Intelligence and Miscellaneous Articles. 477 



ON THE ALTERATION OF THE VOLUME OF SOME SUBSTANCES BY 

 HEATING AND FUSTON. BY HERMANN KOPP. 



Previous investigations have unmistakeably shown that there 

 is a certain connexion between the specific gravity and the che- 

 mical constitution of bodies. This applies particularly to fluid 

 bodies, as with these the influence of temperature upon the volume 

 of the substance could be easily ascertained. Certain rules also exist 

 with respect to solid bodies, when their specific volumes are compared. 



The author now publishes a series of experiments, the object of 

 which was to ascertain the volume of one substance in a solid and 

 fluid state ; they also include the determination of the change of 

 volume undergone by some substances when heated or fused. He 

 gives these results as facts which may serve hereafter for the expla- 

 nation of the question, when similar observations have been made 

 upon a great number of bodies. 



The author describes his method of investigation as follows : — For 

 the determination of the expansion of solid bodies which are to be 

 fused in the course of the experiment, a fluid is required the expan- 

 sion of which is known. The methods of employing such a fluid 

 are two, — namely, 1, thermometric, in which the operation is per- 

 formed in a thermometer-like apparatus, enclosing a solid body 

 together with a fluid of known expansion, in which case the expan- 

 sion of the solid body is found by deducting that of the fluid 

 from the whole; and 2, gravimetric, in which the specific gravity of 

 the body is compared in the fluid and solid states. The author 

 prefers the former method. The fluids employed were water for 

 phosphorus, wax, stearine and stearic acid ; sulphuric acid for sul- 

 phur ; olive oil for chloride of calcium, phosphate of soda, hyposul- 

 phite of soda, and the readily fusible metallic alloys ; and oil of tur- 

 pentine for ice. 



The results of the author's experiments are as follows: — It is 

 rarely the case that a solid body exhibits the same coefficient of ex- 

 pansion when approaching its melting-point that it does when at 

 some distance from it ; the coefficient of expansion usually increases 

 rapidly towards the melting-point. Amongst the substances here 

 investigated, it is only with phosphorus, and according to other 

 observers, ice, that the degree of expansion does not increase di- 

 stinctly towards the melting-point. 



The increase of volume exhibited by a melted body when com- 

 pared with the same body at a lower temperature, arises mostly 

 from the large expansion which the substance undergoes on ap- 

 proaching the melting-point whilst still in the solid state, and from 

 its sudden expansion at the moment of fusion. In some bodies only 

 one of these expansions is of particular importance : thus, for in- 



vol. iii. p. 59, &c); and nearly two years before the paper referred to by 

 M. Becquerel was communicated to the Academy of Sciences, Mr. Faraday 

 ikoovered the magnetic properties of oxygen. (See a letter addressed on 

 this and kindred subjects to Mr. Richard Taylor, Phil. Mag. vol. xxm. p. 401.) 

 In a note bearing date the 28th of November, I860, Mr. Faraday states 

 his own claims with reference to this subject. (See Exp. lies. vol. iii. 

 p. 219.)— Ed. Phil. Mag. 



