32 



Dr. Gladstoue cmd the Rev. T. P. Dale on some 



From the indices given above for melted phosphorus, the fol- 

 lowing numbers may be calculated : — 



Length of spectrum 

 Dispersive power 



= 0-1878 

 = 0-1745 



These numbers are considerably less than those obtained for 

 the same element in a solid condition : indeed the decrease in 

 the dispersion would appear to be proportionally greater than 

 that in the refraction. Till, however, H is actually measured, 

 the data for an exact determination of this point are wanting. 



As with other liquids, the refractive index of melted phos- 

 phorus diminishes as the temperature increases. Our former 

 observations on the orange ray just before the fixed line D, led 

 to the formation of the following Table : — 



The sensitiveness evidently increases as the temperature rises ; 

 and it is far greater than that exhibited by any other substance 

 examined by us, with the single exception of bisulphide of car- 

 bon, which is about equally sensitive. The eflPect of changes of 

 temperature on the dispersion could not be accurately determined. 



Phosphorus, as is well known, dissolves with extreme readi- 

 ness in bisulphide of carbon. A saturated solution is almost 

 as refractive and dispersive as melted phosphorus itself: indeed 

 from one which was not perfectly saturated, the following ob- 

 servations were made : — 



These numbers are not worthy of much confidence, especially 

 at the more refracted end of the spectrum. From a somewhat 

 weaker, and therefore more manageable solution of phosphorus 

 in bisulphide of carbon, the following indices were obtained ; — 



