BPTRODUCnOH 7 



quantity of matter, it follows that no one has ever succeeded in observ- 

 ing a disappearance of matter or its appearance in fresh quantities. 

 The law of the indestructibility of matter endows all chemical investi- 

 gations with exactitude, as, on its basis, an equation may be formed for 

 every chemical reaction. If in any reaction the weights of the sub- 

 stances taken be designated by the letters A, B, C, &c., and the 

 weights of the substances formed by the letters M, N, 0, &c., then 



A + B + C + = M + N + O + 



Therefore, should the weight of one of the acting or resultant sub- 

 stances be unknown, it may be determined by solving the equation. 

 The chemist, in applying the law of the indestructibility of matter, 

 must never lose sight of any one of the acting or resultant substances. 

 Should such an oversight be made, it will at once be remarked from 

 the sum of the weights of the substances taken being unequal to the 

 sum of the weights of the substances formed. All the progress made 

 by chemistry during the end of the last, and in the present, century is 

 entirely and immovably founded on the law of the indestructibility of 

 matter. It is absolutely necessary in beginning the study of chemistry 

 to become familiar with the simple truth which is expressed by this 

 law, and for this purpose several examples elucidating its application 

 will now be cited. 



1. It is well known that iron rusts in damp air, 1 ' 2 and that when 

 heated to redness in air it becomes coated with scoria (oxide), having, 

 like rust, the appearance of an earthy substance resembling some of the 

 iron ores from which metallic iron is extracted. If the iron is weighed 

 before and after the formation of the scoria or rust, it will be found 

 that the metal has increased in weight during the operation. 13 It 



development of the principles of inductive reasoning enunciated by Bacon and Descartes 

 in their philosophical treatises. Shortly after the death of Newton, Lavoisier, whose 

 fame in natural philosophy should rank with that of Galileo and Newton, was born on 

 August 20, 1743. The death of Lavoisier occurred during the Reign of Terror of the 

 French Revolution, when he, together with twenty-six other chief farmers of the revenue, 

 was guillotined on May 8, 1794, at Paris, but his works and thoughts have made him 

 immortal. 



12 By covering iron with an enamel, or varnish, or with unrustable metals (such as 

 nickel), or a coating of paraffin, or other similar substances, it is protected from the air 

 ami moisture, and so kept from rusting. 



1 Such an experiment may easily be made by taking the finest (unrusted) iron filings 

 (ordinary tilings must be first washed in ether, dried, and passed through a very fine 

 sieve). The filings thus obtained are capable of burning directly in air (by oxidising or 

 forming rust), especially when they hang (are attracted) on a magnet. A compact piece 

 of iron does not burn in air, but spongy iron glows and smoulders like tinder. In 

 making the experiment, a horse-shoe magnet is fixed, with the poles downwards, on one 

 arm of a rather sensitive balance, and the iron filings are applied to the magnet (on a 



