SCIENTIFIC MISCELLANEA. 3431 



red lead, moistened with muriatic acid. The insect, unchanged in appear- 

 ance, is then to be replaced in the drawer of the cabinet, and, in the course 

 of a few hours, it changes to a beautiful pink. If the specimen be too long 

 exposed to the action of the gas, the colour will not be developed ; and the 

 pink colour produced by one exposure, is entirely destroyed by a second. 



E. W. B. 



Herschel, who is now at the Cape of Good Hope, has turned his attention 

 to meteorological subjects, and has moved " The African literary and Phi- 

 losophical Institution" to request the assistance of its correspondents, and of 

 all who may have leisure and inclination for observations of the kind, in any 

 part of the world, to make simultaneous registers of the barometer, thermo- 

 meter, and other meteorological instruments, and of the winds and weather ; 

 likewise, the temperature of the earth at small depths, say ten or fifteen feet. 

 He proposes, in addition to the daily register, that four days in each year 

 should henceforth be especially set apart ; and that the shewings of the dif- 

 ferent meteorological instruments should be registered every hour through- 

 out the twenty -four successive hours of those stated days — viz., the 21st of 

 March, the 21st of June, the 21st of September, and the 21st of December. 

 The plan and modes of procedure are published in a small pamphlet of 

 seventeen pages, which is printed for private distribution. 



BiCARBONATEs OF SoDA AND PoTASH Rose has shewu that bicarbonate 



of soda, when in solution, is reduced, by removing the pressure of the atmos- 

 phere, to the state of sesquicarbonate ; and that bicarbonate of potash, though 

 not affected by exposure in a vacuum, in the crystalline state, is also, decom- 

 posed, if in solution. 



Chlorous Acid. — It has been a subject of discussion among chemists 

 whether bleaching powder consists of chloride of lime, or of a mixture of 

 chlorite of lime with chloride of calcium. Balard,in an able paper, advocates 

 the latter theory. He has not succeeded in procuring chlorous acid directly, 

 from bleaching powder, but has isolated it, by pouring a mixture of red oxide 

 of mercury Avith twelve times its weight of water, into vessels filled with 

 chlorine : rapid absorption takes place. The fluid, separated by filtration and 

 distilled in vacuo, furnishes weak chlorous acid, which proves to be consti- 

 tuted of two volumes of chlorine, and one volume of oxygen. He confirms 

 the statement of M. Morin, that, by the decomposition of the bleaching chlo- 

 rides, either by time or by heat, twelve atoms of oxygen are disengaged; 

 whilst seventeen proportionals of the chloride of the metallic base, and one of 

 the chlorate of the oxide remain. 



Products obtained in Organic Analysis. — Some of the foreign che- 

 mists, by treating the cyanurets with various agents, have obtained several 

 singular compounds, differing widely in their appearance and properties. 

 These, if the contrary were not previously known, might reasonably have 

 been supposed to exist in the substance under examination. These facts 



