LUelligetice and Miscellaneous Articles. 149 



ON sodium: by m. serullas. 



If potassium is put on a mercury bath, the fragments remain for 

 some time motionless ; they afterwards, during amalgamation, begin 

 a movement, which gradually increases and becomes very rapid. This 

 movement depends upon the absorption and decomposition of the 

 moisture of the atmosphere by the metal, from which results the 

 evolution of hydrogen, which occasions the movement ; when potas- 

 sium is placed in contact with mercury under a receiver containing 

 dry air, the amalgamation goes on quietly. 



If on the other hand a particle of sodium be quickly thrown upon 

 mercury, it is violently projected out of the bath, occasioning a slight 

 explosion, accompanied with heat and light. MM. Gay Lussac and 

 Thenard have already observed that during the amalgamation of 

 sodium, heat and light were given out. It is also well known that 

 potassium burns in contact with water, while sodium decomposes it 

 without combustion. 



Thus the distinguishing characters of sodium and potassium are, 

 that the first combines with mercury with heat and light, and the 

 other merely with heat ; that sodium decomposes water without 

 burning, and that potassium under similar circumstances occasions 

 vivid light. It will be observed that in these two cases, each metal 

 possesses opposite properties. The last-mentioned effect is owing to 

 the greater heat occasioned by potassium, which even reaches incan- 

 descence, while with sodium the heat is not sufficient to occasion 

 inflammation. The proof of this will be found in the following 

 experiment, by which sodium may be made to burn by the contact of 

 water. 



Make a moderately strong mucilage of gum-arabic, and the sodium 

 when thrown upon it readily inflames. The fragments are retained by 

 the density of the liquid, and fixed to a point, and then become suffi- 

 ciently hot to ignite, and run over the surface of the liquid in the 

 same manner as potassium. The flame is yellowish instead of blue- 

 ish, as with potassium. This effect cannot be produced upon water 

 or a moistened body, which by its nature abstracts the heat pro- 

 duced by the decomposition of the liquid. Indeed if a piece of so- 

 dium be fixed upon a piece of wood or other bad conductor, and then 

 touched with a drop of water or two, it inflames and flies immediately; 

 but this efi'ect is not produced upon glass or porcelain. 



GEOLOGICAL ARRANGEMENT OF BRITISH FOSSIL SHELLS. 



In tlie sixth Number of the Magazine of Natural Uistorij, Mr. R. 

 C. Taylor has published a series of approximate stratigrajjhical tables 

 of IJritish fossil tcstacea ; forming an abstract of a more extended 

 index, constructed chiefly from Sowcrby's Mineral Conclwlogy , and 

 from authentic details, after essential corrections in the localities and 

 formations. These tables exhibit the gcognostical distribution of 

 about thirteen hundred s|)ecies ; and, from the caution employed in 

 constructing them, tliis is probably considerably short of the actual 

 number known to collectors. 



Mr. Taylor deduces various interesting results from his investiga- 

 tions, 



