682 PROCEEDINGS OF THE AMERICAN ACADEMY. 



was able to convert pyrosulphuryl chloride to chlorsulphonic acid by 

 addition of water. ^3 Heumann and Kochlin ^5 ^{^ not think that there 

 was any dehydration of chlorsulphonic acid by phosphorus pentoxide. 



Billitz and Heumann *^ in 1883 heated chlorsulphonic acid (method 

 of preparation and properties not given) with nearly equal weight of 

 phosphorus pentoxide. The product, redistilled over phosphorus 

 pentoxide, boiled at 145-147° at 724 mm., and the analysis was close 

 to the theory for pyrosulphuryl chloride. The vapor density was 

 5.89, with evidence of decomposition. Clearly the dehydration was 

 only partial. Conversely, by adding 3 grams of water to 40 grams of 

 pyrosulphuryl chloride, the product boiled at 154-158° at 723 mm., 

 reacted violently with water, and gave an analysis corresponding 

 more nearly to chlorsulphonic acid. 



Besson *8 iu 1397 studied the purification of the two bodies, but the 

 method of preparation, vapor density, specific gravity, and analyses of 

 his crude products are not given. Crude pyrosulphuryl chloride con- 

 tained chlorsulphonic acid, chlorine, sulphur dioxide, and sulphur 

 trioxide, and could not be distilled at ordinary pressure without de- 

 composition into the last three. Mercury at low temperature removed 

 the free chlorine ; at 60° took the chlorine from the compound, setting 

 free sulphuf dioxide and trioxide. At 100° in a closed tube, sulphur 

 dioxide was the only gaseous product, mercuric sulphate and chloride 

 being formed! Most of these decomposition phenomena may of course 

 be ascribed to the chlorsulphonic acid present. By using phosphorus 

 pentachloride, Besson thought to remove the sulphur trioxide and to 

 dehydrate the chlorsulphonic acid in his crude pyrosulphuryl chloride, 

 but his product boiled at 142-143° (765 mm.). Apparently, distilla- 

 tion at 15 mm. gave what he considered pure products ; pyrosulphuryl 

 chloride boiling at 53°, chlorsulphonic acid at 65°. The former gave 

 white crystals at — 39° ; the latter did not solidify at — 75°. The boil- 

 ing point of chlorsulphonic acid at 765 mm. was 152°. Besson could 

 not cause sulphuryl chloride and sulphur trioxide to unite either in 

 sunlight or at 100°. 



During the preparation of this pS,per, the completion of which has 

 been unavoidably delayed, Prandtl and Borinski *9 have proposed a 

 method for the preparation of pure pyrosulphuryl chloride which de- 

 pends on the destruction of the chlorsulphonic acid in the mixture 

 formed in the Schiitzenberger reaction. The method is considered by 

 them to obviate the necessity for use of anhydrous material and ex- 



« Ber., 16, 483 (1883). *» Compt. rend., 124, 401 (1897). 



« Zeitschr. anorg. Chem., 62, 24 (1909). 



