3l4 Scieniijic Notices — Al/uera/ogi/. [April, 



In either case, a thin fihii of platinum is deposited upon the 

 interior of the tube, and adheres with considerable firmness. If 

 a tube thus prepared be filled with a mixture of hydrogen and 

 oxygen (or atmospheric air), and inverted over water, the whole 

 of the hydrogen will be condensed into water in the course of a 

 few hours. A similar result is obtained by placing a mass ©f 

 spongy platinum well soaked with water into a receiver filled 

 with the mixture of the two gases. He next examined what 

 would be the effect of moistening the platinum with other 

 liquids. With alcohol the experiment succeeded equally as well 

 as with water ; but not the slightest condensation took place 

 when the spongy metal was imbibed with nitric acid, or with 

 liquid ammonia. He ascribes these differences exclusively to 

 the gaseous mixture being absorbable by water and alcohol, but 

 not by nitric acid or liquid ammonia : in the former case only, 

 the gases would be conveyed into immediate contact with the 

 metal. Dobereiner concludes with observing, that the existence 

 of some peculiar and independent property in the platinum is 

 more decisively evinced by the present experiment than by any 

 other which he had heretofore made. 



These experiments suggested an easy method of depurating 

 hydrogen from minute traces of oxygen. All that is necessary 

 is to enclose it in a stoppered phial, a portion of whose interior 

 has been coated by the process just described, with a thin incrus- 

 tation of platinum. The oxygen will by degrees undergo con- 

 densation. — (Schweigger's Neues Jornalfiir Chemie and Physik, 

 xii. 60.) 



Mineralogy. 



2. Sodalite. 



A mineral, obviously intimately associated with sodaHte, has 

 been examined by Wachtmeister. It is found on Vesuvius 

 incorporated with the garnet described in p. 71. Its colour is 

 white, and it is in an imperfect degree transparent. It has a 

 granular texture, and is brittle. Before the blowpipe it melts 

 without giving off any water: it is more fusible than albite or 

 icespar, but less so than mesotype or meionite. In borax, it 

 dissolves with extreme slowness into a transparent glass. With 

 solution of cobalt, the edges become faintly blue coloured. 

 Muriatic acid cannot be detected by means of oxide of copper. 



The mineral is readily decomposed by nitric or muriatic acid, 

 gelatinous silica remaining undissolved. Its constituents were 

 found to be, 



SiUca 50-98 



Alumina 27*64 



Soda 20.96 



Muriatic acid 1-29 



100-87 



