Dr Davy's Ohservatimis on Phosphorus. 4i^ 



in the course of several hours. In others, it has shone very 

 brightly, sometimes by fits, flashes of light appearing and disap. 

 pearing ; and sometimes without interruption, with an intensity, 

 though infinitely below the violent combustion of phosphorus, 

 so much above its very slow one, that the heat produced fused 

 the phosphorus, and the ascent of the water or mercury in the 

 tube was visible in progress, and occasionally rapid, and yet 

 never breaking out into vivid inflammation. 



To what these differences of eff^ect have been owing, I have 

 not been able to ascertain ; only this far, that they were not 

 concerned with the purity of the gas, at least, in relation to the 

 presence of small variable proportions of atmospheric air, or in- 

 deed any appreciable adulteration ; or with the degrees of tem- 

 perature. The most probable mode of explanation of the lu- 

 minous appearances in different degrees is, that they are connect- 

 ed with the formation of different compounds of phosphorus and 

 oxygen, according to the analogy of the degrees of light emitted 

 by sulphur in combustion ; but of the truth of this I have not 

 been able to satisfy myself by experiment. 



In accordance with the observations of others, I have found 

 that when oxygen gas is rarefied, phosphorus shines in it ; and 

 that when condensed, it ceases to shine. With an augmented 

 pressure of a column of mercury of 16 inches, when heated with 

 a spirit-lamp in this gas, it emitted no light, till it fused ; then 

 it burst into flame and burnt explosively, and the oxygen was 

 condensed in an instant. 



Dr Ure states in his Dictionary of Chemistry, that phospho- 

 rus soon ceases to be luminous in dry atmospheric air, on ac- 

 count of the acid coat formed on it, which protects the surface 

 from the farther action of the air. This I have not found to 

 be the case.. A stick of phosphorus suspended over strong sul- 

 phuric acid in a limited portion of atmospheric air, continued 

 shining many hours, till, there was reason to suppose, all the 

 oxygen was consumed ; and the result has been the same 

 when phosphorus has been introduced into air confined over 

 mercury, and previously dried by the same acid ; when its light 

 ceased, a fresh portion of phosphorus thrown up did not kindle. 

 In both instances, the luminous appearance was as bright as in 

 common air that had not been artificially dried. 



VOL. XV. NO. XXIX. JULY 1833. D 



