analogous Selenium Substitution Product of the same. 401 



most carefully dried flowers of sulphur are successively added 

 to the pure, clear, liquid anhydride : fresh quantities of sul- 

 phur must only be added after the first portions have entered 

 into combination with the anhydride, because any excess of 

 sulphur is readily enclosed by the blue compound as it solidifies, 

 and the decomposition of the compound is thereby hastened. 

 Immediately that the sulphur comes into contact with the 

 anhydride it dissolves, with the formation of deep-blue- 

 coloured liquid drops, which settle to the bottom of the vessel. 

 The operation may be conveniently carried out in an ordinary 

 conical glass covered with the lid of a porcelain crucible to 

 prevent the admission of atmospheric moisture. After every 

 addition of sulphur the glass must be agitated, so that the 

 drops which are formed may, by striking against the sides of 

 the vessel, be spread throughout the liquid and allowed to 

 solidify in the form of a crust rather than in little round 

 masses, which are more liable to enclose portions of the 

 anhydride. 



The glass should from time to time be immersed in water 

 at a temperature of 12°-15°, in order to prevent an undue 

 rise of temperature. When about a gram of sulphur has 

 been added, and the sides of the glass are covered with a thin 

 crust of the desired compound, the excess of anhydride (which 

 should remain colourless) is carefully poured off, the last por- 

 tion being removed by exceedingly careful evaporation, carried 

 out at a temperature not exceeding that of the blood. The 

 solid substance is removed from the glass by means of a rod, 

 placed in a well-covered vessel, and preserved in as cool a place 

 as possible. 



Properties of the Blue Compound. 



When dry, this compound forms a bluish green easily 

 friable crust, consisting of an aggregate of small papillary 

 crystals which are only visible with the magnify ing-lens. 

 The compound is liquid only at the moment of its formation ; 

 it quickly solidifies, and cannot be again fused without under- 

 going decomposition. This substance decomposes slowly at 

 ordinary temperatures, and more quickly on being heated. 

 During decomposition sulphur dioxide is evolved ; and if mois- 

 ture be carefully excluded, dry sulphur remains. I have 

 not noticed the evaporation of sulphuric anhydride during 

 the decomposition of this compound. The sulphur which 

 Schweigger noticed remaining in the vessel in his experi- 

 ments was not to be traced simply to the removal of anhydride 

 which had previously been combined with it, but to the de- 

 composition of the blue compound attended with liberation 



Phil. Mag. S. 5. Vol. 1. No. 5. May 1876. 2 E 



