1 1!0 Foreign Literature and Science. 



2'i. Saltpetre. — It is stated by Henri Braconnot, that the 

 stern and leaves of the common Beet when dried and burn- 

 ed, yield ashes so rich in alkah, that it mehs easily by heat, 

 and surpasses many of the commercial varieties of potash. 

 Beets which grow in a soil highly manured contain much ni- 

 tre ; those which grow in thin and sandy soils, very little. 

 The leaves of the former when tied in bundles, and hung 

 up to dry in places slightly moist, warm, and rather dark, 

 will have their leaf stalks entirely penetrated and covered 

 with an innumerable multitude of small crystals of saltpetre. 

 The nitric acid, in this case must have entirely displaced the 

 oxalic and malic acid. Is this acid formed under the influ- 

 ence of the animalised substance contained in the petioles, 

 or is it produced exclusively by the elements of the atmos- 

 phere ? The author tried in conjunction with a friend, to 

 manufacture saltpetre from the residue of the beets used in 

 a sugar factory but was not successful. — Ann. de Chimie. et 

 de Physique^ Juillet, 1827. 



25. Evaporation of water from hot surfaces. — It was as- 

 certained by Leidenfrost, in 1756, that between the boil- 

 ing point and that at which iron becomes white hot, water 

 evaporates from its surface less easily the greater the heat. 

 Klaproth repeated these experiments and relates the result 

 as follows. 



A polished iron spoon being heated to whiteness, and a 

 drop of water being let fall upon it, the drop split into pieces, 

 but these were soon united again, and appeared like a crys- 

 tal ball in a state of repose, touching the hot metal only in 

 one point. On observing it closely, it was found to turn rap- 

 idly round its center, becoming smaller and smaller until it 

 was dissipated with explosion. As soon as it was gone, he 

 let fall another, and then a third, fourth, &c. the spoon cool- 

 ing the whole time. 



The first drop continued 40 seconds, 

 the second - - 20 " 

 third . . 6 " 



fourth - . 4 " 

 fifth - - 2 " 



sixth - - " 



Having let fall seven drops in a spoon heated to the prop- 

 er point, they united in a globular mass which began to turn 

 on its axis with rapidity. It afterwards separated at the top. 



