish so that the class may observe the growth of the crystals from day to day. The temperature must not fluctuate if good crystals are to be had. Crystals deposited from impure solutions contain less impurity than the solution, i. e. a less proportion; hence crystallizable soluble substances can, by repeated solution and partial recrystallization, be almost absolutely free from all impurities--excepting isomorphous substances, and those salts with which they form double salts. DETERMINATION OF ATOMIC WEIGHTS The atoms of most elements in the solid state have approximately the same capacity for heat; as their atomic weights increase, their specific heats decrease, so that the product of the atomic weight times the specific heat approximates to a constant value. The average value is 6.4. Hence, atomic weight x specific heat=6.4. "The equivalent of an element always bears some numerical relation to its atomic weight. As a rule, this relation is a simple one. With hydrogen and chlorine, equivalent and atomic weight are equal; the atomic weight of oxygen is twice its equivalent; while that of nitrogen is three times its equivalent." Elements whose equivalent and atomic weight are equal are called Monads; those whose atomic weight is twice the equivalet are called Dyads; etc. "The word Quantivalence or Valency is applied to denote generally the state of an element as regards its function as a monad, dyad, etc." The valency of an element, then, is expressed by the number of times which the equivalent is contained in the atomic weight. As the product 6.4 varies somewhat with...