SANGER-RIEGEL. — PYROSULPH. CHLORIDE-CHLORSULPH. ACID. 683 



elusion of moisture in carrying out the reaction, as recommended by 

 Konovaloff. It was clear to them, from the color reactions with tellu- 

 rium and selenium, as well as from analyses of the fractions, that the 

 two bodies were both present and could not be separated by fractiona- 

 tion. On the assumption that chlorsulphonic acid is more readily 

 attacked by water than pyrosulphuryl chloride, they treat the crude 

 distillate with ice in a freezing mixture. The lower layer of pyrosul- 

 phuryl chloride is separated from the upper of sulphuric acid, and dis- 

 tilled, with or without phosphorus pentoxide. Seventy per cent of the 

 crude pyrosulphuryl chloride was recovered, boiling at 150° (720 mm.). 

 The analysis gave almost theoretical figures, and the specific gravity 

 was 1.876 at 0° ; 1.844 at 18°. Vapor density determinations by the 

 Meyer method gave 7.15 and 7.27 (theory, 7.49). In making these, 

 the bulb of the apparatus was heated with phosphorus pentoxide before 

 adding the substance. Other trials, without this desiccation, gave 

 5.94 and 6.32. 



Prandtl and Borinski find the action of tellurium and selenium use- 

 ful in distinguishing between the two bodies, Chlorsulphonic acid 

 gives with the first a cherry red color, with the second a dark green, 

 while pyrosulphuryl chloride gives no color with either. They consider 

 that pyrosulphuryl chloride is not converted to chlorsulphonic acid by 

 water, but directly to sulphuric and hydrochloric acids. Adding five 

 grams of water to sixty grams of pyrosulphuryl chloride (equal mole- 

 cules) they obtain sulphuric acid and a distillate boiling at 140-147°, 

 which they consider to be unaltered substance, since it dissolved in 

 water slowly and was not colored by tellurium. 



Historical Summary. 



The table on the follo^ving two pages shows briefly the results ob- 

 tained by former investigators: 



The Results of this Investigation. 



It is clear, from consideration of the foregoing and from our own 

 work, that the most reliable preparations of pyrosulphuryl chloride 

 were those of Konovaloft' and of Prandtl and Borinski, while Beck- 

 urts and Otto have described the only reasonably pure preparation of 

 chlorsulphonic acid. It is evident, also, that while either body, with 

 proper precautions, may be prepared without a large admixture of 

 the other, or of the decomposition products of either, yet it is some- 

 what doubtful whether an absolutely pure preparation of either has 

 been made, especially in large quantities. Further, the widely differ- 



