188 Dr. Hermann Kopp on a great Regularitij in the 



statements respecting the specific weight of one and the same 

 compound frequently differing very considerably, and the un- 

 certainty which this gives rise to is greater than that resulting 

 from our ignorance of the temperature which should be taken 

 as basis when determining the density of any body. 



Let us imagine a great number of organic compounds, 

 which may be considered as analogous, arranged under the 

 following scheme : — 



where A, B, C, D, a, /3, y, 8 express certain bodies or con- 

 stant combinations of elements. 



A, for instance, may represent hypothetical anhydrous 

 acetic acid, B formic acid, C benzoic acid, &c.; « water, /3 

 oxide of aethyl, y oxide of methyl, &c. Or we may con- 

 ceive by A chlorine, by B iodine, by C sulphur, &c. ; and by 

 a. hydrogen, by (3 aethyl, by y methyl, &c. 



It is only necessary to become acquainted "with one horizontal 

 and one vertical series, to knois) the most imiportant physical pro- 

 perties of ?\\ the combinations contained in such a table. If the 

 properties of the compounds contained in one horizontal or in 

 one vertical series are hwuDn, the mere knovolcdge of one of these 

 compounds is sufficient in order to ascertain the properties of all 

 the compounds arranged in any other horizontal or vertical se- 

 ries. 



The specific weight is given by the specific volume, since 

 the atomic weights* of the compounds are taken as known. 

 If the specific volumes and the boiling points of the com- 

 pounds A + a, A+/3, A + y, &c. are known, and we are also 

 acquainted with the specific gravity and boiling point of B + «, 

 we ascertain directly the specific gravities and boiling points 

 of the bodies B + /3, B + y, B + 8. For between the specific 

 volumes and the boiling points of 



A + « and B + « 

 A + /3and B + /3 

 A + y and B + y 



B + a and D + « 

 B + /3andD + ^ 

 B + y and D + y 



A + a and A + 8 

 B + a and B+8 

 C + «and C +8 



the differences are always the same. 



• The atomic weight of carbon is taken at 7''''854 as found by Liebig 

 and Reiitenbaclier. [See our last volume, p. 210. Eurr. | 



