230 Intelligence and Miscellaneous Articles* 



cohol of Lamy* is far too costly. The solution of silico-tungstate of 

 sodium f, of metatungstate of sodium $, and of soluble tungstic acid§ 

 as obtained by dialysis, all promised good results from their extra- 

 ordinary densities ; but all proved difficult to prepare in a state of 

 purity, and extremely easy of decomposition. 



A solution of phosphorus in bisulphide of carbon has, according to 

 Messrs. Dale and Gladstone ||, a dispersion of 0*225% or nearly one 

 and a half times as great as bisulphide of carbon alone, but becomes 

 turbid on exposure to sunlight from the formation of amorphous 

 phosphorus. It occurred to me that, by dissolving sulphur with the 

 phosphorus, the formation of amorphous phosphorus might be pre- 

 vented ; and experiment proved that this was the case. The solution, 

 as thus obtained, has a pale yellow colour, but is perfectly clear and 

 undergoes no change by the action of light even when long continued. 

 I have been in the habit of preparing it by dissolving one part of dry 

 flowers of sulphur and two parts of phosphorus in four or five parts 

 of bisulphide of carbon, and filtering the liquid through a well-dried 

 ribbed paper filter, which is easily done. The refractive and disper- 

 sive power of the solution will of course vary with the quantity of 

 phosphorus and sulphur dissolved. By a gentle heat the whole, or 

 nearly the whole, of the bisulphide of carbon may be driven off, a 

 liquid compound of sulphur and phosphorus remaining, which has so 

 high a mean refractive power that it cannot be employed with prisms 

 having a refractive angle of more than 45°-50°. The same end may, 

 however, also be attained by continually adding phosphorus to a 

 saturated solution of sulphur in bisulphide of carbon, in which phos- 

 phorus appears to be soluble without limit. 



"With a strong and probably saturated solution of sulphur in CS 2 

 the angle between Li and D was 0° 50' 10". "When phosphorus was 

 added the angle was 2° 25' 30", the refracting angle of the prism 

 being 60°. In this last case the angle between Na t and JSTa 2 was 

 0° 2' 20". The spectrum was perfectly clear, the definition of the 

 dark lines leaving nothing to be desired. In consequence, however, 

 of the yellow colour of the liquid, there is always a marked absorption 

 of the violet end of the spectrum. 



In working with the above described solution I have employed 

 hollow glass prisms with refracting plates cemented on with a mix- 

 ture of glue and molasses. These were found to be perfectly tight 

 and to last for months without change. The great disadvantage in 

 the use of a solution of sulphur and phosphorus consists in the danger 

 of breaking the prisms, the liquid taking fire spontaneously when it 

 has been a few seconds in contact with any porous material like wood 

 or paper. On the other hand, however, the large quantity of sulphur 



* Ann. de Chimie et de Physique, 4th series, vol. iii. p. 373. 

 t Ibid. p. 5. 



X Scheibler in Journal fur Prakt. Chimie, vol. lxxxiii. p. 273. 

 § Graham in Journal of the Chemical Society, vol. ii. p. 318. 

 || Phil. Mag. S. 4. vol. xviii. p. 30. 



«jl The number 0*225 is the difference between the indices for the extreme, 

 red and violet rays. 



